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SMITHSONIAN SCIENTIFIC SERIES
Editor-in-chief CHARLES GREELEY ABBOT, D.Sc.
Secretary of the Smithsonian Institution
Published by
SMITHSONIAN INSTITUTION SERIES, Inc. NEW YORK
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INSECTS
THEIR WAYS AND MEANS OF LIVING,
By Ropert Evans Snopcrass United States Bureau of Entomology
VOLUME FIVE
OF THE
SMITHSONIAN SCIENTIFIC SERIES 1930
CopyRIGHT 1930, BY SMITHSONIAN INSTITUTION SERIES, Inc.
{Printed in the United States of America] All rights reserved
Copyright Under the Articles of the Copyright Convention of the Pan-American Republics and the United States, August 11, 1910
CONTENTS
PREFACE
THE GRASSHOPPER ;
THE GRASSHOPPER’S COUSINS : RoacHES AND OTHER ANCIENT INSECTS Ways ano Means oF LivinG TERMITES
Piant Lice
THE PeErtopicaL CicaDA
Insect MetTaMoRPHOSIS .
. THe CATERPILLAR AND THE Motu
MosquiToEs AND FLIEs .
INDEX
Sens FOR ROS SI TaHEe PO
eee. os SIARE SOP AOS SI ANE po
PELUS TRATIONS
LIST OF PLATES
The Carolina Locust
Miscellaneous insects
The Green Apple Aphis
The Rosy Apple Aphis
The Apple-grain Aphis . . .
Nymph of the Periodical Cicada .
Newly emerged Cicada
Cicada laying eggs .
Egg nests and eggs of the Periodical Cicada Two species of large moths.
The Cecropia Moth and the Polyphemus Moth The Ribbed-cocoon Maker
The Peach-borer Moth . .
The Red-humped Caterpillar .
The Tent Caterpillar
LIST OF TEXT FIGURES
Young grasshoppers. .
End structures of a grasshopper’ s body . Grasshopper laying eggs ; Egg-pods of a grasshopper
Eggs of a grasshopper - :
Young grasshopper ememinet from the cee Eggs of a katydid .
A young grasshopper :
The growth stages of a grasshopper :
A parasitic fly 5 is : Blister beetles
A triungulin larva of a blister beetle Second-stage larva of a blister beetle Examples of Arthropoda
A “singing” grasshopper
Another “‘singing” grasshopper
The feet of Orthoptera
Sound-making organs of a meadow grasshopper
. Frontispiece
28 154 160 170 184 192 198 212 228 230 252 254 260 262
19. 20. Auditory organ of a katydid .
21. A bush katydid . :
22. The oblong-winged katydid
23. The angular-winged katydid .
24. The true katydid
25. The katydid in various attitudes : 26. Sound-making organs of the eos 27. Aconehead katydid
28. The robust katydid eer
29. The common meadow katydid
jo. The handsome meadow katydid . 31. The slender meadow katydid .
32. The Coulee cricket . ;
33- Wings of a tree cricket
Mig Ainge Gs - . -
35. The striped ground cricket
36. The common black cricket
37- The snowy tree cricket i 38. Antennal marks of the tree crickets : 39. The narrow-winged tree cricket . 40. A broad-winged tree cricket
41. Back glands of a tree cricket .
42. The jumping bush cricket
43. The common walking-stick insect
44. A gigantic walking-stick insect
45. A leaf insect Seas?
46. The praying mantis
47. A shield-bearing mantis
48. Egg case of a mantis
49. Common household roaches
so. Eggcasesofroaches . .
51. Young of the Croton bug .
52. The house centipede
53. Wings of acockroach .
54. A Paleozoic forest .
55. Fossil roaches
56. Early fossil insects .
57. Machilis .
58. Dragonflies . . .
59. A young dragonfly .
60. A mayfly
61. A young mayfly
62. The relation of the germ cells and body cells 63. External structure of an insect 2 64. Leg of a young grasshopper
Sound-making organs and ears of a conehead katydid
. Legs of a honeybee
Head and mouth parts of a grasshopper Internal organs of a grasshopper . Alimentary canal of a grasshopper Heart of an insect .
Respiratory system of a caterpillar The brain of a grasshopper Nervous system of a grasshopper Reproductive organs of an insect Ovipositor of a race
Termites
Termite work in a piece of wood .
Worker and soldier castes and young of a termite
Heads of termite soldiers .
Winged caste of a termite . : Short-winged reproductive caste of a termite A wingless termite queen .
Termite king and queen
Wing of an ordinary termite .
Wings of a Mastotermes : Section of an underground termite nest . Four types of termite nests
Large termite nest .
Group of aphids feeding
How an aphis feeds 2
Section of the beak of an aphis
Aphis eggs
Aphis eggs just before hatching
Young aphis emerging from the egg . Young aphids on apple buds . ie Young of three species of apple aphids . Apple leaves infested by green ne itis ; The green apple aphis . ; The rosy apple aphis on apple
The rosy apple aphis on plantain
Male and female of the rosy apple aphis Some common aphids of the garden .
A ladybird beetle :
The aphis-lion ;
The golden-eye, Chry sopa :
Larva of a syrphus fly oe on aphids Adult syrphus flies .
A parasitized aphis_—.
An aphis parasite, Aphidius
A female Aphidius i inserting an egg ina living aphis
Parasitized aphids on parasite cocoons A parasitized lady-beetle larva A common cicada su Nye
106 108 109 112 115 118 120 2) 123 126 128 130 132 133 135 138 141 145 146 147 149 150 153 154 156 157 158 159 161 162 163 165 168 169 170 171 173 174 176 176 177 178 178 178 179 181 183
149. 1So.
154. 155. 156. ST
159.
Young nymph of the periodical cicada Older nymph of the periodical cicada Underground cells of the periodical cicada . Fore leg of a cicada nymph
Cicada turrets : Transformation of the cicada -
Two forms of the periodical cicada
Male of the periodical cicada .
The head and beak of a cicada
The sucking organ of a cicada
Section of a cicada’s body
Sound-making organs of a cicada
Egg and newly-hatched nymph of the cicada Young cicada nymph :
Moths of the fall webworm :
The celery ca etl and py :
The Luna moth :
Life of a cutworm
A maybeetle and its grub
Life stages of a lady-beetle
Life stages of a wasp
A dragonfly nymph
Various habitats of plant- feeding caterpillars External structure of a caterpillar
Adult and larval forms of beetles
Diagram of insect metamorphosis Springtails :
A bristletail, Thermobia
The relation of a pupa to other insect t forms Muscle attachment on the body wall Young tent caterpillars
Eggs and newly-hatched tent caterpillars First tent of young tent caterpillars . Young tent caterpillars on a sheet of silk Mature tent caterpillars feeding .
Mature tent caterpillars a: Twigs denuded by tent caterpillars .
A tent caterpillar jumping from a tree Cocoon of a tent caterpillar
Head of a tent caterpillar .
Jaws of a tent caterpillar .
Internal organs of a caterpillar
The spinning organs of a caterpillar .
The alimentary canal of a tent caterpillar Crystals formed in the Malpighian tubules . The fat-body of a caterpillar . : Transformation of the tent caterpillar
186 187 188 190 192 196 200 200 202 204 206 Beit) 220 224 DOF 229 230 DAN 233 235 236 238 241 242 244 246 247 248 254 256 263 265 267 268 271 273 278 280 282 284 284 285 287 288 289 291 294
160. 161. 162. 163. 164. 165. 166. 167. 168. 169. 170. 17. 172 IRs 174. alse 176. 177. 178. 179. 180. 181. 132. 183. 184. 185. 186.
Contents of the pupal blood
Moths of the tent caterpillar .
Head of a tent caterpillar moth Head of a peach borer moth Transformation of the alimentary canal Reproductive organs of a female moth Young tent caterpillars in the egg
A robber fly . : Wings of insects
The black horsefly .
Mouth parts of a horsefly .
Structure of a fly maggot . Rat-tailed maggots
Larva and pupa of a horsefly .
Life stages of a mosquito . Structure of a mosquito larva Mouth parts of a mosquito
A male mosquito
Mosquito larvae
Mosquito pupae :
The female malaria mosquito : Feeding positions of mosquito la1vae
Life stages of the house fly
Head and mouth parts of the koma: Hy :
Head of the stable fly . A tsetse fly .
Head and nonce parts ate thet tsetse Ay
393 3°97 308 308 310 312 313 316 317 320 322 325 326 328 330 332 334 335 Sish7/ 339 342° 341 344 346 347 349 351
INSECTS THEIR WAYS AND MEANS OF LIVING
PREFACE
In the early days of zoology there were naturalists who spent much time out of doors observing the ways of the birds, the insects, and the other creatures of the fields and woods. These men were not steeped in technical learning. Nature was a source of inspiration and a delight to them; her manifestations were to be taken for granted and not questioned too closely. A mind able to accept appear- ances for truth can express itself in the words of everyday language—for language was invented long ago when people did not bother themselves much with facts—-and some of those early writers, inspired direct from nature, have left us a delightful literature based on their observa- tions and reflections on the things of nature. The public has liked to read the works of these men because they tell of interesting things in an interesting way and in words that can be understood.
At the same time there was another class of nature students who did not care particularly what an animal did, but who wanted to know how it was made. The devotees of this cult looked at things through microscopes; they dissected all kinds of creatures in order to learn their con- struction and their structural relationships. But they found many things on the inside of animals that had never been named, so for these things they invented names; and when their books were printed the public could not read them because of the strange words they contained. More- over, since nature does not usually embellish her hidden works, the anatomists could not enhance their writings with descriptive metaphors in the way the outdoor naturalists could. Consequently, the students of struc- ture have never come into favor with the reading public, and their works are denounced as dry and tedious.
[i]
PREFACE
Then there arose still another group of inquiring minds. Members of this school could not see anything worth while in knowing merely either what an animal did or how it was made. They devoted their efforts to discovering the secrets of its workings. They invented instruments for measuring the power of its muscles, for testing the nature of the force that resides in its nerves; they made analyses of its food and its tissues; they devised all kinds of experi- ments for revealing the causes of its behavior. The work- ers in this branch, the physiologists, had to have a con- siderable grounding in physics and chemistry; conse- quently they came to write more or less in the languages of those sciences and to express themselves in chemical and mathematical formulae. Their writings are hard for the public to understand. Their statements, moreover, are often at odds with preconceived ‘ideas, since precon- ceived ideas are conceived in ignorance, and the public at large does not take to this sort of thing—it cherishes above all its inherited opinions.
Therefore the old-time naturalist is still venerated, as he deserves to be, and those who call themselves “nature lovers” still like to decry the laboratory worker as an evil being who would take the beauty from nature and destroy the soul of man. A modern writer of the old school may sell his wares, but when something goes wrong with his stomach or his nerves, or when his plants or his animals are attacked by disease, it is the knowledge of the labora- tory scientist that comes to his aid.
The reason that the specific truths of nature must be found out in laboratories is that there are too many things mixed together in the fields. The laboratory naturalist endeavors to untangle the confusion of elements in the outdoor environment and to isolate the different factors that affect the life and behavior of an animal, in order that he may be sure with just what he is dealing in his ef- forts to determine the value of each one separately. By creating a set of artificial environments in each of which
[ii]
PREFACE
only one natural factor is allowed to be operative at the same time, he is in a position to observe correctly, after repeated experiments, just what effects proceed from this cause and what from that.
Nature study, in the superficial sense, may be enter- taining. We of the present age, however, must learn to take a deeper insight into the lives of the other living things about us. Insects, for example, are not curiosities; they are creatures in common with ourselves bound by the laws of the physical universe, which laws decree that everything alive must live by observing the same ele- mental principles that make life possible. It is only in the ways and means by which we comply with the condi- tions laid down by physical nature that we differ.
Many sincere people find it difficult to believe in evolu- tion. Their difficulty arises largely from the fact that they look to the differences in structure between the diverse types of living things and do not see the unity in function that underlies all physical forms of life. Conse- quently they do not understand that evolution means the progressive structural divergence of the various life forms from one another, resulting from the different ways that each has adopted and perfected for accomplishing the same ends. Man and the insects represent the extremi- ties of two most divergent lines of animal evolution, and by reason of the very disparity in structure between us the bond of unity in function becomes all the more apparent. A study of insects, therefore, will help us the better to understand ourselves in so far as it helps us to grasp the fundamental principles of life.
Some writers seem to think that the sole purpose of writing is that it shall be read. Just as reasonable would it be to claim that the only purpose of food is that it shall be eaten. In the following chapters the reader is offered an entomological menu in which the consider- ation of nutrient value and the requirements of a balanced meal have been given first attention. As a concession to
[ ii ]
PREFACE
palatability, however, as much as possible of the dis- tasteful matter of technical terminology has been ex- tracted, and an attempt has been made to avoid the pure scientific style of literary cuisine, which forbids the use of all those ingredients whose object is that of inflation but which, if properly admixed, will greatly aid in the process of digestion.
Much of the material in several chapters is taken from articles already printed in the Annual Reports of the’ Smithsonian Institution. The original drawings of most of the color plates and line cuts are the property of the United States Bureau of Entomology, though some of them are here published for the first time.
RBS:
[iv |
INSECTS
THEIR WAYS AND MEANS OF LIVING
CHAPTER
hab GRASSHOPPER
SOMETIME in spring, earlier or later according to the lati- tude or the season, the fields, the lawns, the gardens, sud- denly are teeming with young grasshoppers. Comical little fellows are they, with big heads, no wings, and strong hind legs (Fig. 1). They feed on the fresh herbage and hop lightly here and there, as if their existence in no way in- volved the mystery of life nor raised any questions as to why they are here, how they came to be here, and whence they came. Of these questions, the last is the only one to which at present we can give a definite answer.
If we should search the ground closely at this season, it might be possible to see that the infant and apparently motherless grasshoppers are delivered into the visible world from the earth itself. With this information, a nature student of ancient times would have been satisfied —grasshoppers, he would then announce, are bred spon- taneously from matter in the earth; the public would believe him, and thereafter would countenance no con- trary opinion. There came a time in history, however, when some naturalist succeeded in overthrowing this idea and established in its place the dictum that every life comes from an egg. This being still our creed, we must look for
the grasshopper’s egg. ad
INSECTS
The entomologist who plans to investigate the lives of grasshoppers finds it easier to begin his studies the year before; instead of sifting the earth to find the eggs from which the young insects are hatched in the spring, he ob- serves the mature insects in the fall and secures a supply of eggs freshly laid by the females, either in the field or in cages properly equipped for them. In the laboratory then
Fic. 1. Young grasshoppers
he can closely watch the hatching and observe with ac- curacy the details of the emergence. So, let us reverse the calendar and take note of what the mature grasshoppers of last season’s crop are doing in August and September. First, however, it is necessary to know just what insect is a grasshopper, or what insect we designate by the name; for, unfortunately, names do not always signify the same thing in different countries, nor is the same name always applied to the same thing in different parts of the same country. It happens to be thus with the term “grass- hopper.” In most other countries they call grasshoppers “locusts,” or rather, the truth is that we in the United States call locusts “grasshoppers,” for we must, of course, concede priority to Old World usage. When you read of a “plague of locusts,” therefore, you must understand “grasshoppers.” But a swarm of “‘seventeen-year locusts” means quite another insect, neither locust nor grasshopper —correctly, a cicada. All this mix-up of names and many other misfits in our popular natural history parlance we
[2]
THE GRASSHOPPER
can blame probably on the early settlers of our States, who bestowed upon the creatures encountered in the New World the names of animals familiar at home; but, having no zoologists along for their guidance, they made many errors of identification. Scientists have sought to estab- lish a better state of nomenclatural affairs by creating a set of international names for all living things, but since their names are in Latin, or Latinized Greek, they are seldom practicable for everyday purposes. Knowing now that a grasshopper is a locust, it only needs to be said that a true locust is any grasshopperlike insect with short horns, or antennae (see Fron- tispiece). A similar in- sect with long slender antennae is either a katydid (Figs. 23, 24), or a member of the cricket family (Fig. 39). If you will collect and
Fic. 2. The end of the body of a male and
examine a few specimens a female grasshopper
of locusts, which we will The body, or abdomen, of a male (A) is 2 bluntly rounded; that of the female (B)
proceed to call grass- bears two pairs of thick prongs, which
hoppers, you may ob- constitute the egg-laying organ, or ovi-
positor (Oup) serve that some have
the rear end of the body smoothly rounded and that others have the body ending in four horny prongs. The second kind are females (Fig. 2 B); the others (A) are males and may be disregarded for the present. It is one of the pro- visions of nature that whatever any creature is compelled by its instinct to do, for the doing of that thing it is pro- vided with appropriate tools. Its tools, however, unless
[3]
INSECGES
it is a human animal, are always parts of its body, or of its jaws or its legs. The set of prongs at the end of the body of the female grasshopper constitutes a digging tool, an instrument by means of which the insect makes a hole in the ground wherein she deposits her eggs. Entomologists call the organ an ovipositor, or egg-placer. Figure 2 B
Fic. 3. A female grasshopper in the position of depositing a pod of eggs in a hole in the ground dug with her ovipositor. (Drawn from a photograph in U.S. Bur. Ent.)
shows the general form of a grasshopper’s ovipositor; the prongs are short and thick, the points of the upper pair are curved upward, those of the lower bent downward. When the female grasshopper is ready to deposit a batch of eggs, she selects a suitable spot, which is almost any place in an open sunny field where her ovipositor can penetrate the soil, and there she inserts the tip of her organ with the prongs tightly closed. When the latter are well within the ground, they are probably spread apart so as to compress the earth outward, for the drilling
4]
THE GRASSHOPPER
process brings no detritus to the surface, and gradually the end of the insect’s body sinks deeper and deeper, until a considerable length of it is buried in the ground (Fig. 3). Now all is ready for the discharge of the eggs. The exit duct from the tubes of the ovary, which are filled with eggs already ripe, opens just below and between the bases of the lower prongs of the ovipositor, so that, when the upper and lower prongs are separated, the eggs escape from the passage between them. While the eggs are being placed in the bottom of the well, a frothy gluelike substance from the body of the insect is discharged over them. This sub- stance hardens about the eggs as it dries, but not in a solid mass, for its frothy nature leaves it full of cavities, like a sponge, and affords the eggs, and the young grasshoppers when they hatch, an abundance of space for air. To the outside of the covering substance, while it 1s fresh and sticky, particles of Fr Fes pods‘of = euasshopper, show earth adhere and make a "the egas within. (Much enlarged) finely granular coating over the mass, which, when hardened, looks like a small pod or capsule that has been molded into the shape of the cavity containing it (Fig. 4). The number of eggs within each pod varies greatly, some pods coritaining only half a dozen eggs, and others as many as one hundred and fifty. Each female also deposits several batches of eggs, each lot in a separate burrow and pod, before her egg supply is exhausted. Some species arrange the eggs regularly in the pods, while others cram them in hap- hazard.
[5]
INSECTS
The egg of a grasshopper is elongate-oval in shape (Fig. 5), those of ordinary-sized grasshoppers being about three-sixteenths of an inch in length, or a little longer. The ends of the eggs are rounded or bbhamn tly pointed, and the lower extremity (the egg being generally placed on end) appears to have a small cap over it. One side of the egg is always more curved than the
opposite side, Fic. 5. Eggs of a grasshopper; one split at the upper ven i il end, showing the young grasshopper about to emerge which may be al-
most straight. The surface is smooth and lustrous to the naked eye, but under the microscope it 1s seen to be marked off by slightly raised lines into many small polygonal areas.
Within each egg is the germ that is to produce a new grasshopper. This germ, the living matter of the egg, is but a minute fraction of the entire egg contents, for the bulk of the latter consists of a nutrient substance, called yolk, the purpose of which is to nourish the embryo as it develops. The tiny germ contains in some form, that even the strongest microscope will not reveal, the properties which will determine every detail of structure in the future grasshopper, except such as may be caused by external cir- cumstances. It would be highly interesting to follow the course of the development of the embryo insect within the egg, and most of the important facts about it are known; but the story would be entirely too long to be given here, though a few things about the grasshopper’s development should be noted.
[6]
THE GRASSHOPPER
The egg germ begins its development as soon as the eggs are laid in the fall. In temperate or northern latitudes, however, low temperatures soon intervene, and develop- ment is thereby checked until the return of warmth in the spring—or until some entomologist takes the eggs into an artificially heated laboratory. The eggs of some species of grasshoppers, if brought indoors before the advent of freezing weather and kept in a warm place, will proceed with their development, and young grasshoppers will emerge from them in about six weeks. On the other hand, the eggs of certain species, when thus treated, will not hatch at all; the embryos within them reach a certain stage of development and there they stop, and most of them never will resume their growth unless they are sub- jected to a freezing temperature! But, after a thorough chilling, the young grasshoppers will come out, even in January, if the eggs are then transferred to a warm place.
To refuse to complete its development until frozen and then warmed seems like a preposterous bit of inconsistency on the part of an insect embryo; but the embryos of many kinds of insects besides the grasshopper have this same habit from which they will not depart, and so we must con- clude that it is not a whim but a useful physiological prop- erty with which they are endowed. The special deity of nature delegated to look after living creatures knows well that Boreas sometimes oversleeps and that an egg laid in the fall, if it depended entirely on warmth for its develop- ment, might hatch that same season if mild weather should continue. And then, what chance would the poor fledgling have when a delayed winter comes upon it? None at all, of course, and the whole scheme for perpetuation of the species would be upset. But, if it is so arranged.that development within the egg can reach completion only after the chilling effect of freezing weather, the emergence of the young insect will be deferred until the return of warmth in the spring, and thus the species will have a guarantee that its members will not be cut down by unsea-
lira
INSECTS
sonable hatching. There are, however, species not thus in- sured, and these do suffer losses from fall hatching every time winter makes a late arrival. Eggs laid in the spring are designed to hatch the same season, and the eggs of species that live in warm climates never require freezing for their development.
The tough shell of the grasshopper’s egg is composed of two distinct coats, an outer, thicker, opaque one of a pale brown color, and an inner one which is thin and transparent. Just before hatch- ing, the outer coat splits open in an ir- regular break over the upper end of the egg, and usually half or two-thirds of the way down the flat side. This outer coat can easily be removed artificially, and the inner coat then appears as a glisten- ing capsule, through the semitransparent walls of which the little grasshopper in- side can be seen, its members all tightly folded beneath its body. When the hatching takes place normally, however, both layers of the eggshell are split, and ae eee the young grasshopper emerges by slowly
its eggshell making its way out of the cleft (Fig. 6).
Newly-hatched grasshoppers that have come out of eggs which some meddlesome investigator has removed from their pods for observation very soon proceed to shed an outer skin from their bodies. This skin, which is already loosened at the time of hatching, appears now as a rather tightly fitting garment that cramps the soft legs and feet of the delicate creature within it. The latter, however, after a few forward heaves of the body, accompanied by expansions of two swellings on the back of the neck (Fig. 6), succeeds in splitting the skin over the neck and the back of the head, and the pellicle then rapidly shrinks and slides down over the body. The insect, thus first exposed,
[8]
THE GRASSHOPPER
liberates itself from the shriveled remnant of its hatching skin, and becomes a free new creature in the world. Being a grasshopper, it proceeds to jump, and with its first ef- forts clears a distance of four or five inches, something like fifteen or twenty times the length of its own body.
When the young locusts hatch under normal undisturbed conditions, however, we must picture them as coming out of the eggs into the cavernous spaces of the egg pod, and all buried in the earth. They are by no means yet free creatures, and they can gain their liberty only by burrow- ing upward until they come out at the surface of the ground. Of course, they are not very far beneath the sur- face, and most of the way will be through the easily pene- trated walls of the cells of the egg covering. But above the latter is a thin layer of soil which may be hard-packed after the winter’s rains, and breaking through this layer can not ordinarily be an easy task. Not many entomolo- gists have closely watched the newly-hatched grasshopper emerge from the earth, but Fabre has studied them under artificial conditions, covered with soil in a glass tube. He tells of the arduous efforts the tiny creatures make, press- ing their delicate bodies upward through the earth by means of their straightened hind legs, while the vesicles on the back of the neck alternately contract and expand to widen the passage above. All this, Fabre says, is done before the hatching skin 1s shed, and it is only after the surface is reached and the insect has attained the freedom of the upper world that the inclosing membrane is cast off and the limbs are unencumbered.
The things that insects do and the ways in which they do them are always interesting as mere facts, but how much wiser might we be if we could discover why they do them! Consider the young locust buried in the earth, for example, scarcely yet more than an embryo. How does it know that it is not destined to live here in this dark cavity in which it first finds itself? What force activates the mech- anism that propels it through the earth? And finally,
Lg]
INSECTS
what tells the creature that liberty is to be found above, and not horizontally or downward? Many people believe that these questions are not to be answered by human knowledge, but the scientist has faith in the ultimate solu- tion of all problems, at least in terms of the elemental forces that control the activities of the universe.
We know that all the activities of animals depend upon the nervous system, within which a form of energy resides that is delicately responsive to external influences. Any kind of energy harnessed to a physical mechanism will produce results depending on the con- struction of the mechanism. So the ef- fects of the nerve force within a living animal are determined by the physical structure of the animal. An instinctive action, then, is the expression of nerve energy working in a particular kind of machine. It would involve a digression too long to explain here the modern con- ception of the nature of instinct; it is SX sufficient to say that something in the
surroundings encountered by the newly-
PA aes hatched grasshopper, or some substance
generated within it, sets its nerve energy into action, that the nerve energy work- ing on a definite mechanism produces the motions of the insect, and that the
Fic. 7. Eggs of a species of katydid at- tached to a twig; the young insect in suc- cessive stages of emerg- ing from an egg; and the newly-hatched young
mechanism is of such a nature that it works against the pull of gravity. Hence the creature, if normal and healthy in all respects, and if the obstacles are not too great, arrives at the surface of the ground as inevitably as a submerged cork comes to the surface of the water. Some
readers will object that an idea like this destroys the romance of life, but whoever wants romance must go to the fiction writers; and even romance is not good fiction
[10]
THE GRASSHOPPER
unless it represents an effort to portray some truth. Insects hatched from eggs laid in the open may begin life under conditions a little easier than those imposed upon the young grasshopper. Here, for example (Fig. 7), are some eggs of insects belonging to the katydid family. They look like flat oval seeds stuck in overlapping rows, some on a twig, others along the edge of a leaf. When about to hatch, each egg splits halfway down one edge and crosswise on the exposed flat surface, allowing a flap to open on this side, which gives an easy exit to the young insect about toemerge. The latter is inclosed in a delicate transparent sheath, within which its long legs and an- tennae are closely doubled up beneath the body; but when the egg breaks open, the sheath splits also, and as the young insect emerges it sheds the skin and leaves it within the shell. The new creature has nothing to do now but to stretch its long legs, upon which it walks away, and, if given suitable food, it will soon be contentedly feeding. Let us now take closer notice of the little grasshoppers (Fig. 8) that have just come into the great world from the dark subterranean chambers of their egg-pods. Such an inordinately large head surely, you would say, must over- balance the short tapering body, though supported on three pairs of legs. But, whatever the proportions, nature’s works never have the appearance of being out of drawing; because of some law of recompense, they never give you the uneasy feeling of an error in construction. In spite of its enormous head, the grasshopper infant is an agile crea- ture. Its six legs are all attached to the part of the body immediately behind the head, which is known as the thorax (Fig. 63, Th), and the rest of the body, called the abdomen (Ab), projects free without support. An insect, according to its name, is a creature divided into parts, for “insect” means “‘in-cut.’’ A fly or a wasp, therefore, comes closer to being the ideal insect; but, while not literally in- sected between the thorax and abdomen, the grasshopper, like the fly and the wasp and all other insects, consists of a
Parl
INSECTS
head, a thorax bearing the legs, and a terminal abdomen (Fig. 63). On the head is located a pair of long, slender antennae (Ant) and a pair of large eyes (E). Winged in- sects have usually two pairs of wings attached to the back of the thorax (W2, W3).
The outside of the insect’s body, instead of presenting a continuous surface like that of most animals, shows many encircling rings where the hard integument appears to be infolded, as it really is, dividing each body region except the head into a series of short overlapping sections. These body sections are called segments, and all insects and their relatives, in- cluding the centipedes,
the shrimps, lobsters, and = crabs, and the scorpions and spiders, are seg- mented animals. The in- sect’s thorax consists of three segments, the first of which carries the first pair of legs, the second the middle pair of legs, and the third the hind pair of legs. The abdomen usually consists of ten or eleven segments, but generally has no appendages, except a pair of small peglike organs at the end known as the cerci, and, in the adult female, the prongs of the ovipositor (Fig. 2 B), which belong to the eighth and ninth segments.
The head, besides carrying the antennae (Fig. 63, 41), has three pairs of appendages grouped about the mouth, which serve as feeding organs and are known collectively as the mouth parts. The presence of four pairs of append- ages on the head raises the question, then, as to why the head is not segmented like the thorax and the abdomen. At an early stage of embryonic growth the head 7s seg- mented, and each pair of its appendages is borne by a single segment, but the head segments are later condensed
[12]
Fic. 8. A young grasshopper, or nymph, in the second stage after hatching
THE GRASSHOPPER
into the solid capsule of the cranium. Thus we see that the entire body of an insect is composed of a series of seg- ments which have become grouped into the three body regions. Note that the insect does not have a “nose” or any breathing apertures on its head. It has, however, many nostrils, called spiracles (Fig. 70, Sp), distributed along each side of the thorax and the abdomen. Its breathing ~ system is quite different from ours, but will wag be described in another chapter treating of the internal organization (page 114). Most young insects grow rapidly be- cause they must compress their entire lives within the limits of a single season. Generally a few weeks suffice for them to reach maturity, or at least the ma- ture growth of the form in which they leave the egg, for, as we shall see, many in- sects complicate their lives by having several different stages, in each of which they present quite a dif- ferent form. The grass- hopper, however, is an in- sect that grows by a direct course from its form at hatch- ing to that of the adult, and at all stages it Is recog- nizable as a grass- hopper (Fig. 9). A
young moth, on Fic. 9. The metamorphosis of a grasshopper, Melanoplus atlanus, showing its six stages of develop-
the other hand, ment from the newly-hatched nymph to the fully-
hatching In the winged adult. (Twice natural size)
Pea
INSEGES
form of a caterpillar, has no resemblance to its parent, and the same is true of a young fly, which is a maggot, and of the grublike young of a bee. The changes of form that insects undergo during their growth are known as meta- morphosis. There are different degrees of such trans- formation; the grasshopper and its relatives have a simple metamorphosis.
An insect differs from a vertebrate animal in that its muscles are attached to its skin. Most species of insects have the skin hardened by the formation of a strong out- side cuticula to give a firm support to the muscles and to resist their pull. This function of the cuticula, however, imposes a condition of permanency on it after it is once formed. As a consequence the growing insect is con- fronted with the alternatives, after reaching a certain size, of being cramped to death within its own skin, or of discarding the old covering and getting a new and larger one. It has adopted the course of expediency, and peri- odically mo/ts. Thus it comes about that the life of an insect progresses by stages separated by the molts, or the shedding of the cuticula.
The grasshopper makes six molts between the time of hatching and its attainment of the final adult form, a period of about six weeks, and goes through six post- embryonic stages (Fig. 9). The first molt is the shedding of the embryonic skin, which, we have seen, takes place normally as soon as the young insect emerges from the earth. The grasshopper now lives uneventfully for about a week, feeding by preference on young clover leaves, but taking almost any green thing at hand. During this time its abdomen lengthens by the extension of the membranes between its segments, but the hard parts of the body do not change either in size or in shape. At the end of seven or eight days, the insect ceases its activities and remains quiet for a while until the cuticula opens in a lengthwise split over the back of the thorax and on the top of the head. ‘The dead skin is then cast off, or rather, the grass-
[14]
THE GRASSHOPPER
hopper emerges from it, carefully pulling its legs and an- tennae from their containing sheaths. The whole process consumes only a few minutes. The emerged grasshopper is now entering its third stage after hatching, but the shed- ding of the hatching skin is usually not counted in the series of molts, and the first subsequent molt, then, we will say, ushers it into its second stage of aboveground life. In this state the insect is different in some respects from what it was in the first stage: it is not only larger, but the body is longer in proportion to the size of the head, as are also the antennae, and particularly the hind legs. Again the insect becomes active and pursues its routine life for another week; then it undergoes a second molting, ac- companied by changes in form and proportions that make it a little more like a mature grasshopper. After shedding its cuticula on three succeeding occasions, it appears in the adult form, which it will retain throughout the remainder of its life.
The grasshopper developed its legs, its antennae, and most of its other organs while it was in the egg. It was hatched, however, without wings, and yet, as everyone knows, most full-grown grasshoppers have two pairs of wings (Fig. 63, W2, W;), one pair attached to the back of the middle segment of the thorax, the other to the third segment. It has acquired its wings, therefore, during its growth from youth to maturity, and by examining the insect in its different stages (Fig. 9), we may learn some- thing of how the wings are developed. In the first stage, evidence of the coming wings is scarcely apparent, but in the second, the lower hind angles of the plates covering the back of the second and third thoracic segments are a little enlarged and project very slightly as a pair of lobes. In the third stage, the lobes have increased in size and may now be suspected of being rudiments of the wings, which, indeed, they are. At the next molt, when the insect enters its fourth stage, the little wing pads are turned upward and laid over the back, which disposition not only
Nera |
INSECTS
reverses the natural position of the wings, but brings the hind pair outside the front pair. At the next molt, the wings retain their reversed positions, but they are once more increased in size, though they still remain far short of the dimensions of the wings of an adult grasshopper.
At the time of the last molt, the grasshopper takes a position with its head downward on some stem or twig, which it grasps securely with the claws of its feet. Then, when its cuticula splits, it crawls downward out of the skin. Once free, however, it reverses its position, and the wisdom of this act is seen on observing the rapidly expand- ing and lengthening wings, which can now hang down- ward and spread out freely without danger of crumpling. In a quarter of an hour the wings have enlarged from small, insignificant pads to long, thin, membranous fans eat reach to the tip of the body. This rapid growth 1s ex- plained by the fact that the wings are hollow sacs; their visible increase in size is a mere distention of their wrinkled walls, for they were fully formed beneath the old cuticula and lay there before the molt as little crumpled wads, which, when released by the removal of the cases that cramped them, rapidly spread out to their full dimensions. Their thin, soft walls then come together, dry, and harden, and the limp, flabby bags are converted into organs of flight.
It isimportant to understand the process of molting as it takes place in the grasshopper, because the processes of metamorphosis, such as those which accomplish the trans- formation of a caterpillar into a butterfly, differ only in degree from those that accompany the shedding of the skin between any two stages of the grasshopper’s life. The principal growth of the insect 1s made during those resting periods preceding the molts. It is then that the various parts enlarge and make whatever alterations in shape they are to have. The old cuticula is already loosened and the changes go on beneath it, while at the same time a new cuticula is generated over the remodeled surfaces. The
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THE GRASSHOPPER
increased size of the antennae, legs, and wings causes them to be compressed in the narrow space between the new and the old cuticula, and, when the latter is cast off, the crumpled appendages expand to their full size. The ob- server then gets the 1 impression that he is witnessing a sud- den transformation. The impression, however, is a false one; what is really going on is comparable with the display of new dresses and coats that the merchant puts into his show windows at the proper season for their use, which he has just unpacked from their cases but which were pro- duced in the factories long before.
The adult grasshoppers lead prosaic lives, but, like a great many good people, they fill the places allotted to them in the world, and see to it that there will be other occupants of their own kind for these same places when they themselves are forced to vacate. If they seldom fly high, it is because it 1s not the nature of locusts to do so; and if, in the East, one does sometimes soar above his fellows, he accomplishes nothing, unless he happens to land on the upper regions of a Manhattan skyscraper, when he may attain the glory of a newspaper mention of his exploit—most likely, though, with his name spelled wrong.
On the other hand, like all common folk born to ob- scurity and enduring impotency as individuals, the grass- hopper in masses of his kind becomes a formidable creature. Plagues of locusts are of historic renown in countries south of the Mediterranean, and even in our own country hordes of grasshoppers known as the Rocky Mountain locust did such damage at one time in the States of the Middle West that the government sent out a commission of entomolo- gists to investigate them. This was in the years following the Civil War, when, for some reason, the locusts that normally inhabited the Northwest, east of the Rocky Mountains, became dissatisfied with their usual breeding grounds and migrated in great swarms into the States of the Mississippi valley, where they brought destruction to
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INSECTS
all kinds of crops wherever they chanced to alight. In the new localities they would lay their eggs, and the young of the next season, after acquiring their wings, would migrate back toward the- ‘region whence the parent swarm had come the year before.
The entomologists of the investigating commission in the year 1877 tell us that on a favorable day the migrating locusts “rise early in the forenoon, from eight to ten o'clock, and settle down to eat from four to five in the afternoon. The rate at which they travel is variously estimated from three to fifteen or twenty miles an hour, determined by the velocity of the wind. Thus, insects which began to fly in Montana by the middle of July may not reach Missouri until August or early September, a period of about six weeks elapsing before they reach their destined breeding grounds.” The appearance of a swarm in the air was described as being like that of “‘a vast body of fleecy clouds,’ ” or a “cloud of snowflakes,” the mass of flying insects “often having a depth that reaches from comparatively near the ground to a height that baffles the keenest eye to distinguish the insects in the upper stratum.” It was estimated that the locusts could fly at an elevation of two and a half miles from the general surface of the ground, or 15,000 feet above sea level. The descending swarm falls upon the country “like a plague or a blight,” said one of the entomologists of the com- mission, Dr. C. V. Riley, who has left us the following
graphic picture of the circumstances:
The farmer plows and plants. He cultivates in hope, watching his growing grain in graceful, wave-like motion wafted to and fro by the warm summer winds. The green begins to golden; the harvest is at hand. Joy lightens his labor as the fruit of past toil is about to be realized. The day breaks with a smiling sun that sends his ripening rays through laden orchards and: promising fields. Kine and stock of every sort are sleek with plenty, and all the earth seems glad. The day grows. Suddenly the sun’s‘face is darkened, and clouds obscure the sky. The joy of the morn gives way to ominous fear. The day closes, and ravenous locust-swarms have fallen upon the land. The
[18]
THE GRASSHOPPER
morrow comes, and, ah! what a change it brings! The fertile land of promise and plenty has become a desolate waste, and old Sol, even at his brightest, shines sadly through an atmosphere alive with myriads of glittering insects.
Even today the farmers of the Middle Western States are often hard put to it to harvest crops, especially alfalfa and grasses, from fields that are teeming with hungry grasshoppers. By two means, principally, they seek relief from the devouring hordes. One method 1s that of driv- ing across the fields a device known as a “‘hopperdozer,’ which collects the insects bodily and destroys them. The dozer consists essentially of a long shallow pan, twelve or fifteen feet in length, set on low runners and provided with a high back made either of metal or of cloth stretched over a wooden frame. The pan contains water with a thin film of kerosene over it. As the dozer is driven over the field, great numbers of the grasshoppers that fly up before it either land directly in the pan or fall into it after striking the back, and the kerosene film on the water does the rest, for kerosene even in very small quantity is fatal to the insects. In this manner, many bushels of dead locusts are taken often from each acre of an alfalfa field; but still great numbers of them escape, and the dozer naturally can not be used on rough or uneven ground, in pastures, or in fields with standing crops. A more generally effec- tive method of killing the pests is that of poisoning them. A mixture 1s prepared of bran, arsenic, cheap molasses, and water, sufficiently moist to adhere in small lumps, with usually some substance added which is supposed to make the “mash” more attractive to the insects. The deadly bait is then finely broadcast over the infested fields.
While such methods of destruction are effective, they bear the crude and commonplace stamp of human ways. See how the thing is done when insect contends against insect. A fly, not an ordinary fly, but one known to entomologists as Sarcophaga kellyi (Fig. 10), being named after Dr. KF. O. G. Kelly, who has given us a
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INSECTS
description of its habits, frequents the fields in Kansas where grasshoppers are abundant. Individuals of this fly, according to Doctor Kelly’s account, are often seen to dart after grass- hoppers on the wing and _ strike against them. The stricken in- sect at once drops to the ground. Examination re- veals no physical injury to the vic- tim, but on a close inspection there Fic. 10. A fly whose larvae are parasitic on grass- may be found ad- hoppers, Sarcophaga kellyi. (Much enlarged) hering to the un- der surface of a wing several tiny, soft, white bodies. Poison pills? Pellets of infection? Nothing so ordinary. The things are alive, they creep along the folds of the wing toward its base—they are, in short, young flies born at the instant the body of the mother fly struck the wing of the grass- hopper. But a young fly would never be recognized as the offspring of its parent; it is a wormlike creature, or maggot, having neither wings nor legs and capable of moving only by extending and contracting its soft, flexible body ae 182 D).
In form, the young Sarcophaga kellyi does not differ par- ticularly from the maggots of other kinds of flies, but the Sarcophaga flies in general differ from most other insects in that their eggs are hatched within the bodies of the females, and these flies, therefore, give birth to young maggots instead of laying eggs. The female of Sarcophaga kellyi, then, when she launches her attack on the flying grasshopper, is munitioned with a load of young maggots ready to be discharged and stuck by the moisture of their
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THE GRASSHOPPER
bodies to the object of contact. The young parasites thus palmed off by their mother on the grasshopper, who has no idea what has happened to him, make their way to the base of the wing of their unwitting host, where they find a ten- der membranous area which they penetrate and thereby enter the body of the victim. Here they feed upon the liquids or tissues of the now helpless insect and grow to maturity in from ten to thirty days. Meanwhile, how- ever, the grasshopper has died; and when the parasites are full grown, they leave the dead body and bury themselves in the earth to a depth of from two to six inches. Here they undergo the transformation that will give them the form of their parents, and when they attain this stage they issue from the earth as adult winged flies. Thus, one insect 1s destroyed that another may live.
Is the Sarcophaga kellyi a creature of uncanny shrewd- ness, an ingenious 1 inventor of a novel way for avoiding the work of caring for her offspring? Certainly her method is an improvement on that of leaving one’s newborn prog- eny on a stranger’s doorstep, for the victim of the fly must accept the responsibility thrust upon him whether he will or not. But Doctor Kelly tells us that the flies do not know grasshoppers from other flying insects, such as moths and butterflies, in which their maggots do not find congenial hosts and never reach maturity. Furthermore, he says, the ardent fly mothers will go after pieces oF crumpled paper thrown into the wind and will discharge their maggots upon them, towhich the helpless infants cling without hope of survival. Such performances, and many similar ones that could be recounted of other insects, show that instinct is indeed blind and depends, not upon fore- sight, but on some mechanical action of the nervous sys- tem, which gives the desired result in the majority of cases but which is not guarded against unusual conditions or emergencies.
When we consider the many perfected instincts among insects, we are often shocked to find apparent cases of
Lan |
INSECTS
flagrant neglect on the part of nature for her creatures, where it would seem a remedy for their ills would be easy to supply.
In human society of modern times the criminal ‘element has come to look no different from the law-abiding class of citizens. Formerly, if we may judge from pictures and stage representations, thieves and thugs were tough-look- ing individuals that could not be mistaken on sight, but
Fic. 11. Two blister beetles whose larvae feed on grasshopper eggs. (Twice natural size)
A, Epicauta marginata. B, Epicauta vittata
today our bandits are spruce young fellows that pass with- out suspicion in the crowd. And thus it is with the in- sects, all unsuspectingly one may be rubbing elbows with another that overnight will despoil his home, or that has already committed some act of violence against his neigh- bor. Here, for example e, in the same field with the grass- hoppers, is an innocent-looking beetle, about three- quarters of an inch in length, black and striped with yellow (Fig. 11 B). His entomological name is Epicauta vittata, which, of course, means nothing to a locust. He is now a vegetarian, but in his younger days he ravished the nest of a grasshopper and devoured the eggs, and his progeny will do the same again. Epicauta and others of his family
Pee)
THE GRASSHOPPER
are known as “blister beetles’? because they have a sub- stance in their blood, called cantharidin, famous for its blistering properties and formerly much used in medicine. The female blister beetles of several species lay their eggs in the ground in regions frequented by grasshoppers, where the young on hatching can find the egg-pods of the latter. The little beetles (Fig. 12) hatch in a form quite different from that of their parents and are known as /riungulins because of two spines beside the single claw on each of their feet, which gives the foot a three-clawed appearance. Though the young scapegrace of a beetle is a housebreaker and a thief, his story, like that of too many criminals, unfortunately, makes interesting read-
ing, and the following account is taken, ¥ with a few omissions, from the history ; of Epicauta vittata as given by Dr. CoV Riley:
Ss
oe
From July till the middle of October the eggs are being laid in the ground in loose, irreg- ular masses of about 130 on an average—the female excavating a hole for the purpose, and afterwards covering up the mass by scratching
with her feet. She lays at several different =I intervals, producing in the aggregate probably from four to five hundred ova. She prefers for R
purposes of oviposition the very same warm sunny locations chosen by the locusts, and doubtless instinctively places her eggs near those of these last, as I have on several occa- Fic. 12. The _ first- sions found them in close proximity. In the — stage Jarva, or “triun- course of about 10 days—more or less, accord- ae ote, coped 3 ; : ister beetle (fig. 11 ing to the temperature of the ground—the g). Enlarged 12 times first larva or triungulin hatches. These little (From Riley) triungulins (Fig. 12), at first feeble and per-
fectly white, soon assume their natural light-brown color and commence to move about. At night, or during cold or wet weather, all those of a batch huddle together with little motion, but when warmed by the sun they become very active, running with their long legs over the ground, and prying with their large heads and strong jaws into every crease and crevice in the soil, into which, in due time, they burrow
[231]
\
INSECTS
and hide. As becomes a carnivorous creature whose prey must be industriously sought, they display great powers of endurance, and will survive for a fortnight without food in a moderate temperature. Yet in the search for locust eggs many are, without doubt, doomed to perish, and only the more fortunate succeed in finding appropriate diet.
Reaching a locust egg-pod, our triungulin, by chance, or instinct, or both combined, commences to burrow through the mucous neck, or covering, and makes its first repast thereon. If it has been long in search, and its jaws are well hardened, it makes quick work through this porous and cellular matter, and at once gnaws away at an egg, first devouring a portion of the shell, and then, in the course of two or three days, sucking up the contents. Should two or more triun- gulins enter the same egg-pod, a deadly conflict sooner or later ensues until one alone remains the victorious possessor.
The surviving triungulin then attacks a second egg and more or less completely exhausts its contents, when, after about eight days from the time of its hatching, it ceases from its feeding and enters a period of rest. Soon the skin splits along the back, and the creature issues in the second stage of its existence. Very curiously, it 1s now quite different in appearance, being white and soft-bodied and having much shorter legs than before (Fig. 13). After feeding again on the eggs for about a week, the creature molts a second time and appears in a still different form. Then once more, and yet a fourth time, it sheds its skin and changes its form. Just before the Fic. 13. The second. fourth molt, however, it quits the eggs stage larva of the and burrows a short distance into the Pee ye soil, where it composes itself for a
period of retirement, and here undergoes another molt, in which the skin is not cast of. Thus the half-grown insect passes the winter, and in spring molts a sixth time and becomes active again, but not for long—its larval life is now about to close, and with another molt
| 24 ]
THE GRASSHOPPER
it changes to a pupa, the stage in which it is to be trans- formed back into the form of its beetle parents. The final change is accomplished in less than a week, and the creature then emerges from the soil, now a fully-formed striped blister beetle.
The grasshoppers’ eggs furnish food for many other insects besides the young blister beetles. There are species of flies and of small wasplike insects whose larvae feed in the egg-pods in much the same manner as do the triungu- lins, and there are still other species of general feeders that devour the locust eggs as a part of their miscellaneous diet. Notwithstanding all this destruction of the germs of their future progeny, however, the grasshoppers still thrive in abundance, for grasshoppers, like most other insects, put their trust in the admonition that there is safety innumbers. So many eggs are produced and stored away in the ground each season that the whole force of their enemies combined can not destroy them all, and enough are sure to come through intact to render certain the continuance of the species. Thus we see that nature has various ways of accomplishing her ends—she might have given the grasshopper eggs better protection in the pods, but, being usually careless of individuals, she chose to guarantee perpetuance with fertility.
[25]
CHAPTERS THE GRASSHOPPER’S COUSINS
Nature’s tendency is to produce groups rather than in- dividuals. Any animal you can think of resembles in some way another animal or a number of other animals. An insect resembles on the one hand a shrimp or a crab, and on the other a centipede or a spider. Resemblances among animals are either superficial or fundamental. For example, a whale or a porpoise resembles a fish and lives the life of a fish, but has the skeleton and other organs of land-inhabiting mammals. Therefore, notwithstanding their form and aquatic habits, whales and porpoises are classed as mammals and not as fishes.
When resemblances between animals are of a funda- mental nature, we believe that they represent actual blood relationships carried down from some far-distant common ancestor; but the determination of relationships between animals is not always an easy matter, because it is often dificult to know what are fundamental characters and what are superficial ones. It is a part of the work of zoologists, however, to investigate closely the structure of all animals and to establish their true relationships. The ideas of relationship which the zoologist deduces from his studies of the structure of animals are expressed in his classification of them. The primary divisions of the Animal Kingdom, which is generally likened to a tree, are called branches, or pAy/a (singular, phy/um).
The insects, the centipedes, the spiders, and the shrimps, crayfish, lobsters, crabs, and other such creatures belong to the phylum Arthropoda. The name of this phylum means
[ 26 ]
fHE GRASSHOPPER’S. COUSINS
“jointed-legs”’; but, since many other animals have jointed legs, the name is not distinctive, except in that the legs of the arthropods are particularly jointed, each being com- posed of a series of pieces that bend upon each other in different directions. A name, however, as everybody knows, does not have to mean anything, for Mr. Smith
lic. 14. Examples of four common classes of the Arthropoda
A,a crab (Crustacea). B,a spider (Arachnida). C, a centipede (Chilopoda).
D, a fly (Insecta, or Hexapoda) may be a carpenter, and Mr. Carpenter a smith. A phylum is divided into classes, a class into orders, an order into families, a family into genera (singular, genus), and a genus is composed of species (the singular of which is also species). Species are hard to define, but they are what we ordinarily regard as the individual kinds of animals. Species are given double names, first the genus name, and second a specific name. For example, species of a common grass- hopper genus named Me/anoplus are distinguished as Melanoplus atlanus, Melanoplus femur-rubrum, Melanoplus differentialis, etc.
[ 27 ]
INSECTS
The insects belong to the class of the Arthropoda known as the Insecta, or Hexapoda. The word “insect,” as we have seen, means “‘in-cut,” while ‘“‘hexapod” means “‘six- legged” —either term, then, doing very well for insects. The centipedes (Fig. 14 C) are the Myriapoda, or many- footed arthropods; the crabs (A), shrimps, lobsters, and others of their kind are the Crustacea, so called because most of them have hard shells; the spiders (B) are the Arachnida, named after that ancient Greek maiden so boastful of her spinning that Minerva turned her into a spider; but some arachnids, such as the scorpion, do not make webs.
The principal groups of insects are the orders. The grasshopper and its relatives constitute an order; the beetles are an order; the moths and butterflies are another order; the flies another; the wasps, bees, and ants still another. The grasshopper’ s order 1 is called the Orthoptera, the word meaning “‘straight- wings,’ * but, again, not sig- nificant in all cases, though serving very well as a name. The order is a group of related families, and, in the Or- thoptera, the grasshoppers, or locusts, make one family, the katydids another, the crickets a third; and all these 1n- sects, together with some others less familiar, may be said to be the grasshopper’s cousins.
The orthopteran families are notable in many ways, some for the great size attained by their members, some for their remarkable forms, and some for musical talent. While this chapter will be devoted principally to the cousins of the grasshopper, a few things of interest may still be said about the grasshopper himself, in addition to what was given in the preceding chapter.
THe GRASSHOPPER FAMILY
The family of the grasshoppers, or locusts, is the Acrididae. All the members are much alike in form and habits, though some have long wings and some short wings, and some reach the enormous size of nearly six inches in
[ 28 ]
READE, t
A group of insects representing five common entomological Orders.
Figure 2 is a damselfly, a kind of dragonfly, from New Guinea, Order Odonata; 4 is a grasshopper, and 6 a winged walking-stick of Japan, representing two families of Orthoptera; 1 and 8 are sucking bugs, Order Hemiptera, which includes also the aphids and the cicadas; 3 is a wasp from Paraguay, and 7 a solitary bee from Chile, Order Hymenoptera; 5 is a two-winged fly of the Order Diptera, from Japan. To entomologists these insects are known as follows: 1, Paryphes laetus; 2, unidentified; 3, Pepsis completa; 4, Heliastus benjamini; 5, Pantophthalmus vittatus; 6, Micadina phluctanotdes; 7, Caupolicana fulvicollis; 8, Margasus afzeli
THE GRASSHOPPER’S COUSINS
length. The front wings are long and narrow (Fig. 63, W.), somewhat stiff, and of a leathery texture. They are laid over the thinner hind wings as a protection to the latter when the wings are folded over the back, and for this reason they are called the tegmina (singular, fegmen). The hind wings, when spread (V3), are seen to be large fans, each with many ribs, or veins, springing from the base. These wings are gliders rather than organs of flight. For most grasshoppers leap into the air by means of their strong hind legs and then sail off on the outspread wings as far as a weak fluttering of the latter will carry them. One of our common species, however, the Carolina locust (Frontispiece), is a strong flyer, and when
Fic. 15. A grasshopper, CAloealtis conspersa, that makes a sound by scraping its hind thighs over sharp-edged veins of its wings
A, the male grasshopper, showing the sound-making veins of the wing (4). B, inner surface of right hind leg, showing row of teeth (a) on the femur. C, several teeth of the femur (enlarged)
flushed flits away on an undulating course over the weeds and bushes and sometimes over the tops of small trees, but always swerving this way and that as if unde- cided where to alight. The great flights of the migratory locusts, described in the last chapter, are said to have been accomplished more by the winds than by the insects’ strength of wing.
The locusts are distinguished by the possession of large
[ 2g ]
INSECTS
organs on the sides of the body that appear to be designed for purposes of hearing. No insect, of course, has “ears” on its head; the grasshopper’s supposed hearing organs are located on the base of the abdomen, one on each side (Fig. 63, Tm). Each consists of an oval depression of the body wall with a thin eardrumlike membrane, or tympa- num, stretched over it. Air sacs lie against the inner face of the membrane, furnishing the equilibrium of air pressure necessary for free vibration in response to sound waves, and a complicated sensory apparatus is attached to its inner wall. Even with such large ears, however, attempts at making the grasshopper hear are never very successful; but its tympanal organs have the same structure as those of insects noted for their singing, which presumably, therefore, can hear their own sound productions.
Not many of the grasshoppers are muscial. They are mostly sedate creatures that conceal their sentiments, if they have any. They are awake in the daytime and they sleep at night—commendable traits, but habits that seldom beget much in the way of artistic attainment. Yet a few of the grasshoppers make sounds that are perhaps music in their own ears. One such is an unpretentious little brown species (Fig. 15) about seven-eighths of an inch in length, marked by a large black spot on each side of the saddlelike shield that covers his back between the head and the wings. He has no other name than his scientific one of Chloealtis conspersa, for he is not widely known, since his music is of a very feeble sort. According to Scudder, his only notes resemble ¢sikk-tstkk-tsikk, repeated ten or twelve times in about three seconds in the sun, but at a slightly lower rate in the shade. Chloealtis is a fiddler and plays two instruments at once. The fiddles are his front wings, and the bows his hind legs. On the inner surface of each hind thigh, or femur, there is a row of minute teeth (Fig. i5 B, a), shown more magnified at C. When the thighs are rubbed over the edges of the wings, their teeth scrape on a sharp-edged vein indicated by 4. This produces the
eter
fHE-GRASSHOPPER’S ‘COUSINS
tsikk-sound just mentioned. Such notes contain little music to us, but Scudder says he has seen three males sing- ing to one female at the same time. This female. however,
SS)
Se ND ay & jesse
pS
Vib 5 a) \ Cate a M
amet eee NS ary
CLs “22 D> STE Tee se se WEL so ‘\ Cs Arp mani®5<5 5-76 Seo' y Cea NT OO /
Fic. 16. A grasshopper, Mecostethus gracilis, that makes a sound by scraping sharp ridges on the inner surfaces of its hind thighs over toothed veins of the wings A, the male grasshopper. B, left front wing; the rasping vein is the one marked J. C, a part of the rasping vein and its branches more enlarged, showing rows of teeth
was busy laying her eggs in a near-by stump, and there is no evidence given to show that even she appreciated the efforts of her serenaders.
Several other little grasshoppers fiddle after the manner of Chloealtis; but another, Mecostethus gracilis by name (Fig. 16), instead of having the rasping points on the legs, has on each fore wing one vein (B, /) and its branches pro- vided with many small teeth, shown enlarged at C, upon which it scrapes a sharp ridge situated on the inner sur- face of the hind thigh.
In another group of grasshoppers there are certain species that make a noise as they fly, a crackling sound
[31]
INSECTS
apparently produced in some way by the wings themselves. One of these, common through the Northern States, is known as the cracker locust, Circotettix verruculatus, on account of the loud snapping notes it emits. Several other members of the same genus are also cracklers, the noisiest being a western species called C. carlingianus. Scudder says he has had his attention drawn to this grass- hopper “‘by its obstreperous crackle more than a quarter of a mile away. In the arid parts of the West it has a great fondness for rocky hillsides and the hot vicinity of abrupt cliffs in the full exposure to the sun, where its clattering rattle re-echoes from the walls.”
THe Katypip FamiLy
While the grasshoppers give examples of the more primitive attempts of insects at musical production and may be compared in this respect to the more primitive of human races, the katydids show the highest development of the art attained by insects. But, just as the accom- plishments of one member of a human family may give prestige to all his relations and descendants, so the talent of one noted member of the katydid family has given notoriety to all his congeners, and his justly deserved name has come to be applied by the undiscriminating public to a whole tribe of singers of lesser or very mediocre talent whose only claim to the name of katydid is that of family relationship. In Europe the katydids are called simply the longhorn grasshoppers. In entomology the family is now the Tettigoniidae, though it had long been known as'the Locustidae.
The katydids in general are most easily distinguished from the locusts, or shorthorn grasshoppers, by the great length of their antennae, those delicate, sensitive, tapering threads projecting from the forehead. But the two fami- lies differ also in the number of joints in their feet, the grasshoppers having three (Fig. 17 A) and the katydids four (B). The grasshoppers place the entire foot on the
[32]
THE GRASSHOPPER’S COUSINS
ground, while the katydids ordinarily walk on the three basal segments only, carrying the long terminal joint elevated. The basal segments have pads on their under sides that adhere to any smooth surface such as that of a leaf, but the terminal joint bears a pair of claws used when it is necessary to grasp the edge of a support. The katydids are mostly creatures of the night and, though usually plain green in color, many of them have elegant forms. Their attitudes and general comportment suggest much more re- finement and a higher breeding than that of the heavy-bodied locusts. Though some members of the katydid A family live in the fields and are very grasshopperlike or even cricketlike in form and manners, the character- istic species are seclusive inhabitants of shrubbery or trees. These are the true aristocrats of the Orthoptera. An insect musician differs in many respects from a human musician,
3 : c : Fic. 17. Distinctive char- aside from that of being an insect in- acters in the feet of the
Seddsoraeiumane being. Uhesect ‘hee familics of singing
5 a ‘ Orthoptera artists are all instrumentalists; but 4 hind foot of a a
since the poets and other ignorant hopper. B, hind foot of a
people always speak of the “singing” “*t¥4i@-_ ©, hind foot of
of the crickets and katydids, it will be
easier to use the language of the public than to correct it, especially since we have nothing better to offer than the word stridu/ating, a \.atin derivative meaning “‘to creak.” But words do not matter if we explain what we mean by them. It must be understood, therefore, that though we speak of the “‘songs’’ of insects, insects do not have true voices in the sense that “voice” is the production of sound by the breath playing on vocal cords. All the musical instruments of insects, it is true, are parts of their bodies; but they are to be likened to fiddles or drums, since, for the
se
INSECTS
production of sound, they depend upon rasping and vibrat- ing surfaces. The rasping surfaces are usually, as in the instruments of the grasshoppers (Figs. 15, 16), parts of the legs and the wings. The sound may be intensified, as in the bedy of a stringed instrument, by special resonating
Fic. 18. The front wings, or tegmina, of a meadow grasshopper, Orchelimum laticauda, illustrating the sound-making organs typical of the katydid family A, left front wing and basal part of right wing of male, showing the four main veins: subcosta (Sc), radius (R), media (M), and cubitus (Cuz); also the enlarged basal vibrating area, or tympanum (7m), of each wing, the thick file vein (fc) on the left, and the scraper (s) on the right B, lower surface of base of left wing of male, showing the file (f) on under side of the file vein (A, fv) C, right front wing of female, which has no sound-making organs, showing simple normal venation
[ 34]
areas, sometimes on the wings, sometimes on the body. The cicadas, a group of musical insects to be described in a special chapter, have large drumheads in the wall of the body with which they produce their shrill music. They do not beat these drums, but cause them to vibrate by muscles in the body. The musical members of the insect families are in nearly all cases the males, and it 1s usually sup- posed that they give their concerts for the purpose of engaging the females, but that this is so in all cases wecan not be certain.
The musical instru- ments of the katydids are quite different from those of the grasshoppers, _ being
situated on the over-
a
THE GRASSHOPPER’S COUSINS
lapping bases of the front wings, or tegmina. On this account the front wings of the males are always different from those of the females, the latter retaining the usual or primitive structure. The right wing of a female in one of the more grasshopperlike species, Orchelimum Jaticauda (Fig. 30), is shown at C of Figure 18. The wing is trav- ersed by four principal veins springing from the base. The one nearest the inner edge is called the cubitus (Cu) and the space be- tween it and this margin of the wing is filled with a network of small veins having no particular ar- rangement. In the wings of the male, however, shown at A of the same figure, this inner basal field is much enlarged and consists of a thin, crisp membrane (7m), braced by a number of veins branching from the cubitus (Cu). One of
these (fv), running cross- wise through the mem- brane, is very thick on the left wing, and when the wing is turned over (B) it is seen to have a close series of small cross- ridges on its under sur- face which convert it into
Fic. 19. Wings, sound-making organs, and the “ears” of a conehead grasshopper, Neoconocephalus ensiger, a member of the katydid family A, B, right and left wings, showing the scraper (s) on the right, and the file vein (fe) on the left. C, under surface of the file vein, showing the file (f). D, front leg, showing slits (e) on the tibia opening into pockets containing the hearing organs (fig. 20 A)
a veritable file (f). On the right wing this same vein is much more slender and its file is very weak, but on the basal angle of this wing there is a stiff ridge (s) not de- veloped on the other. The katydids always fold the
[35]
&
INSECTS
wings with the /eft overlapping the right, and in this position the file of the former lies above the ridge (s) of the latter. If now the wings are moved sidewise, the f/e grating on the ridge or scraper causes a rasping sound, and this is the way the katydid makes the notes of its music. _The tone and volume of the sound, however, are probably in large part produced by the vibration of the thin basal membranes of the wings, which are called the tympana (Tm).
The instruments of different players differ somewhat in the details of their structure. There are variations in the form and size of the file and the scraper on the wings of dif- ferent species, and differences in the veins supporting the tympanal areas, as shown in the drawings of these parts from a conehead (Fig. 27) given at A, B, and C, of Figure ig. In the true katydid, the greatest singer of the family, the file, the scraper, the tympana, and the wings them- selves (Fig. 26) are all very highly developed to form an instrument of great efficiency. But, in general, the instru- ments of different species do not Bice: nearly so much as do the notes produced from them by their owners. An endless number of tunes may be played upon the same fiddle. With the insects each musician knows only one tune, or a few simple variations of it, and this he has in- herited from his ancestors along with a knowledge of how to play it on his inherited instrument. The stridulating organs are not functionally developed until maturity, and then the insect forthwith plays his native air. He never disturbs the neighbors with doleful notes while learning.
Very curiously, none of the katydids nor any member of their family ha; the earlike organs on the sides of the body possessed by the locusts. What are commonly supposed to be their organs of hearing are located in their front legs, as are the similar organs of the crickets. Two vertical slits on the upper parts of the shins, or /1d/ae (Fig. 19 D, e), open each into a small pocket (Fig. 20 A, E) with a tym- panumlike membrane (Tm) stretched across its inner wall. Between the membranes are air cavities (Tra) and a com-
[ 36 |
THE GRASSHOPPER’S COUSINS
plicated sensory receptive apparatus (B) connected by a nerve through the basal part of the leg with the central nervous system.
There are several groups of katydids, classed as sub-
‘
‘aie
i
98)
Fic.20. The probable auditory organ of the front leg of Decticus, a member of the katydid family. (Simplified from Schwabe) A, cross-section of the leg through the auditory organ, showing the ear slits (e, e) leading into the large ear cavities (EZ, E) with the tympana (7m, Tm) on their inner faces. Between the tympana are two tracheae (Tra, Tra) dividing the leg cavity into an upper and a lower channel (BC, BC). The sensory apparatus forms a crest on the outer surface of the inner trachea, each ele- ment consisting of a cap cell (CC/), an enveloping cell (EC/) con- taining a sense rod (Sco), and a sense cell (SC/). Ct, the thick
cuticula forming the hard wall of the leg B, surface view of the sensory organ, showing the elements graded in size from above downward. The sense cells (SC/) are attached to the nerve (Nv) along the inner side of the leg
families. A subfamily name ends in inae to distinguish it
from a family name, which, after the Latin fashion, termi- nates in idae.
THE ROUND-HEADED KATYDIDS
The members of this first group of the katydid family are characterized by having large wings and a smooth
ise)
INSECTS
round forehead. They compose the subfamily Phanerop- terinae, which includes species that attain the acme of grace, elegance, and refinement to be found in the entire orthopteran order. Nearly all the round-headed katydids are musical to some degree, but their productions are not
Vi,
Fic. 21. A bush katydid, Scuddéria furcata
Upper figure, a male; lower, a female in the act of cleaning a
hind foot
of a high’ order. On the other hand, though their notes are in a high key, they are usually not loud and not of the kind that keep you awake at night.
Among this group are the bush katydids, the species of which are of medium size with slenderer wings than the others, and are comprised in the genus usually known as Scudderia but also called Phaneroptera. They have ac- quired the name of bush katydids because they are usually found on low shrubbery, particularly along the edges of moist meadows, though they inhabit other places, too, and their notes are often heard at night about the house. Our
[ 38]
THE. GRASSHOPPER’S COUSINS
commonest species, and one that occurs over most of the United States, is the fork-tailed bush katydid (Scudderia furcata). Figure 21 shows a male and a female, the female in the act of cleaning the pads on one of her hind feet. The katydids are all very particular about keeping their feet clean, for it is quite essential to have their adhesive pads always in perfect working order; but they are so con- tinually stopping whatever they may be doing to lick one foot or another, like a dog scratching fleas, that it looks more like an ingrown habit with them than a necessary act of cleanliness. The fork-tailed katydid is an unpreten- tious singer and has only one note, a high-pitched zeep re- iterated several times in succession. But it does not re- peat the series continuously, as most other singers do, and its music is likely to be lost to human ears in the general din from the jazzing bands of crickets. Yet occasionally its soft zeep, zeep, zeep may be heard from a near-by bush or from the lower branches of a tree.
The notes of other species have been described as zkk, zikk, zikk, or zeet, zeet, zeet, and some observers have re- corded two notes for the same species. Thus Scudder says that the day notes and the night notes of Scudderia curvi- cauda differ considerably, the day note being represented by ézrwi, the night note, which is only half as long as the other, by ¢chw. (With a little practice the reader should be able to give a good imitation of this katydid.) Scudder furthermore says that they change from the day note to the night note when a cloud passes over the sun as they are singing by day.
The genus 4mé/ycorypha includes a group of species hav- ing wider wings than those of the bush katydids. Most of them are indifferent singers; but one, the oblong-winged katydid (4. oblongifolia), found over all the eastern half of the United States and southern Canada, is noted for its large size and dignified manners. A male (Fig. 22), kept by the writer one summer in a cage, never once lost his decorum by the humiliation of confinement. He lived ap-
[39 |
INSECTS
parently a natural and contented life, feeding on grape leaves and on ripe grapes, obtaining the pulp of the latter by gnawing holes through the skin. He was always sedate, always composed, his motions always slow and deliberate. In walking he carefully lifted each foot and brought the leg
forward with a steady movement to the new position,
where the foot was carefully set down again. Only in the act of jumping did he ever make a quick movement of any sort. But his preparations for the leap were as calm and unhurried as his other acts: pointing the head upward, dipping the abdomen slowly downward, the two long hind legs bending up in a sharp inverted V on each side of the body, he would lead one to think he was deliberately pre- paring to sit down on a tack; but, all at once, a catch seems to be released somewhere as he suddenly springs upward into the leaves overhead at which he had taken such long and careful aim.
For a long time the aristocratic prisoner uttered no sound, but at last one evening he repeated three times a
[ 40 |
THE GRASSHOPPER’S COUSINS
squeaking note resembling shriek with the s much aspi- rated and with a prolonged vibration on the ze. The next evening he played again, making at first a weak swish, swish, swish, with the s very sibilant and the 7 very vibra- tory. But after giving this as a prelude he began a sh Ill shrie-e-e-e-k, shrie-e-e-e-k, repeated six times, a loud sound described by Blatchley as a “creaking squawk—like the noise made by drawing a fine-toothed comb over a taut string.”
The best-known members of the round-headed katydids, and perhaps of the whole family, are the angular-winged katydids (Fig. 23). These are large, maple-leaf green in- sects, much flattened from side to side, with the leaflike wings folded high over the back and abruptly bent on their upper margins, giving the creatures the humpbacked ap- pearance from which they get their name of angular- winged katydids. The sloping surface of the back in front of the hump makes a large flat triangle, plain in the female, but in the male corrugated and roughened by the veins of the musical apparatus.
There are two species of the angular-winged katydids in the United States, both belonging to the genus Microcen- trum, one distinguished as the larger angular-winged katy- did, M. rhombifolium, and the other as the smaller angu- lar-winged katydid, M. retinerve. The females of the larger species (Fig. 23), which is the more common one, reach a length of 236 melee measured to the tips of the wings. They lay flat, oval eggs, stuck in rows overlapping like scales along the surface of some twig or on the edge of a leaf.
The angular-winged katydids are attracted to lights and may frequently be found on warm summer nights in the shrubbery about the house, or even on the porch and the screen doors. Members of the larger species usually make their presence known by their soft but high-pitched notes resembling /zeet uttered in short series, the first notes re- peated rapidly, the others successively more slowly as the
[41]
INSEGKS
tone becomes also less sharp and piercing. The song may be written /zeet-/zeet-tzeet-tzeet-tzek-tzek-tzek-tzuk-tzuk, though the high key and shrill tones of the notes must be
Fic. 23. The larger angular-winged katydid, Microcentrum rhombifolium
Upper figure, a male; lower, a female
imagined. Riley describes the song as a series of raspings “‘as of a stiff quill drawn across a coarse file,” and Allard
[ 42 ]
HE GRASSHOPPER’S COUSINS
says the notes “‘are sharp, snapping crepitations and sound like the slow snapping of the teeth of a stiff comb as some object is slowly drawn across it.’’ He represents them thus: fek-ek-ek-ek-ek-ek-ek-ek-ek-ek-ek-tzip. But, however the song of Microcentrum is to be translated into English, it contains no suggestion of the notes of his famous cousin, the true katydid. Yet most people confuse the two species, or rather, hearing the one and seeing the other, they draw the obvious but erroneous conclusion that the one seen makes the sounds that are heard.
The smaller angular-winged katydid, Microcentrum reti- nerve, 1s not so frequently seen as the other, but it has simi- lar habits, and may be heard in the vines or shrubbery about the house at night. Its song is a sharp zeet, eet, zeet, the three syllables spaced as in ka-ty-did, and it is probable that many people mistake these notes for those of the true katydid.
The angular-winged katydids are very gentle and un- suspicious creatures, allowing themselves to be picked up without any attempt at escaping. But they are good flyers, and when launched into the air sail about like minia- ture airplanes, with their large wings spread out straight on each side. When at rest they have a comical habit of leaning over sidewise as 1f their flat forms were top-heavy.
LHE, TRUE KATYDID
We now come to that artist who bears by right the name
f ““katydid,” the insect (Fig. 24) known to science as Pterophylla camellifolia and to the American public as the greatest of insect singers. Whether the katydid is really a musician or not, of course, depends upon the critic, but of his fame there can be no question, for his name is a house- hold term as familiar as that of any of our own great artists, notwithstanding that there is no phonographic record ine his music. To be sure, the cicada has more of a world-wide reputation than the katydid, for he has repre- sentatives in many lands, but he has not put his song into
[ 43 ]
INSECTS
words the public can understand. And if simplicity be the test of true art, the song of the katydid stands the test, for nothing could be simpler than merely katy-did, or its easy variations, such as katy, katy- she-did, and katy-didn’t.
Yet though the music of the katydid is known by ear or by reputation to almost every native American, few of us
Fic. 24. The true katydid, Pterophylla camellifolia, a male
are acquainted with the musician himself. This is because he almost invariably chooses the tops of the tallest trees for his stage and seldom descends from it. His lofty platform, moreover, is also his studio, his home, and his world, and the reporter who would have a personal interview must be efficient in tree climbing. Occasionally, though, it happens that a singer may be located in a smaller tree where access to him is easier or from which he may be dislodged by shaking. A specimen, secured in this way on August 12 lived till October 18 and furnished material for the follow: ing notes:
The physical characters of the captive and some of his attitudes are shown in Figures 24 and 25. His length is 134 inches from the forehead to the tips of the folded wits: the front legs are longer and thicker than in most other members of the family, while the hind legs are un- usually short. The antennae, though, are extremely long, slender, and very delicate filaments, 2'’/16 inches in length.
1 44 |
THE GRASSHOPPER’S COUSINS
z Ren
Fic. 25. The katydid in various attitudes A, usual position of a male while singing. B, attitude while running rapidly on a smooth surface. C, preparing to leap from a vertical surface. D, a male, seen from above, showing the stridulating area at the base of the wings. E, a female, showing the broad, flat, curved ovipositor
[45 |
INSECWS
Between the bases of the antennae on the forehead there is a small conical projection, a physical character which separates the true katydid from the round-headed katy- dids and assigns him to the subfamily called the Pseudo- phyllinae, which includes, besides our species, many others that live mostly in the tropics. The rear margins of the wings are evenly rounded and their sides strongly bulged outward as if to cover a very plump body, but the space between them is mostly empty and probably forms a resonance chamber to give tone and volume to the sound produced by the stridulating parts. What might be the katydid’s waistcoat, the part of the body exposed beneath the wings, has a row of prominent buttonlike swellings along the middle which rhythmically heave and sink with each respiratory movement. All the katydids are deep abdominal breathers.
The color of the katydid is plain green, with a conspicu- ous dark-brown triangle on the back covering the stridulat- ing area of the wings. The tips of the mouth parts are yellowish. The eyes are of a pale transparent green, but
each has a dark center which, like the pupil in a painting, 1s always fixed upon you from oiheneaee angle you retreat.
The movements of the captive individual are slow, though in the open he can run rather rapidly, and when he is in a hurry he often takes the rather absurd attitude shown at B of Figure 25, with the head down and the wings and body elevated. He never flies, and was never seen to spread his wings, but when making short leaps the wings are slightly fluttered. In preparing for a leap, if only one of a few inches or a foot, he makes very careful preparations, scrutinizing the proposed landing place long and closely, though perhaps he sees better in the dark and acts then with more agility. If the leap is to be made from a horizontal surface, he slowly crouches with the legs drawn together, assuming an attitude more familiar in a
cat; but, if the jump ts to be from a vertical support, he raises himself on his long front legs as at C of Figure 25,
[ 46 J
THE GRASSHOPPER’S COUSINS
suggesting a camel browsing on the leaves of a tree. He sparingly eats leaves of oak and maple supplied to him in his cage, but appears to prefer fresh fruit and grapes, and relishes bread soaked in water. He drinks rather less than most orthopterons.
When the katydids are singing at night in the woods they appear to be most wary of disturbance, and often the voice of a person approaching or a crackle underfoot is sufficient to quiet a singer far overhead. The male in the cage never utters a note until he has been in darkness and quiet for a considerable time. But when he seems to be assured of solitude he starts his music, a sound of tremendous volume in a room, the tones incredibly harsh and rasping at close range, lacking entirely that melody they acquire with space and distance. It is only by extreme caution that the per- former may be approached while singing, and even then the brief flash of a light is usually enough to silence those stentorian notes. Yet occasionally a glimpse may be had of the musician as he plays, most frequently standing head downward, the body braced rather stiffly on the legs, the front wings only slightly elevated, the tips of the hind wings projecting a little from between them, the abdomen depressed and breathing strongly, the long antennal threads waving about in all directions. Each syllable ap- pears to be produced by a separate series of vibrations made by a rapid shufling of the wings, the middle one be- ing more hurried and the last more conclusively stressed, thus producing the sound so suggestive of ka-ty-did’, ka-ty- did’, which is repeated regularly about sixty times a minute on warm nights. Usually at the start, and often for some time, only two notes are uttered, ka-ty, as if the player has difficulty i in falling at once into the full swing of ka-ty-did.
The structure of the wings and the details of the stridu- lating parts are shown in Figure 26. The wings (A, B) fold vertically against the sides of the body, but their inner basal parts form wide, stiff, horizontal, triangular flaps that overlap, the left on top of the right. A thick, sunken,
[ 47 ]
INSECTS
crosswise vein (fv) at the base of the left tympanum (7m) is the file vein. It is shown from below at C where the broad, heavy file (f) is seen with its row of extremely coarse rasping ridges. The same vein on the right wing (B) is much smaller and has no file, but the inner basal angle of the tympanum is produced into a large lobe bear- ing a strong scraper (5) on its margin.
The quality of the katy- did’s song seems to differ somewhat in different parts of the country. In the vicin- ity of Washington, the in- sects certainly say ka-ty-did as plainly as any insect could. Of course, the sound is more literally to be represented as ka ki-kak’, accented on the last syllable. When only two syllables are pronounced they are always the first two. Sometimes an individual in a band utters four syllables, “katy-she-did” or ka ki-ka- kak’, and again a whole band
Frc. 26. Wings and the sound-mak- 1S heard singing in four notes
ing organs of the male katydid with only an occasional
A font wing sowing heart” Singer giving three. Itis said
thick file vein (fo). B, base of right that in certain parts of the
fore wing with res seraper om South the katydid is called
vein. GC, under surface of file veinof a “‘ cackle - jack,” a name
ch be es > fat, Which, it must be admitted,
is a very literal translation of
the notes, but one lacking in sentiment and unbefitting an artist of such repute. In New England, the katydids heard by the writer in Connecticut and in the western part of Massachusetts uttered only two syllables much
[ 48 ]
THE GRASSHOPPER’S COUSINS
more commonly than three, and the sounds were extremely harsh and rasping, being a loud sgud-wik’, squa-wak', squa-wak’, the second syllable a little longer than the first. This is not the case with those that sey ka-ty. When there were three syllables the series was squa-wa- wak’. Tf all New England katydids sing thus, it is not surprising that some New England writers have failed to see how the insects ever got the name of “‘katydid.” Scudder says “their notes have a shocking lack of melody”; he rep- resents the sound by xr, and records that ‘the song is usually of only two syllables. “That is,” he says, “ they rasp their fore wings twice rather chan thrice; these two notes are of equal (and extraordinary) emphasis, the latter about one-quarter longer than the former; or if three notes are given, the first and second are alike and a little shorter than the last.”
When we listen to insects singing, the question always arises of why they sing, and we might as well admit that we do not know what motive impels them. It is prob- ably an instinct with males to use their stridulating organs, but in many cases the tones emitted are clearly modified by the physical or emotional state of the player. The music seems in some way to be connected with the mating of the sexes, and the usual idea is that the sounds are attractive to the females. With many of the crickets, however, the real attraction that the male has for the female is a liquid exuded on his back, the song apparently being a mere ad- vertisement of his wares. In any case the ecstacies of love and passion ascribed to male insects in connection with their music are probably more fanciful than real. The subject is an enchanted field wherein the scientist has most often weakened and wandered from the narrow path of observed facts, and where he has indulged in a free- dom of imagination permissible to a poet or to a newspaper reporter who wishes to enliven his chronicle of some event in the daily news, but which does not contribute anything substantial to our knowledge of the truth.
[49 ]
INSECTS
THE CONEHEADS
This group of the katydid family contains slender, grasshopperlike insects that have the forehead produced into a_ large } ; cone and the face strongly receding, but which also pos- sess long, slen- der antennae that distinguish them from the true or short- horn grasshop- pers. They con- stitute the sub- family Copi- phorinae. One of the
commonest and Fic. 27. A conehead grasshopper, or katydid, Neocono- most widel y cephalus retusus
Upper figure, a male; lower, a female, with extremely long distributed of ovipositor the larger cone-
heads is the species known as Neoconocephalus ensiger, or the ““sword- bearing conehead.” It is the female, however, that carries the sword; and it is not a sword either, but merely the immensely long egg-laying instrument properly called the ovipositor. The female conehead shown at B of Figure 27, has a similar organ, though she belongs to a species called retusus. The two species are very similar in all respects except for slight differences in the shape of the cone on the head. They look like slim, sharp-headed grasshoppers, 11% to 134 inches in length, usually bright green in color, though sometimes brown.
| 50]
THE GRASSHOPPER’S COUSINS
The song of evsiger sounds like the noise of a miniature sewing machine, consisting merely of a long series of one note, fick, tick, tick, tick, etc., repeated indefinitely. Scudder says evsiger begins with a note like drw, then pauses an instant and immediately emits a rapid succession of sounds like chwi at the rate of about five per second and continues them an unlimited time. McNeil repre- sents the notes as zip, zip, zip; Davis expresses them as 7k, ik, ik; and Allard hears them as ¢s7p, ¢sip, tsip. The song of retusus (Fig. 27) is quite different. It consists of a long shrill whir which Rehn and Hebard describe as a continuous zeeeeeeeeee. The sound is not loud but is in a very high key and rises in pitch as the player gains speed in his wing movements, till to some human ears it becomes almost in- audible, though to others it is a plain and distinct screech.
A large conehead and one with a much stronger instrument is the robust conehead, Neoconocephalus robustus (Fig. 28). He is one of the loudest singers of North American Orthoptera, his song being an intense, continuous buzz, Fic. 28. The robust cone- somewhat resembling that of a eae Detar Gah cicada. A caged specimen singing fore wings separated and
somewhat elevated, the head in a room makes a deafening noise. Ae era! The principal buzzing sound is ac- companied by a lower, droning hum, the origin of which is not clear, but which is probably some secondary vibra- tion of the wings. The player always sits head downward
Se]
INSECTS
while performing, and the breathing motions of the abdo- men are very deep and rapid. The robust conehead is an inhabitant of dry, sandy places along the Atlantic coast from Massachusetts to Virginia and, according to Blatch- ley, of similar places near the shores of Lake Michigan in Indiana. The writer made its acquaintance in Con- necticut on the sandy flats of the Quinnipiac Valley, north of New Haven, where its shrill song may be heard on summer nights from long distances.
THE MEADOW GRASSHOPPERS
These are trim, slim little grasshopperlike insects, active by day, that live in moist meadows where the vegetation 1s always fresh and juicy. They constitute the subfamily Conocephalinae of the katydid family, having conical
Fic. 29. The common meadow grasshopper, Orchelimum vulgare, a member of the katydid family
heads like the last group, but being mostly of smaller size. There are numerous species of the meadow grasshoppers, but most of them in the eastern part of the United States belong to two genera known as Orchelimum and Conoceph- alus. The most abundant and most widely distributed member of the first is the common meadow grasshopper, Orchelimum vulgare. A male is shown in Figure 29. He is a little over an inch in length, with head rather large for his size and with big eyes of a bright orange color. The ground color of his body is greenish, but the top of the head and the thoracic shield is occupied by a long tri- angular dark-brown patch, while the stridulating area of
[52a]
HE GRASSHOPPER’S COUSINS
Fic. 30. The hand-
some meadow grass-
hopper, Orchelimum laticauda
Upper figure, a male; lower, a female
lable repeated many times. These two elements, the z7p and zee, are charac- teristic of the songs of all the Orcheli- mums, some giving more stress to the first and others to the second, and
the wings is marked by a brown spot at each corner. These little grasshoppers readily sing in con- finement, both in the day and at night. Their music is very unpre- tentious and might easily be lost out of doors, consisting mostly of a soft, rustling buzz that lasts two or three seconds. Often the buzz is preceded or followed by a series of clicks made by a slower movement of the wings. Frequently the player opens the wings for the start of the song with a single click, then proceeds with the buzz, and finally closes with a few slow movements that produce the con- cluding series of clicks. But very commonly he gives only the buzz without prelude or staccato end- ing.
Another com- mon member of the genus is the agile meadow grasshopper, Or- chelimum agile. Its music is said to be a long zp, 1p, ZIP, Zee-e-e-€,
with the z7p syl-
Fic. 31. The slender
meadow grasshopper,
Conocephalus fasciatus,
one of the smallest
members of the katy- did family
[53]
INSECTS
sometimes either one or the other 1s omitted. A very pretty species of the genus is the handsome meadow grasshopper, Orchelimum laticauda (or pulchellum) shown in Figure 30, When at rest, both males and females usually sit close to a stem or leaf with the middle of the body in contact with the support and the long hind legs stretched out behind. Davis says the song of this species iS a 2p, 2p, Zap ez, 2, Guiie distinguishable from that of O. vulgare.
Still smaller meadow grasshoppers belong to the genus Conocephalus, more commonly called Xiphidium. One of the most abundant species, the slender meadow grass- hopper, C. fasciatus, is shown in Figure 31. It is less than an inch in length, the body green, the back of the thorax dark brown, the wings reddish-brown, and the back of the abdomen marked with a broad Ceoean stripe. Allard says the song of this little meadow grasshopper may be ex- pressed as lip, tip, tip, tseeeeeeeeeeeeee, but that the entire song is so faint as almost to escape the hearing. Piers describes it as ple-e-e-e-e-e, (zit, (zit, fzit, tzit. Like the song of Orchelimum vulgare it apparently may either begin or end with staccato notes.
THE SHIELD BEARERS
Another large group of the katydid family is the sub- family Decticinae, mostly cricketlike insects that live on the ground, but which have wings so short (Fig. 32) that they are poor musicians. They are called “‘shield bearers” because the large back plate of the first body segment is more or less prolonged like a shield over the back. Most of the species live in the western parts of the United States, where the individuals sometimes become so abundant as to form large and very destructive bands. One such species 1s the Mormon cricket, 4xabrus simplex, and an- other is the Coulee cricket, Peranabrus scabricollis (Fig. 32), of the dry central region of the State of Washington. The females of these species are commonly wingless, but the
[54 |
THE GRASSHOPPER’S COUSINS
males have short stubs of front wings that retain the stridulating organs and enable them to sing with a brisk chirp.
Still another large subfamily of the Tettigoniidae is the
Fic. 32. The Coulee cricket, Peranabrus scabricollis, male and female, an example of a cricketlike member of the katydid family
Rhadophorinae, including the insects known as “camel crickets.”’ But these are all wingless, and therefore silent.
Tue Cricket Famity
The chirp of the cricket is probably the most familiar note of all orthopteran music. But the only cricket com- monly known to the public is the black fteld cricket, the lively chirper of our yards and gardens. His European cousin, the house cricket, is famous as the “cricket on the hearth” on account of his fondness for fireside warmth which so stimulates him that he must express his animation in song. This house cricket has been known as Gryllus since the time of the ancient Greeks and Romans, and his name has been made the basis for the name of his family, the Gryllidae, for there are numerous other crickets, some that live in trees, some in shrubbery, some on the ground, and others in the earth.
The crickets have long slender antennae like those of the katydids, and also stridulating organs on the bases of the wings, and ears in their front legs. But they differ from the katydids in having only three joints in their feet (Fig. 17 C). The cricket’s foot in this respect resembles the foot
[55]
INSEGES
of the grasshopper (A), but usually differs from that of the grasshopper in having the basal joint smooth or hairy all around or with only one pad on the under surface. In most crickets, also, the second joint of the foot is very small.
ys see EL LILA SLR RE weet eee ee eee Doon = =
Fic. 33. The wings of a tree cricket
A, right front wing of an immature female, showing normal arrangement of veins: Sc, subcosta; R, radius; M, media; Cu, first branch of cubitus; Cue, second branch of cubitus; 74, first anal. (From Comstock and Needham)
B, front wing of an adult female of the narrow-winged tree cricket
C, front wing of an immature male, showing widening of inner half to form vibrating area, or tympanum, and modification of veins in this area. (From Comstock and Needham)
D, right front wing of adult male of the narrow-winged tree cricket; the second branch of cubitus (Cuz) becomes the curved file vein (fv); s, the scraper
Some crickets have large wings, some small wings, some no wings at all. The females are provided with long oviposi- tors for placing their eggs in twigs of trees or in the ground (Figs. 35, 36).
The musical or stridulating organs of the crickets are similar to those of the katydids, being formed from the veins of the basal parts of the front wings. But in the crickets the organs are equally developed on each wing, and it looks as if these insects could play with either wing up- permost. Yet most of them consistently keep the right
[ 56 |
Por
THE GRASSHOPPER’S COUSINS
wing on top and use the file of this wing and the scraper of the left, just the reverse of the custom among the katydids.
The front wings of male crickets are usually very broad and have the outer edges turned down in a wide flap that folds over the sides of the body when the wings are closed. The wings of the females are simpler and usually smaller. The differences between the front wings in the male and the female of one of the tree crickets (Fig. 37) is shown at B and D of Figure 33. The inner half of the wing (or the rear half when the wing is extended) is very large in the male (D) and has only a few veins, which brace or stiffen the wide membranous vibratory area or tympanum. The inner basal part, or ana/ area, of the male wing is also larger than in the female and contains a prominent vein (Cuz) which makes a sharp curve toward the edge of the wing. This vein has the stridulating file on its under sur- face. The veins in the wing of an adult female (B) are comparatively simple, and those of a young female (A) are more so. But the complicated venation of the male wing has been de- veloped from the simple type of the female, which is that common to in- sects in general. The wing of a young male (C) is not so different from that of a young female (A) but that the cor- responding veins can be identified, as shown by the lettering. Taking next the wing of the adult male (D), it is an easy matter to determine which veins
3 Fic. 34. A mole cricket, have been distorted to produce the Neocurtilla hexadactyla
stridulating apparatus. When the tree crickets sing they elevate the wings above the back like two broad fans (Figs. 37, 40) and move them sidewise so
that the file of the right rubs over the scraper of the left.
[57]
INSECUS
THE MOLE CRICKETS
The mole crickets (Fig. 34) are solemn creatures of the earth. They live like true moles in burrows underground, usually in wet fields or along streams. Their forefeet are broad and turned outward for digging like the front feet of moles. But the mole crickets differ from real moles in having wings, and sometimes they leave their burrows at night and fly about, being occasionally attracted to lights. Their front wings are short and lie flat on the back over the base of the abdomen, but the long hind wings are folded lengthwise over the back and project beyond the tip of the body.
Notwithstanding the gloomy nature of their habitat, the male mole crickets sing. Their music, however, 1s a sleone and monotonous, being always a series of loud, deep-toned chirps, like churp, churp, churp, repeated very regularly about a hundred times a minute and continued indefinitely if the singer is not disturbed. Since the notes are most frequently heard coming from a marshy field or from the edge of a stream, they might be supposed to be those of a small frog. It is difficult to capture a mole cricket in the act of singing, for he is most likely standing at an opening in his burrow into which he retreats before he is discovered.
THE FIELD CRICKETS
This group of crickets includes Gry//us as its typical member, but entomologists give first place to a smaller brown cricket called Nemobius. There are numerous spe- cies of this genus, but a widely distributed one is N. vitta- tus, the striped ground cricket. This is a little cricket, about three-eighths of an inch in length, brownish in color, with three darker stripes on the abdomen, common in fields and dooryards (Fig. 35). In the fall the females lay their eggs in the ground with their slender ovipositors (D, E) and the eggs (F) hatch the following summer.
The song of the male Nemobius is a continuous twitter-
[58]
THE GRASSHOPPER’S COUSINS
Fic. 35. The striped ground cricket, Nemobius vittatus
A, B, females, distinguished by the long ovipositor. C,a male. D, a female
in the act of thrusting her ovipositor into the ground. E, a female, with oviposi-
tor full length in the ground, and extruding an egg from its tip. F, an eggin the ground
ing trill so faint that you must listen attentively to hear it. In singing the male raises his wings at an angle of about 45°. The stridulating vein is set with such fine ridges that
[59]
INSECTS
they would seem incapable of producing even those whis- pering | Nemobius notes. Most of the muscial instruments of insects can be made to produce a swish, a creak, or a grating noise of some sort when handled with our clumsy fingers or with a pair of forceps, but only the skill of the living insect can bring from them the tones and the volume of sound they are capable of producing.
Our best-known cricket is Gryllus, the black cricket
(Fig. 36), so common everywhere in fields and yards and occasionally entering houses. The true house cricket of Europe, Gry//us domesticus, has become naturalized in this country and occurs in small numbers through the Eastern States. But our common native species is Gry//us assimiits. Entomologists distinguish several varieties, though they are inclined to regard them all as belonging to the one species.
Mature individuals of Gryllus are particularly abundant in the fall; in southern New England they appear every year at this season by the millions, swarming everywhere, hopping across the country roads in such numbers that it is impossible to ride or walk without crushing them. Most of the females lay their eggs in September and October, de- positing them singly in the ground (Fig. 36 D, E) in the same way that Nemobius does. These eggs hatch about the first of June the following year. But at this same time another group of individuals reaches maturity, a group that hatched in midsummer of the preceding year and passed the winter in an immature condition. The males of these begin singing at Washington during the last part of May, in Connecticut the first of June, and may be heard until the end of June. Then there is seldom any sound of Gryllus until the middle of August, when the males of the spring group begin to mature. From now on their notes become more and more common and by early fall they are to be heard almost continuously day and night until frost.
The notes of Gryllus are always vivacious, usually cheer- ful, sometimes angry in tone. gk hey are merely chirps, and
[ 60 |
THE GRASSHOPPER’S COUSINS
may be known from all others by a broken or vibratory sound. There is little music in them, but the player has enough conceit to make up for this lack. Two vigorous
Fic. 36. The common black cricket, Gryllus assimilis
A, a male with wings raised in the attitude of singing. B, a female with long
“ ovipositor. C, young crickets recently hatched (enlarged about 24 times).
D, a female inserting her ovipositor in the ground. E, a female with ovipositor buried full length in the ground
[61]
INSECTS
males that were kept in a cage together with several females gave each other little peace. Whenever one began to play his fiddle the other started up, to the plain disgust of the first one, and either was always greatly annoyed and provoked to anger if any of the females happened to run into him while he was playing. If one male was fiddling alone and the other approached him, the first dashed at the intruder with jaws open, increasing the speed of his strokes at the same time till the notes became almost a shrill whistle. The other male usually retaliated by play- ing, too, In an apparent attempt to outfiddle the first. The chirps from both sides now came quicker and quicker, their pitch mounting higher and higher, till each player reached his limit. Then both would stop and begin over again. Neither male ever inflicted any actual damage on his rival, and in spite of their savage threats neither was ever seen really to grasp any part of the other with his jaws. Either would dash madly at a female that happened to disturb him while fiddling, but neither was ever seen to threaten a female with open jaws.
The weather has much influence on the spirits of the males; their chirps are always loudest and their rivalry keenest when it is bright and warm. Setting their cage in the sun on cold days always started the two males at once to singing. Out of doors, though the crickets sing in all weather and at all hours, variations of their notes in tone and strength according to the temperature are very notice- able. This is not owing to any effect of humidity on their instruments, for the two belligerent males kept in the house never had the temper on cold and gloomy days that char- acterized their actions and their song on days that were warm and bright. This, in connection with the fact that their music is usually aimed at each other in a spirit clearly suggestive of vindictiveness and anger, is all good evidence that Gryllus sings to express himse/f and not to “charm the females.” In fact, it is often hard to feel certain whether he is singing or swearing. If we could understand the
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WME GRASSHOPPER’S COUSINS
words, we might be shocked at the awful Janguage he is hurling at his rival. However, swearing is only a form of emotional expression, and singing is another. Gryllus, like an opera singer, simply expresses a// his emotions in music, and, whether we can understand the words or not, we page cad the sentiment.
At last one of the two caged rivals died; whether from natural causes or by foul means was never ascertained. He was alive early on the day of his demise but apparently weak, though still intact. In the middle of the afternoon, however, he lay on his back, his hind legs stretched out straight and stiff; only a few movements of the front legs showed that life was not yet quite extinct. One antenna was lacking and the upper lip and adjoining parts of the face were gone, evidently chewed off. But this is not neces- sarily evidence that death had followed violence, for, in cricketdom, violence more commonly follows death; that is, cannibalism is substituted for interment. A few days before, a dead female in the cage had been devoured quickly, all but the skull. After the death of this male, the remaining one no longer fiddled so often, nor with the same sharp challenging tone as before. Yet this could not be attributed to sadness; he had despised his rival and had clearly desired to be rid of him; his change was due rather to the lack of any special stimulus for expression.
Ln SRE CRICKETS
The unceasing ringing that always rises on summer eve- nings as soon as the shadows begin to darken, that shrill melody of sound that seems to come from nothing but from everywhere out of doors, is mostly the chorus of the tree crickets, the blend of notes from innumerable harpists playing unseen in the darkness. This sound must be the most familiar of all insect sounds, but the musicians them- selves are but little known to the general public. And when one of them happens to come to the window or into the house and plays in solo, the sound is so surprisingly
[ 63 |
INSECTS
loud that the player is not suspected of being one of that band whose mingled notes are heard outside softened by distance and muffled by screens of foliage.
Out of doors the music of an individual cricket is so elusive that even when you think you have located the ex-
Fic. 37. The snowy tree cricket, Oecanthus niveus
The upper figures, males, the one on the right with fore wings raised vertically in attitude of singing; below, a female, with narrow wings folded close against the body
act bush or vine from which it comes the notes seem to shift and dodge. Surely, you think, the player must be under that leaf; but when you approach your ear to it, the sound as certainly comes from another over yonder; but here you are equally convinced that it comes from still
[ 64 |
Tak GRASSHOPPER’S:; COUSINS
another place farther off. Finally, though, it strikes the ear with such intensity that there can be no mistaking the source of its origin, and, right there in plain sight on a leaf sits a little, delicate, slim-legged, pale-green insect with hazy, transparent sails outspread above its back. But can such an insignificant creature be making such a deafen- ing sound! It has required very cautious tactics to ap- proach thus close without stopping the music, and it needs but a touch on stem or leaf to make it cease. But now those gauzy sails that before were a blurred vignette have acquired a definite outline, and a little more disturbance may cause them to be lowered and spread flat on the creature’s back. The music will not begin anew until you have passed a period of silent waiting. Then, suddenly, the lacy films go up, once more their arehees blur, and that intense scream again pierces your ear. In short, you are witnessing a private performance of the broad- winged tree cricket, Oecanthus latipennis.
But if you pay attention to the notes of other singers, you will observe that there is a variety of airs in the medley going on. Many notes are long trills like the one just identified, lasting indefinitely; but others are softer purr- ing sounds, about two seconds in length, while still others are short beats repeated regularly a hundred or more times every minute. The last are the notes of the snowy tree cricket, Oecanthus niveus, so-called on account of his pale- ness. He is really green in color, but a green of such a very pale shade that he looks almost white in the dark. The male (Fig. 37) is a little longer than half an inch, his wings are wide and flat, overlapping when folded on the back, with the edges turned down against the sides of the body. The female is heavier-bodied than the male, but her wings are narrow, and when folded are furled along the back. She has a long ovipositor for inserting her eggs into the bark of trees.
The males of the snowy cricket reach maturity and begin to sing about the middle of July. The singer raises his
[65 ]
INSECTS
wings vertically above the back and vibrates them sidewise so rapidly that they are momentarily blurred with each note. The sound is that freat, treat, treat, treat already de- scribed, repeated regularly, rhythmically, and monoto- nously all through the night. At the first of the season there may be about 125 beats every minute, but later, on hot nights, the strokes become more rapid and mount to 160 a minute. In the fall again the rate decreases on cool evenings to perhaps a hundred. And finally, at the end of the season, when the players are benumbed with cold, the
Fic. 38. Distinguishing marks on the basal segments of the antennae of common species of tree crickets
A, B, narrow-winged tree cricket, Oecanthus angustipennis. .C»
snowy tree cricket, miveus. D, four-spotted tree cricket, migri@
cornis quadripunctatus. E, black-horned tree cricket, nigricornis: F, broad-winged tree cricket, /atipennis
notes become hoarse bleats repeated slowly and irregularly as if produced with pain and difficulty.
The several species of tree crickets belonging to the genus Oecanthus are similar in appearance, though the males differ somewhat in the width of the wings and some species are more or less diffused with a brownish color. But on their antennae most species bear distinctive marks (Fig. 38) by which they may be easily identified. The snowy cricket, for example, has a single oval spot of black on the under side of each of the two basal antennal joints (Fig. 38 C). Another, the narrow-winged tree cricket, has
[ 66 |
THE GRASSHOPPER’S COUSINS
a spot on the second joint and a black J on the first (A, B). A third, the four-spotted cricket (D), has a dash and dot side by side on each joint. A fourth, the black-horned or striped tree cricket (E), has two spots on each joint more or less run together, or sometimes has the whole base of the antenna blackish, while the color may also spread over the fore parts of the body and, on some individuals, form
Fic. 39. Male and female of the narrow-winged tree cricket, Oecanthus angusti- pennis
The female is feeding on a liquid exuded from the back of the male, while the latter holds his fore wings in the attitude of singing. (Enlarged about 3 times) stripes along the back. Ai fifth species, the broad-winged (F), has no marks on the antennae, which are uniformly
brownish.
The narrow-winged tree cricket (Oecanthus angusti- pennis) is almost everywhere associated with the snowy, but its notes are very easily distinguished. They consist of slower, purring sounds, usually prolonged about two seconds, and separated by intervals of the same length, but as fall approaches they become slower and longer. Always they are sad in tone and sound far off.
The three other common tree crickets, the black-horned or striped cricket, Oecanthus nigricornis, the four-spotted,
[ 67 |
INSECYs
O. nigricornis quadripunctatus, and the broad-winged, O. /ati- pennis, are all trillers; that 1s, their music consists oF a long, shrill whir kept up indefinitely. Of these the broad-winged cricket makes the loudest sound and the one predominant near Washing- ton. The black-horned is the common triller farther north, and is particularly a daylight singer. In Connecticut his shrill note rings everywhere along the road- sides, on warm bright afternoons
Fic. 40. A male of the broad- ~— of September and October, as the
winged tree cricket, Oecanthus : Z
latipennis, with wings elevated Player sits on leaf or twig fully
in Position of singing, seen from exposed to the sun. At this above and behind, showing
the basin (B) on his back into | season also, both the snowy and
which the liquid is exuded that the narrow-winged sing by day
attracts the female i but usually later in the after- noon and generally from more concealed places.
We should naturally like to know why these little creatures are such _ persistent singers and of what use their music is to them. Do the males really sing to charm and attract the females as is usually pre- sumed? We do not know; but sometimes when a male is sing- ing, a female approaches him from behind, noses about on his back, and soon finds there a deep basinlike cavity situated just behind the bases of the elevated te en eee ci wings. This basin contains a broad-winged tree cricket, clear liquid which dhe (Sree with its basin (B) that receives
secretion from the glands (G/) proceeds to lap up very eagerly, inside the body
[ 68 ]
THE GRASSHOPPER’S COUSINS
as the male remains quiet with wings upraised though he has ceased to play (Fig. 39). We must suspect, then, that in this case the female has been attracted to the male rather by his confectionery offering than by his music. The purpose of the latter, therefore, would appear to be to advertise to the female the whereabouts of the male, who she knows has sweets to offer; or if the liquid is sour or bitter it is all the same—the female likes it and comes after it. If, now, this luring of the female sometimes ends in marriage, we may see here the real reason for the male’s possessing his music-making organs and his instinct to play them so continuously.
A male cricket with his front wings raised, seen from above and behind as he might look to a female, is shown in Figure 40. The basin (B) on his back is a deep cavity on the dorsal plate of the third thoracic segment. A pair of large branching glands (Fig. 41, G/) within the body open just inside the rear lip of the basin, and these glands fur- nish the liquid that the female obtains.
There is another kind of tree cricket belonging to an- other genus, Neoxadia, called the two-spotted tree cricket, N. bipunctata, on account of two pairs of dark spots on the wings of the female. This cricket 1s larger than any of the species of Oecanthus and 1s of a pinkish brown color. It is widely distributed over the eastern half of the United States, but is comparatively rare and seldom met with. Allard says its notes are low, deep, mellow trills con- tinued for a few seconds and separated by short intervals, as are the notes of the narrow-winged Oecanthus, but that their tone more resembles that of the broad-winged.
THE BUSH CRICKETS
The bush crickets differ from the other crickets in having the middle joint in the foot larger and shaped more like the third joint in the foot of a katydid (Fig. 17 B). Among the bush crickets there is one notable singer common in the
neighborhood of Washington. This is the jumping bush [69]
INSECTS
cricket, Orocharis saltator (Fig. 42), who comes on the stage late in the season, about the middle of August, or shortly after. His notes are loud, clear, piping chirps with a rising inflection toward the end, suggestive of the notes of a small tree toad, and they at once strike the listener as something new and different in the insect program. The play- ers, however, are at first very hard to lo- cate, for they do not perform continuously —one note seems to come from here, a second from over there, and a third from a different an- gle, so that it is al- most impossible to place any one of them. But vafter ya Fic. 42. The jumping bush cricket, Orocharts week or so the crick- saltator ets become more nu- Upper figure, a male; lower, a female merous and each player more persistent till soon their notes are the predomi- nant sounds in the nightly concerts, standing out loud and clear against the whole tree-cricket chorus. As Riley says, this chirp “is so distinctive that when once studied it is never lost amid the louder racket of the katydids and other night choristers.”
After the first of September it is not hard to locate one of the performers, and when discovered with a flashlight, he is found to be a medium-sized, brown, short-legged cricket, built somewhat on the Style of Gr -yllius but smaller (Fig. 42). The male, however, while singing raises his wings straight up, after the manner of the tree crickets, and he too, carries a basin of liquid on his back much sought after
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THE GRASSHOPPER’S COUSINS
by the female. In fact the liquid is so attractive to her that, at least in a cage, she is sometimes so persistent in her efforts to obtain it that the male is clearly annoyed and tries to avoid her. One male was observed to say very distinctly by his actions, as he repeatedly tried to escape the nibbling of a female, presumably his wife since she was taken with him when captured, “I do wish you would quit pestering me and let me sing!” Here is another piece of evidence suggesting that the male cricket sings to express his own emotions, whatever they may be, and not pri- marily to attract the female. But if, as in the case of the tree crickets, his music tells the female where she may find her favorite confection, and this in turn leads to matrimony, when the male is in the proper mood, it suggests a practical use and a rea- son for the stridulating apparatus and the song of the male insect.
WALKING-STICKS AND Lear INSEcTs
Talent often seems to run in families, or in re- lated families, but it does not necessarily express it- self in the same way. If the katydids and crickets
Aron Fic. 43. The common walking-stick in- are noted musicians, sect, Diapheromera femorata, of the eastern
some of their relatives part of the United States. (Length 2% )
inches)
belonging to the family Phasmidae, are incomparable mimics. Their mimicry, however, is not a conscious imitation, but is one bred in their bodily forms through a long line of ancestors.
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INSECTS
If sometime in the woods you should chance to see a short, slender piece of twig suddenly come to life and slowly walk away on six slim legs, the marvel would not be
a miracle, but a walking-stick in-
sect (Fig. 43). These insects are
fairly common in the eastern parts
t | )) of the United States, but on ac-
p as count of their resemblance to twigs, and their habit of remaining perfectly quiet for a long time with the body pressed close to a branch of a tree, they are more frequently overlooked than seen. Sometimes, however, they occur locally in great numbers. It is supposed that the stick insects so closely resemble twigs for the pur- pose of protection from their enemies, but it has not been shown just what enemies they avoid by their elusive shape. The stick in- sects are more common in the South and in tropical countries, where some attain a remarkable length, one species from Africa, for example, being eleven inches long when full-grown. In New Guinea there lives a species that looks more like a small club than
Fic. 44. A gigantic spiny é jf walking-stick insect, Eury- ae stick, It being = large, heavy- canthus horrida, from New bodied, spiny creature, nearly
Guinea. (Length 5%
eS SIX Tene in length and an
inch in width through the thick-
est part of its body (Fig. 44). Other members of the phasmid family have specialized on imitating leaves. These insects have wings in the adult stage, and, of course, the wings make it easier for
[72]
THE GRASSHOPPER’S COUSINS
them to take the form of leaves. One famous species that lives in the East Indies looks so much like two leaves stuck together that it is truly marvelous that an insect could be so fashioned (Fig. 45). The whole body is flat, and about three inches long, the bases of the legs are broad and irregu- larly notched, the abdomen is spread out almost as thin as a real leaf, and the leaflike wings are held close above it. Finally, the color, which is leaf-green or brown, gives the last touch necessary for complete dissim- ulation.
THe Manrtips
It is often observed that genius may be perverted, or put to evil purposes. Here isa family of insects, the Man-
Fic. 45. A tropical Jeaf insect, i Pulchriphyllium pulchrifolium, a tidae, related to the grass- member of the walking-stick fam-
ily. (Length 3 inches)
hoppers, katydids, and crick- ets, the members of which are clever enough, but are deceitful and malicious.
The praying mantis, Stagmomantis carolina (Fig. 46), though he may go by the aliases of ‘“‘rear-horse’”’ and “soothsayer,” gets his more common name from the prayerful attitude he commonly assumes when at rest. The long, necklike prothorax, supporting the small head, is elevated and the front legs are meekly folded. But if you examine closely one of these folded legs, you will see that the second and third parts are armed with suspicious- looking spikes, which are concealed when the two parts are closed upon each other. In truth, the mantis is an arch hypocrite, and his devotional attitude and meek looks betoken no humility of spirit. The spiny arms,
eel
INSECES:
so innocently folded upon the breast, are direful weapons held ready to strike as soon as some unsuspecting insect happens within their reach. Let a small grasshopper come near the posing saint: immediately a sly tilt of the head belies the suppliant manner, the crafty eyes leer upon the approaching insect, losing no detail of his movements. Then, suddenly, without warning, the pray- ing mantis becomes a demon in action. With a nice cal- culation of distance, a swift movement, a snatch of the
Fic. 46. The praying mantis, Stagmomantis carolina, and remains of its last meal. (Length 21% inches)
terrible clasps, the unlucky grasshopper is a doomed captive, as securely held as if a steel trap had closed upon his body. As the hapless creature kicks and wrestles, the jaws of the captor sink into the back of his head, evidently in search of the brain; and hardly do his weakening strug- gles cease before the victim is devoured. Legs, wings, and other fragments unsuitable to the taste of an epicure are thrown aside, when once more the mantis sinks into repose, piously folds his arms, and meekly awaits the
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THE GRASSHOPPER’S COUSINS
chance arrival of the next course in his ever unfinished banquet of living fare.
Some exotic species of mantids have the sides of the prothorax extended to form a wide shield (Fig. 47), beneath which the forelegs are folded and completely hidden. Itis not clear what advantage they derive from this device, but it seems to be one more expression of deceit.
Of course, as we _ shall take occasion to observe later, goodness and _bad- ness are largely matters of relativity.
Fic. 47. A mantis from Ecuador with a shieldlike extension of its back. (Length 334 inches)
The mantis is an evil creature from the standpoint of a grasshopper, but he would be regarded as a benefactor by those who have a grudge against grass- hoppers or against other insects that the mantis destroys. Hence, we must reckon the mantis as at least a bonsioel: insect relative to human welfare. A _ large species of mantis, introduced a few years ago into the eastern States from China, is now regarded as a valuable agricul. tural asset because of the number of harmful insects it destroys.
The mantids lay their eggs in large cases stuck to the twigs of trees (Fig. 48).
Fic. 48. Eggcaseofa The substance of which the case is made mantis attached to a i¢ similar to that with which the locusts
twig, Stagmomantis
carolina inclose their eggs, and is exuded from the
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INSECTS
body of the female mantis when the eggs are laid. The young mantids are active little creatures, without wings but with long legs, and it is the fate of those unprotected green bugs, the aphids, or plant lice, that infest the leaves of almost all kinds of plants, to become the principal victims of their youthful appetites.
CHAPTER Th
ROACHES SAND OLE ANCIENT INSECTS
WE used to speak quite confidently of time as something definite, measurable by the clock, and of a year or a cen- tury as specific quantities of duration. In this present age of relativity, however, we do not feel so certain about these things. Geologists calculate in years the probable age of the earth, and the length of time that has elapsed since certain events took place upon it, but their figures mean only that the earth has gone around the sun approximately so many times during the interval. * In biology it signifies nothing that one animal has been on the earth for a million years, and another for a hundred million, for the unit of evolution is not a year, but a generation. If one animal, such as most insects, has from one to many generations every year, and another, such as man, has only four or five in a century, it is evident that the first, by evolutionary reckoning, will be vastly older than the second, even though the two have made the same number of trips with the earth around the sun. An insect that antedates man by several hundred million years, therefore, is ancient indeed.
The roach scarcely needs an introduction, being quite well known to all classes of society in every inhabited part of the world. That he has long been established in human communities is shown by the fact that the various nations have bestowed different names upon him. His common English name of “cockroach” is said to come from the Spanish, cucaracha. The Germans call him, rather dis- respectfully, AKichenschabe, which signifies “‘kitchen
[77]
INSECTS
louse.” The ancient Romans called him Blatta, and on this his scientific family name of Blattidae is based. A small species of Europe, named by the entomologists
Fic. 49. The four species of common household roaches A, the German roach, or Croton bug, Blattella germanica (Jength % inch). B, the American cockroach, Periplaneta americana (length 13% inches). C, the Australian cockroach, Periplaneta australasiae (length 134 inches). D, the wingless female of the Oriental roach, Blatta orientalis (length 11% inches). E, the winged male of the Oriental roach (length 1 inch)
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ROACHES AND OTHER ANCIENT INSECTS
Blattella germanica, which is now our most common American roach, received the nickname of ‘“‘Croton bug”’ in New York, because somehow he seemed to spread with the introduction of the Croton Valley water system, and this appelation has stuck to him in many parts of the country.
The Croton bug, or German roach (Fig. 49 A), is the smallest of the “domestic” varieties of roaches. It is that rather slender, pale-brown species, about five-eighths of an inch in length, with the two dark spots on the front shield of its body. This roach is the principal pest of the kitchen in the eastern part of the United States, and prob-
OA TUS ir OR Ee bs MOO eE Lier Ate Ley
Fic. 50. Egg cases of five species of roaches. (Twice natural size)
A, egg case of the Australian roach (fig. 49 C). _B, that of the American roach (fig. 49 B); the other three are made by out-of-door species
ably the best support of the trade in roach powders. Sev- eral other larger species are fortunately less numerous, but still familiar enough. Among these are one called the American roach (Fig. 49 B), a second known as the Australian roach (C), and a third as the Oriental roach (D, E). These four species of cockroaches are all great travelers and recognize no ties of nationality. They are equally at home on land and at sea, and, as uninvited
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INSEC IES
passengers on ships, they have spread to all countries where ships have gone.
Besides the household roaches, there are great numbers of species that live out of doors, especially in warm and tropical regions. Most of these are plain brown of various shades, or blackish, but some are green, and a few are spotted, banded, or striped. Different species vary much in size, some of the largest reaching a length of four inches, measured to the tips of the folded wings, while the smallest are no longer than three thirty-seconds of an inch in length. They nearly all have the familiar flattened form, with the head bent down beneath the front part of the body, and the long, slender antennae projecting forward. Most species have wings which they keep closely folded over the back. In the Oriental roach, the wings of the female are very short (Fig. 49 D), a character which gives them such a different appearance from the males (E) that the two sexes were formerly supposed to be different species.
The roach, of course, was not designed to be a household insect, and it lived out of doors for ages before man con- structed dwellings, but it happens that its instincts and its form of body particularly adapt it to a life in houses. Its keen sense, its agility, its nocturnal habits, its omnivorous appetite, and its flattened shape are all qualities very fitting for success as a domestic pest.
Many kinds of roaches give birth to living young; but most of our common species lay eggs, which they inclose in hard-shelled capsules. The material of the capsule is a tough but flexible substance resembling horn, and 1s pro- duced as a secretion by a special gland in the body of the female opening into the egg duct. The capsule is formed in the egg duct, and the eggs are discharged into it while the case is held in the orifice of the duct. When the re- ceptacle is full its open edge is closed, and the eggs are thus tightly sealed within it. The sealed border is finely notched, and transverse impressions on the surface of the capsule indicate the position of the eggs within it.
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ROACHES AND OTHER ANCIENT INSECTS
The Croton bug, or German roach (Fig. 49 A), makes a small flat tabloid egg case, which the female usually carries about with her for some time projecting from the end of her body, and sometimes the eggs hatch while she is still carrying the case. The American and Australian roaches (Fig. 49 B, C) make egg cases much resembling miniature pocketbooks or tobacco pouches, about three-eighths or half an inch in length, with a serrated clasp along the upper edge (Fig. 50 A, B). The cases of some of the smaller species of roaches are only one-sixteenth of an inch long
Fic. 51. Young of the German roach, or Croton bug (fig. 49 A), in various stages just before and after hatching
A, the young roach in the egg just before hatching. B, the young roach just
after hatching, shedding its embryonic covering membrane. C, young roach
after shedding the embryonic covering. D, the same individual half an hour old
(C), while larger species may make a case three-quarters of an inch in length (E).
The embryo roaches mature within the eggs, and when they are ready to hatch they emerge inside the egg case. By some means, the roughened edge of the case where it was last closed is opened to allow the imprisoned insects to escape. Small masses of the tiny creatures now bulge out, and finally the whole wriggling contents of the cap- sule is projecting from the slit. First one or two indi- viduals free themselves, then several together fall out, then more of them, until soon the case containing the empty eggshells is deserted.
[81]
INSECTS
When the young roaches first liberate themselves from the capsule, they are helpless creatures, for each is con- tained in a close-fitting membrane that binds its folded legs and antennae tightly to the body and keeps the head pressed down against the breast (Fig. 51 A). The inclos- ing sheath, however, a film so delicate as to be almost invisible, is soon burst by the struggling of the little roach anxious to be free—it splits and rapidly slides down over the body (B), from which it is at last pushed off. The shrunken, discarded remnant of the skin is now such an insignificant flake that it scarce seems possible it so re- cently could have enveloped the body of the insect.
The newly liberated young roach dashes off on its slim legs with an activity quite surprising 1n a creature that has never had the use of its legs before. It is so slender of figure (Fig. 51 C) that it does not look like a roach, and it is pale and colorless except for a mass of bright green material in its abdomen. But, almost at once, it begins to change; the back plates of the thorax flatten out, the body shortens by the overlapping of its segments, the abdomen takes on a broad, pear-shaped outline, the head is retracted be- neath the prothoracic shield, and by the end of half an hour the little insect is unmistakably a young cockroach (D):
The roaches have a potent enemy in the house centipede, that creature of so many legs (Fig. 52) that it looks like an animated blur as it occasionally darts across the living- room floor or disappears in the shades of the basement before you are sure whether you have seen something or not, but which is often trapped in the bathtub, where its appearance is likely to drive the housewife into hysteria. Unless you are fond of roaches, however, the house centi- pede should be protected and encouraged. The writer once placed one of these centipedes in a covered glass dish containing a female Croton bug and a capsule of her eggs which were hatching. No sooner were the young roaches running about than the centipede began a feast which
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"2
ROACHES AND OTHER ANCIENT INSECTS
ended only when the last of the brood had been devoured. The mother roach was not at the time molested, but next morning she lay dead on her back, her head severed and dragged some distance from the body, which was sucked dry of / its Juices—mute evidence of the js tragedy that had befallen some- / time in the night, probably when the pangs of returning hunger stirred the centipede to renewed activity. The house centipede does not confine itself to a diet of live roaches, for it will eat almost any kind of food, but it is never a pest of the household larder. PBN Most species of roaches have igs:s two pairs of well-developed } wings, which they ordinarily keep folded over the back, for in their usual pursuits the domestic spe- cies do not often fly, except oc- casionally when hard pressed to avoid capture. The front wings are longer and thicker than the “ hind wings, and are laid over the \ latter, which are thin and folded fanwise when not inuse. In these Fic. 52. The common house characters the roaches resemble ee eee the grasshoppers and katydids, young roaches and their family, the Blattidae, is usually placed with these insects in the order Orthoptera. The wings of insects are interesting objects to study. When spread out flat, as are those of the roach shown in Figure 53, they are seen to consist of a thin membranous tissue strengthened by many branching ribs, or veins, extending outward from the base. The wings seit insects are constructed on the same general plan and have the
[83 ]
INSECTS
same primary veins; but, since the great specialty of in- sects is flight, in their evolution they have concentrated on the wings, and the different groups have tried out different styles of venation, with the result that now each is distinguished by some particular pattern in the arrangement of the veins and their branches. The entomologist can thus not only distinguish by their wing structure the various orders of insects, as the Orthoptera, the dragonflies, the moths, the bees, and the flies, but in
Fic. 53. Wings of a cockroach, Periplaneta, showing the vein pattern characteristic of the roach family
many cases he can identify families and even genera. Particularly are the wings of value to the student of fossil insects, for the bodies are so poorly preserved in most cases that without the wings the paleontologist could have made little headway in the study of insects of the past. As it 1s, however, much is known of insects of former times, and a study of their fossil remains has con- tributed a great deal to our knowledge of this most versatile and widespread group of animals.
[ 84]
ROACHES AND OTHER ANCIENT INSECTS
The paleontological history of life on the earth shows us that the land has been inhabited successively by different forms of animals and plants. A particular group of creatures appears upon the scene, first in comparative insignificance; then it increases in Alene. in diversity of forms, and usually in the size of individuals, and may become the dominant form of life; then again it falls back to insignificance as its individuals decrease in size, its species in numbers, until perhaps its type becomes extinct. Meanwhile another group, representing another type of structure, comes into prominence, flourishes, and declines. It is a mistake, however, to get the impression that all forms of life have had this succession of up and down in their history, for there are many animals that have existed with little change for immense periods of time.
The history of insects gives us a good example of per- manence. The insects must have begun to be insects somewhere in those remote periods of time before the earliest known records of animals were preserved in the rocks. They must have been present during the age when the water swarmed with sharks and great armored fishes; they certainly flourished during the era when our coal beds were being deposited; they saw the rise of the huge amphibians and the great reptilian beasts, the Dinosaurus, the /chthyosaurus, the Plestosaurus, the Mosasaurus, ane all the rest of that monster tribe whose names are now familiar household words and whose bones are to be seen in all our museums. The insects were branching out into new forms during the time when birds had teeth and were being evolved from their reptile ancestors, and when the flowering plants were beginning to decorate the land- scape; they were present from the beginning of the age of mammals to its culmination in the great fur-bearing creatures but recently extinct; they attended the advent of man and have followed man’s whole evolution to the present time; they are with us yet—a vigorous race that
[85]
INSECTS
shows no sign of weakening or of decrease in numbers. Of all the land animals, the insects are the true blue-blood aristocrats by length of pedigree.
The first remains of insects known are found in the upper beds of the rocks laid down in the geological period of the earth’s history known as the Carboniferous. Dur-
Fic. 54. A group of common Carboniferous plants reaching the size and pro- portions of large trees. (From Chamberlin and Salisbury, drawn by Mildred Marvin from restorations of fossil specimens.) Courtesy of Henry Holt & Co.
Of the two large trees in the foreground, the one on the left is a Sigt//aria, that
on the right a Lepidodendron; of the two large central trees in the background
the left is a Cordaites, the right a tree fern; the tall stalks in the outermost circle are Calamites, plants related to our horsetail ferns
ing Carboniferous times much of the land along the shores of inland seas or lakes was marshy and supported great forests from which our coal deposits have been formed. But the Carboniferous landscape would have had a strange and curious look to us, accustomed as we
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ROACHES AND OTHER ANCIENT INSECTS
are to an abundance of hard-wood, leafy trees and shrubs, and a multitude of flowering plants. None of these forms of vegetation had yet appeared.
Much of the undergrowth of the Carboniferous swamps was composed of fernlike plants, many of which were, indeed, true ferns, and perhaps the ancestors of our modern brackens. Some of these ancient ferns grew to a great size, and rose above the rest in treelike forms, at- taining a height of sixty feet and more, to branch out in a feathery crown of huge spreading fronds. Another group of plants characteristic of the Carboniferous flora comprised the seed ferns, so named because, while closely resembling ferns in general appearance, they differed from true ferns in that they bore seeds instead of spores. The seed ferns were mostly small plants with delicate, ornate leaves, and they have left no descendants to modern times.
Along with the numerous ferns and seed ferns in the Carboniferous swamps, there were gigantic club mosses, or lycopods, which, ascending to a height sometimes of much more than a hundred feet, were the conspicuous big trees in the forests of their day (Fig. 54). These lycopods had long, cylindrical trunks covered with small scales arranged in regular spiral rows. Some had thick branch- ing limbs starting from the upper part of the trunk and closely beset with stiff, sharp-pointed leaves; others bore at the top of the trunk a great cluster of long slender leaves, giving them somewhat the aspect of a gigantic variety of our present-day yucca, or Spanish bayonet. The bases of the larger trees expanded to a diameter of three or four feet, and were supported on huge spreading underground branches from which issued the roots—a device, perhaps, that gave them an ample foundation in the soft mud of the swamps in which they grew.
The Carboniferous lycopods furnished most of our coal, and then, in later times, their places were taken by other types of vegetation. But their race is not yet extinct,
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INSECTS
for we have numerous representatives of them with us today in those lowly evergreen plants known as club mosses, whose spreading, much-branched limbs, usually trailing on the ground, are covered by rows of short, stiff leaves. The most familiar of the club mosses, though not a typical species, is the “ground pine.” This humble little shrub, so much sought for Christmas decoration, still in some places carpets our woods with its soft, broad, frondlike stems. In the fall when its rich dark green SO pleasingly contrasts with the somber tones of the season’s dying foliage, it seems to be an expression of the vitality that has preserved the lycopod race through the millions of years which have elapsed since the days of its great ancestors. The “‘resurrection plant,” often sold to housekeepers under false or exaggerated claims of a marvelous capacity for rejuvenation, is also a descendant of the proud lycopods of ancient times.
In our present woodlands, along the banks of streams or in other moist places, there grows also another plant that has been preserved to us from the Carboniferous forests—the common “‘horsetail fern,” or Eguisetum, that green, rough-ribbed stalk with the whorls of slender branches growing from its joints. Our equisetums are modest plants, seldom attaining a height of more than a few feet, though in South American countries some species may reach aa aleieude of thirty feet; but in Carboniferous times their ancestors grew to the stature of trees (Fig. 54) and measured their robust stalks with the trunks of the lycopods and giant ferns.
Aside from the numerous representatives of these sev- eral groups of plants, all more or less allied to the ferns, the Carboniferous forests contained another group of treelike plants, called Cordaites, from which the cycads of later times and our present-day maidenhair tree, or ginko, are probably descended. Then, too, there were a few representatives of a type that gave origin to our modern conifers.
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ROACHES AND OTHER ANCIENT INSECTS
It is probable that a visitor to those days of long ago might give us a more complete account of the vegetation that grew in the Carboniferous swamps than can be known from the records of the rocks, but the paleobotanist has a wealth of material now at hand sufficient to give us at least a pretty reliable picture of the setting in which the earliest of known insects lived and died.
And now, what were the insects like that inhabited the forests af those early times? Were they, too, strangely fashioned creatures, fit denizens of a far-off fairyland? No, nothing of the sort, at least not in appearance or structure, though “‘fit”’ ey probably were, from a physi- cal standpoint, for insects are fitted to live almost any- where. In short, the Carboniferous insects were prin- cipally roaches! Yes, those woods and swamps of millions of years ago were alive with roaches little different from our own familiar household pests, or from the numerous species that have not forsaken their native habitats for life in the cities.
Whoever looks to the geological records for evidence of the evolution of insects is sorely disappointed, for even in the venation of the wings those early roaches (Fig. 55) were almost identical with our present species (Big.263). As typical examples of the Carboniferous roaches, the species shown in Figure 55 serve well, and anyone can see, even though the specimens lack antennae and legs, that the creatures were just common roaches. Hence, we can easily picture these ancient roaches scut- tling up the tall trunks of the scaly lycopods, and shuffling in and out among the bases of the close-set leaf stems of the tree ferns, and we should expect to find an abundant infestation of them in the vegetational refuse matted on the ground. Insects of those days must have been com- paratively free from enemies, for birds did not yet exist, and all that host of parasitic insects that attack other insects were not evolved until more recent times.
Though by far the greater number of the Carboniferous
[ 89 ]
INSECES
insects known are roaches, or insects closely related to roaches, there were many other forms besides. Some of these are of particular interest to entomologists because, in some ways, they are more simple in structure than are
Fic. 55. Fossil cockroaches from Upper Carboniferous rocks
A, Asemoblatta mazona, found in Illinois, length of wing one inch. (From Handlirsch after Scudder.) B, Phyloblatta carbonaria, found in Germany. (From Handlirsch)
any of the modern insects, and in this respect they ap- parently stand closer to the hypothetical primitive insects than do any others that we know. And yet, the charac- ters by which these oldest known insects, called the Paleodictyoptera, ditter from modern forms are so slight that they would scarcely be noticed by anyone except an entomologist; to the casual observer, the Paleodic- tyoptera would be just insects. Their chief distinguish- ing marks are in the pattern of the wing venation, which is more symmetrical than in other winged insects, and, therefore, probably closer to that of the primitive ances- tors of all the winged insects. These ancient insects probably did not fold the wings over the back, as do most present-day insects, showing thus another primitive
[ go ]
ROACHES AND OTHER ANCIENT INSECTS
character, though not a distinctive one, since modern dragonflies (Fig. 58) and mayflies (Fig. 60) likewise keep the wings extended when at rest.
The question of how insects ‘acquired wings 1s always one of special interest, since, while we know perfectly well that the wing of a bird or of a bat is merely a modi- fied fore limb, the nature of the primitive organ from which the insect wing has been evolved is still a mystery. The Paleodictyoptera, however, may throw light upon the subject, for some of them had small flat lobes on the lateral edges of the back plate of the prothorax, which in fossil specimens look like undeveloped wings (Fig. 56). The presence of these prothoracic lobes, occurring as they do in some of the oldest known insects, has suggested the
Fic. 56. Examples of the earliest known fossil insects, called the Paleodic- tyoptera, having small lobes (a) projecting like wings from the prothorax
A, Stenodictya lobata (from Brongniart). B, Eudbleptus danielsi (drawn from
specimen in U. S. Nat. Mus.): Ti, T2, Ts, back plates of three thoracic segments
idea that the true wings were evolved from similar flaps of the mesothorax and metathorax. If so, we must pic- ture the immediate ancestors of the winged insects as creatures provided with a row of three flaps on each side of the body projecting stifly outward from the edges of the thoracic segments. Of course, the creatures could not actually fly with wings of this sort, but probably
[91]
INSEGES
they could glide through the air from the branches of one tree to another as well as can a modern flying squirrel by means of the folds of skin stretched along the sides of its body between the fore and the hind legs. If such lobes then became flexible at their bases, 1t required only a slight adjustment of the muscles already present in the body to give them motion in an up-and-down direction; and the wings of modern insects, in most cases, are still moved by a very simple mechanism which has involved the acquisition of few extra muscles.
It appears, however, that three pairs of fully-developed wings would be too many for mechanical efficiency. In the later evolution of insects, therefore, the prothoracic lobes were never developed beyond the glider stage, and in all modern insects this first pair of lobes has been lost. Furthermore, it was subsequently found that swift flight is best attained with a single pair of wings; and nearly all the more perfected insects of the present time have the hind pair of wings reduced in size and locked to the front pair to insure unity of action. The flies have carried this evolution toward a two-winged condition so far that they have practically achieved the goal, for with them the hind wings are so greatly reduced that they no longer have the form or function of organs of flight, and these insects, named the Diptera, or two- winged insects, fly with one highly specialized and efficient pair of wings (Fig. 167).
The Paleodictyoptera became extinct by the end of the Carboniferous period, and their disappearance gives added support to the idea that they were the last sur- vivors of an earlier type of insect. But they were by no means the primitive ancestors of insects, for, in the possession of wings alone, they show that they must have undergone a long evolution while wings were in the course of development; but of this stage in the history of insects we know nothing. The rocks, so far as has yet been revealed, contain no records of insect life below the upper
[92]
ROACHES AND OTHER ANCIENT INSECTS
beds of the Carboniferous deposits, when insects were already fully winged. This fact shows how cautious we must be in making negative statements concerning the extinct inhabitants of the earth, for we know that insects must have lived long before we have evidence of their existence. The absence of insect fossils earlier than the Carboniferous is hard to explain, because for millions of years the remains of other animals and plants had
Fic. 57. Machilis, a modern representative of ancient insects before the development of wings. (Length of body %» inch)
been preserved, and have since been found in compara- tive abundance. As a consequence, we have no concrete knowledge of insects before they became winged creatures evolved almost to their modern form.
At the present time there are wingless insects. Some of them show clearly that they are recent descendants from winged forms. Others suggest by their structure that their ancestors never had wings. Such as these, therefore, may have come down to us by a long line ee descent from the primitive wingless ancestors of all the insects. The common “fish moth,” known to entomolo- gists as Lepisma, and its near relation, Machi/is (Fig. 57), are familiar examples of the truly wingless insects of the present time, and if their remote ancestors were as fragile and as easily crushed as they, we may see a reason why they never left their i impressions in the rocks.
Along with the Carboniferous roaches and the Paleo- dictyoptera, there lived a few other kinds of insects, many of which are representative of certain modern
[93]
INSECTS
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[94 |
ROACHES AND OTHER ANCIENT INSECTS
groups. Among the latter were dragonflies, and some of these must have been of gigantic size, for insects, because they attained a wing expanse of fully two feet, while the largest of modern dragonflies do not measure more than eight inches across the expanded wings. But the length of wing of the extinct giant dragonflies does not necessarily mean that the bulk of the body was much greater than that of the largest insects living today. In general, the insects of the past were of ordinary size, the majority of them probably matching with insects of the present time.
The modern dragonflies (Fig. 58) are noted for their rapid flight and for the ability to make instantaneous changes in the direction of their course while flying. These qualities enable them to catch other insects on the wing, which constitute their food. Their wings are pro- vided with sets of special muscles, such as other insects do not possess, showing that the dragonflies are descended along a line of their own from their Carboniferous pro- genitors. They still retain a character of their ancestors in that they are unable to fold the wings flat over the back in the manner that most other insects fold their wings when they are not using them. The larger dragonflies hold the wings straight out from the sides of the body when at rest (Fig. 58); but a group of slender dragonflies, known as the damselflies (Plate 1, Fig. 2), bring the wings together over the back in a vertical plane.
The dragonflies are usually found most abundantly in the neighborhood of open bodies of water. Over the unobstructed surface of the water the larger species find a convenient hunting ground; but a more important reason for their association with water is that they lay their eggs either in the water or in the stems of plants growing in or beside it. The young dragonflies (Fig. 59) are aquatic and must have an easy access to water. They are homely, often positively ugly, creatures, having none of the elegance of their parents. They feed on other living creatures which their swimming powers enable
[95]
INSECUS
them to pursue, and which they capture by means of grasping hooks on the end of their extraordinarily long underlip (Fig. 134 A), which can be shot out in front of the head (B). The great swampy lakes of Paleozoic times must have furnished an ideal habitat for dragonflies, and it is probable that the most ancient dragonflies known had a structure and habits not very different from those of modern species.
Another very common insect of the present time, which appears ltkewise to be a direct descendant of Paleozoic ancestors, 1s the may- fly (Fig. 60). The young mayflies (Fig. 61) also live in the water, and are provided with gills for aquatic- breathing, having the form of flaps or filaments situated in a row along each side of the body. The adults (Fig. 60) are very delicate insects with four gauzy wings, and a pair of long threadlike tails projecting
Fis. gg. Ayounp dragons icOM) Cheereat end Gietite DodyaneG
fly, an aquatic creature the time of their transformation
that leaves the water only 5 5
when ready to transform they often issue in great swarms
into the adult (fig. 58) from the water, and they are par-
ticularly attracted to strong lights. For this reason large numbers of them come to the cities at night, and in the morning they may be seen sitting about on walls and windows, where they find themselves in a situation totally strange to their native habits and instincts. The mayflies do not fold their wings horizon- tally, but when at rest bring them together vertically over the back (Fig. 60). In this respect they, too, appear to preserve a character of their Paleozoic ancestors; though it must be observed that the highly evolved modern butterflies close their wings in the same fashion.
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BROACHES AND OTHER ANCIENT INSECTS
The roaches, the dragonflies, and the mayflies attest the great antiquity of insects, for since these forms ex- isted practically as they are today i in Paleozoic times, the primitive ancestors of all the insects, of which we have no remains in the geological records, must have lived in times vastly more remote. However, though we may search in vain the paleontological records for evidence of the origin and early development of insects, the sub- sequent evolution of the higher forms of modern insects is clearly shown by the species preserved in eras later
Fic. 60. A mayfly, representative of another order of primitive winged insects having numerous relations in Paleozoic times. (Twice natural size)
than the Carboniferous. Such insects as the beetles, the moths, the butterflies, the wasps, the bees, and the flies are entirely absent in the older rocks, but make their appearance at later periods or in comparatively recent times, thus confirming the idea derived from a study of their structure that they have been evolved from an- cestors more closely resembling the paleodictyopteran types of the Carboniferous beds.
The long line of descent of the roach, with almost no change of form or structure, furnishes material for a special lesson in evolution. If evolution has been a
[97]
INSECTS
matter of survival of the fittest, the roach, judged by survival, must be a most fit insect. Its fitness, however, is of a general nature; it is one that adapts the roach to live successfully in many kinds of conditions and circum- stances. Most other forms of mod- ern insects have been evolved through an adaptation to more special kinds of habitats and to particular ways of living or of feed- ing. Such insects we say are specialized, while those exemplified in the roach are said to be general- ized. Survival, therefore, may de- pend either on generalization or on specialization. Generalized forms of animals have a better chance of surviving through a series of chang- ing conditions than has an animal which is specifically adapted to one kind of life, though the latter may have an advantage as long as con- ditions are favorable to it.
The roaches, therefore, have sur- vived to present times, and will
Fic. 61. A young mayfly, : 5 Tae nbeee sk probably live as long as the earth is
ture. (One-half larger habitable, because, when driven
than natural size) : from one environment, they make
themselves at home in another; but we have all seen how the specialized mosquito disappears when its breeding places are destroyed. From this consideration we can draw some consolation for the human race, if we do not mind likening ourselves to roaches; for, as the roach, man is a versatile animal, capable of adapting himself to all conditions of living, and of thriving in extremes.
[98]
CHAPTER IV
WAYS AND MEANS OF LIVING
In our human society each individual must obtain the things necessary for existence; the manner by which he acquires them, whether by one trade or another, by this means or by that, does not physically matter so long as he provides himself and his family with food, clothing, and shelter. Exactly so it is with all forms of life. The physical demands of living matter make certain things necessary for the maintenance of life in that matter, but nature has no law specifying that any necessity shall be acquired in a certain manner. Life itself is a circum- scribed thing, but it has complete freedom of choice in the ways and means of living.
It is useless to attempt to make a definition of what living matter 1s, or of how it differs from non-living matter, for all definitions have failed to distinguish animate from non-animate substance. But we all know that living things are distinguishable from ordinary non-living things by the fact that they make some kind of response to changes in the contact between themselves and their environment. The “environment,” of course, must be broadly inter- preted. Biologically, it includes all things and forces that in any way touch upon living matter. Not only has every plant and animal as a whole its environment, but every part of it has an environment. The cells of an animal’s stomach, for example, have their environment in the blood and lymph on one side, the contents of the stomach on the other; in the energy of the nerves distributed to them; and in the effects of heat and cold that penetrate them.
[99]
INSECTS
The environmental conditions of the life of cells in a complex animal are too complicated for an elemental study; the elements of life and its basic necessities are bet- ter understood in a simple organism, or in a one-celled animal; but for purposes of description, it is most con- venient to speak of the properties of mere protoplasm. All the vital needs of the most highly organized animal are present in any part of the protoplasmic substance of which it is composed.
Protoplasm is a chemical substance, or group of sub- stances, the structure of which is very complex but 1s main- tained so long as there 1s no disturbance in the environ-
Fic. 62. Diagram showing the relation of the germ cells (GC/s) and the body cells (BC/s) in successive generations
A fertilized germ cell of generation A forms the germ cells and body cells of B,
a fertilized germ cell of B forms the germ cells and body cells of C, and so on.
The offspring C of B derives nothing from the body cells of the parent B, but both offspring C and parent B have a common origin in a germ cell of A
ment. Let some least thing happen, however, such as a change in the temperature, in the strength of the light, in the weight of pressure, or in the chemical composition of the surrounding medium, and the protoplasmic molecules, in the presence of oxygen, are likely to have the balance of their constituent particles upset, whereupon they partly decompose by the union of their less stable elements with oxygen to form simpler and more permanent compounds. The decomposition of the protoplasmic substances, like all processes of decomposition, liberates a certain amount of energy that had been stored in the making of the molecule, and this energy may manifest itself in various ways. If it
[| 100 }
WAYS AND MEANS OF LIVING
takes the form of a change of shape in the protoplasmic mass, Or movement, we say the mass exhibits signs of life. The state of being alive, however, is more truly shown if the act can be repeated, for the essential property of living matter is its power of reverting to its former chemical composition, and its ability thus gained of again reacting to another change in the environment. In restoring its lost elements, it must get these elements anew from the environment, for 1t can not take them back from the sub- stances that have been lost.
Here, expressed in its lowest terms, is the riddle of the physical basis of life and of the incentive to evolution in the forms of life. Not that these mysteries are any more easily understood for being thus analyzed, but they are more nearly comprehended. Being alive is maintaining the power of repeating an action; it involves sensitivity to stimuli, the constant presence of free oxygen, elimination of waste, and a supply of substances from which carbon, hydrogen, nitrogen, and oxygen, or other necessary ele- ments, are readily available for replacement purposes. Evolution results from the continual effort of living matter to perform its life processes in a more efficient manner, and the different groups of living things are the result of the different methods that life has tried and found advan- tageous for accomplishing its ends. Living organisms are machines that have become more and more complex in structure, but always for doing the same things.
If animals may be compared with machines in their physical mechanism, they are like them, too, in the fact that they wear out and are at last beyond repair. But here the simile ends, for when your car will no longer run, you must go to the dealer and order a new one. Nature provides continuous service by a much better scheme, for each organism is responsible for its own successor. This phase of life, the replacement of individuals, opens another subject involving ways and means, and it, likewise, can be understood best in its simpler manifestations.
[ ror |
INSECTS
The facts of reproduction in animals are not well ex- pressed by our name for them. Instead of “reproduc- tion,” it would be truer to say ‘‘repeated production,” for individuals do not literally reproduce themselves. Genera- tions are serially related, not each to the preceding; they follow one another as do the buds along the twig of a tree,
Fic. 63. The external structure of an insect
The body of a grasshopper dissected showing the head (H), the thorax (TA), and the abdomen (44). The head carries the eyes (Z), the antennae (4nt), and the mouth parts, which include the labrum (Zm), the mandibles (Md), the maxillae (Mx), and the labium (Ld). The thorax consists of three segments (7, 2, 3), the first separate and carrying the first legs (Zi), the other two com- bined and carrying the wings (42, 4#’s), and the second and third legs (Zz, Ls). The abdomen consists of a series of segments; that of the grasshopper has a large tympanal organ (7m), probably an ear, on each side of its base. The end of the abdomen carries the external organs of reproduction and egg-laying
and buds on the same twig are identical or nearly so, not because one produces the next, but because all are the result of the same generative forces in the twig. If the spaces of the twig between the buds were shortened until
[ 102 |
WAYS AND MEANS OF LIVING
one bud became contiguous with the one before, or became enveloped by it, a relation would be established between the two buds similar to that which exists between succes- sive generations of life forms. The so-called parent gen- eration, in other words, contains the germs of the succeeding generation, but it does not produce them. Each generation is simply the custodian of the germ cells entrust- ed to it, and the “‘off- spring” resembles the parent, wot because it is a chip off the parental block, but because both parent and offspring are developed from the same line of germ cells.
Parents create the conditions under which the germ cells will de- velop; they nourish and protect them during the period of their develop- ment; and, when each generation has_ served the purpose of its ex- istence, it sooner or later dies. But the in-
Fic. 64. The leg of a young grasshopper, showing the typical segmentation of an insect’s leg
The leg is supported on a pleural plate (Pl) in the lateral wall of its segment. The basal segment of the free part of the leg is the coxa (Cx), then comes a small trochanter (Jr), next a long femur (F) separated by the knee bend from the tibia (7), and lastly the foot, consisting of a sub-segmented tarsus (Tar), and a pair of terminal claws (C/) with an ad- hesive lobe between them
dividuals produced from its germ cells do the same for another set of germ cells produced simultaneously with themselves, and so on as long as the species persists.
To express the facts of succession in each specific form of animal, then, we should analyze each generation into germ cells and an accompanying mass of protective cells which
[ 103 ]
INSECTS
forms a body, or soma, the so-called parent. Both the body, or somatic, cells and the germ cells are formed from a single primary cell, which, of course, is usually produced by the union of two incomplete germ cells, a spermatozoon and an egg. The primary germ cell divides, the daughter cells divide, the cells of this division again divide, and the division continues indefinitely until a mass of cells 1s pro- duced. At a very early stage of division, however, two groups of cells are set apart, one representing the germ cells, the other the somatic cells. The former refrain from further development at this time; the latter proceed to build up the body of the parent. The relation of the somatic cells to the germ cells may be represented diagram- matically as in Figure 62, except that the usual dual par- entage and the union of germ cells is not expressed. The sexual form of reproduction is not necessary with all lower animals, nor with all generations of plants; in some insects the eggs can develop without fertilization.
The fully-developed mass of somatic cells, whose real function is that of a servant to the germ cells, has assumed such an importance, as public servants are prone to do, that we ordinarily think of it, the body, the active sentient animal, as the essential thing. This attitude on our part is natural, for we, ourselves, are highly organized masses of somatic cells. From a cosmic standpoint, however, no creature is important. Species of animals and plants exist because they have found ways and means of living that have allowed them to survive, but the physical universe cares nothing about them—the sunshine is not made for them, the winds are not tempered to suit their conven- ence. Life must accept what it finds and make the best of it, and the question of how best to further its own wel- fare is the problem that confronts every species.
The sciences of anatomy and physiology are a study of the methods by which the soma, or body, has contrived to meet the requirements imposed upon it by the unchanging laws of the physical universe. The methods adopted are as
[ 104 ]
WAYS AND MEANS OF LIVING
numerous as the species of plants and animals that have existed since life began. A treatise on entomology, there- fore, is an account of the ways and means of living that insects have adopted and perfected in their somatic organ- ization. Before discussing insects in particular, however, we must understand a little more fully the principal con- ditions of living that na- ture places on all forms of life.
As we have seen, life is a series of chemical re- actions in a_ particular kind of matter that can carry on these reactions. A “reaction” is an action; and every act of living matter involves a break- ing down of some of the substances in the proto- plasm, the discharging of the waste materials, and the acquisition of new materials to replace those lost. The reaction is in- herent in the physical or Fic. 65. Legs i Senay se showing
. . a special modi cations
chemical properties of A, outer surface of a hind leg, with a
protoplasmic compounds pollen basket on the tibia (74) loaded ea d h with pollen. B, a fore leg, showing the an epends upon the antenna cleaner (a) between the tibia and
substances with which the tarsus, and the long, hairy basal segment of the tarsus (7 Tar), which is
the protoplasm 1s Sur- used as a brush for cleaning the body rounded. It is the func-
tion of the creature’s mechanism to see that the con- ditions surrounding its living cells are right for the con- tinuance of the cell reactions. Each cell must be provided with the means of eliminating waste material and of restoring its lost material, since it can not utilize that which it has discarded.
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INSECTS
With the conditions of living granted, however, proto- plasm is still only potentially alive, for there is yet required a stimulus to set it into activity. The stimulus for life activities comes from changes in the physical forms of energy that surround or infringe upon the potentially living substance; for, “‘live’”’ matter, like all other matter, is subject to the law of inertia, which decrees that it must remain at rest until motion is imparted to it by other
Fic. 66. The head and mouth parts of a grasshopper
A, facial view of the head, showing the positions of the antennae (4nf), the
large compound eyes (Z), the simple eyes, or ocelli (OQ), the broad front lip,
or labrum (Lm) suspended from the cranium by the clypeus (C/p), and the bases of the mandibles (Ad, Md) closed behind the labrum
B, the mouth parts separated from the head in relative positions, seen from in front: HpAy, hypopharynx, or tongue, attached to base of labium; Lé, labium; Lm, labrum; Md, mandibles; Mx, maxillae
motion. A very small degree of stimulating energy, how- ever, may result in the release of a great quantity of stored energy
The food of all living matter must contain carbon, hydrogen, nitrogen, and oxygen. The mechanism of plants enables them to take these elements from com- pounds dissolved in the water of the soil. Animals must get them from other living things, or from the products of
{ 106 |
WAYS AND MEANS OF LIVING
living things. Therefore, animals principally have de- veloped the power of movement; they have acquired grasp- ing organs of some sort, a mouth, and an alimentary canal for holding the food when once obtained.
In the insects, the locomotory function is subserved by the legs and by the wings. Since all these organs, the three pairs of legs and the two pairs of wings, are carried by the thorax (Fig. 63, TA), this region of the body is distinctly the locomotor center of the insect. The legs (Fig. 64) are adapted, by modifications of structure in different species, for walking, running, leaping, digging, climbing, swim- ming, and for many varieties of each of these ways of pro- gression, fitting each species for its particular mode of living and of obtaining its food. The wings of insects are important accessions to their locomotory equipment, since they greatly increase their means of getting about, and thereby extend their range of feeding. The legs, fur- thermore, are often modified in special ways to perform some function accessory to feeding. The honeybee, as is well known, has pollen-collecting brushes on its front legs (Fig. 65 B), and pollen-carrying baskets on its hind legs (A). The mantis, which captures other insects and eats them alive, has its front legs made over into those efficient organs for grasping its prey and for holding the struggling victim which have already been described (Fig. 46).
The principal organs by which insects obtain and ma- nipulate their food consist of a set of appendages situated on the head in the neighborhood of the mouth, which, in their essential structure, are of the nature of the legs, for insects have no jaws comparable with those of vertebrate animals. The mouth appendages, or mouth parts as they are called, are very different in form in the various groups of insects that have different feeding habits, but in all cases they consist of the same fundamental pieces. Most important is a pair of jawlike appendages, known as the mandibles (Fig. 66 B, Ma), placed at the sides of the mouth (A, Ma), where they swing sidewise and close upon each other
[ 107 ]
INSECTS
below the mouth. Behind the mandibles is a pair of maxillae (B, Mx) of more complicated form, fitted rather for holding the food than for crushing it. Following the maxillae is a large under lip, or /abium (L4), having the
SoeGng VNC Int
Fic. 67. Lengthwise section of a grasshopper, showing the general location of the principal internal organs, except the respiratory tracheal system and the organs of reproduction
An, anus; Ant, antenna; Br, brain; Cr, crop; Ht, heart; Int, intestine; Mai, Malpighian tubules; Mrs, mouth; Oe, aesophagus; SeeGng, suboesophageal ganglion; Vent, stomach (ventriculus); “NC, ventral nerve cord; W, wings
structure of two maxillae united by their inner margins. A broad flap hangs downward before the mouth to form an upper lip, or /abrum (Lm). Between the mouth ap- pendages and attached to the front of the labium there is a large median lobe of the lower head wall behind the mouth, known as the Aypopharynx (Hphy).
Insects feed, some on solid foods, others on liquids, and their mouth parts are modified accordingly. So it comes about that, according to their feeding habits, insects may be separated i into two groups, which, like the fox and the stork, could not feed either at the table of the other. Those insects, such as the grasshoppers, the crickets, the beetles, and the caterpillars, that bite off pieces of food tissue and chew them, have the mandibles and the other mouth parts of the type described above. Insects that partake only of liquids, as do the plant lice, the cicadas, the moths, the butterflies, the mosquitoes and other flies, have the
[ 108 |
WAYS AND MEANS OF LIVING
mouth parts fitted for sucking, or for piercing and sucking. Some of the sucking types of mouth parts will be described in other chapters (Figs. 121, 163, 183), but it will be seen that all are merely adaptations of form based on the ordi- nary biting type of mouth appendages. The fossil records of the history of insects show that the sucking insects are the more recent products of evolution, since all the earlier kinds of insects, the cockroaches and their kin, have typical biting mouth parts.
The principal thing to observe concerning the organs of feeding, in a study of the physiological aspect of anatomy, is that they serve in all cases to pass the natural food materials from the outside of the animal into the alimen- tary canal, and to give them whatever crushing or masti- cation is necessary. It is within the alimentary canal, therefore, that the next steps toward the final nutrition of the animal take place.
The alimentary canal of most insects is a simple tube (Fig. 68), extending either straight through the body, or
Cx GC Vent AInt MInt Rect \ / us | / \ / / / | / San ss i i Sa —. — : ? : SSS es Ne Meh, = : ; =
Hphy Lb
Fic. 68. The alimentary canal of a grasshopper
Alnt, anterior intestine; 47, anus; Cr, crop; GC, gastric caeca, pouches of the
stomach; Hphy, hypopharynx (tongue); Lé, base of labium; Ma/, Malpighian
tubules; A¢7nt, mid-intestine; 44¢4, mouth; Oc, oesophagus; Rec/, hind intestine
(rectum); S/G/, salivary glands opening by their united ducts at base of hypo- pharynx; Vent, ventriculus (stomach)
making only a few turns or loops in its course. It con- sists of three principal parts, of which the middle part is the true stomach, or ventriculus (Vent) as it is called by insect anatomists. The first part of the tube includes a
[ 109 |
INSECTS
pharynx immediately behind the mouth, followed by a narrower, tubular oesophagus (Oe), after which comes a sac- like enlargement, or crop (Cr), in which the food is tem- porarily stored, and finally an antechamber to the stomach, named the proventriculus. The third part of the alimen- tary canal, connecting the stomach with the anal opening, is the intestine, usually composed of a narrow anterior part, anda wage posterior part, or rectum (Rect). Muscle layers surrounding the entire alimentary tube cause the food to be swallowed and to be passed along from one section to the next toward the rear exit.
With the taking of the food into the alimentary canal, the matter of nutrition is by no means accomplished, for the animal is still confronted with the problem of getting the nutrient materials into the inside of its body, where alone they can be used. The alimentary tube has no openings anywhere along its course into the body cavity. Whatever food substances the tissues of the animal receive, therefore, must be taken through the walls of the tube in which they are inclosed, ahd this transposition 1s accom- plished by dissolving them in a liquid. Most of the nutri- ent materials in the raw food matter, however, are not soluble in ordinary liquids; they must be changed chem- ically into a form that will dissolve. The process of get- ting the nutrient parts of the raw foodstuff into solution constitutes digestion.
The digestive liquids in insects are furnished mostly by the stomach walls or the walls of tubular glands that open into the stomach, but the secretion of a pair of large glands, called the salivary glands (Fig. 68, S/G/), which open between the mouth parts, perhaps has in some cases a digestive action on the food as it 1s taken into the mouth.
Digestion is a purely chemical process, but it must be a rapid one. Consequently the digestive juices contain not only substances that will transform the food materials into soluble compounds, but other substances that will
[110]
WAYS AND MEANS OF LIVING
speed up these reactions, for otherwise the animal would starve on a full stomach by reason of the slowness of its gastric service. The quickening substances of the diges- tive fluids are called enzymes, and each kind of enzyme acts on only one class of food material. An animal’s prac- tical digestive powers, therefore, depend entirely upon the specific enzymes its digestive liquids contain. Lacking this or that enzyme it can not digest the things that depend upon it, and usually its instincts are correlated with its enzymes so that it does not fill its stomach with food it can not digest. A few analyses of the digestive liquids of in- sects have been made, enough to show that their digestive processes depend upon the presence of the same enzymes as those of other animals, including man.
The grosser digestive substances, in cooperation with the enzymes, soon change all the parts of the food ma- terials in the stomach that the animal needs for its suste- nance into soluble compounds which are dissolved in the liquid part of the digestive secretions. Thus is produced a rich, nutrient juice within the alimentary canal which can be absorbed through the walls of the stomach and intes- tine and can so enter the closed cavity of the body. The next problem is that of distribution, for still the food ma- terials must reach the individual cells of the tissues that compose the animal.
The insect’s way of feeding, of digesting its food, and of absorbing it is not essentially different from that of the higher animals, including ourselves, for alimentation 1s a very old and fundamental function of all animals. Its means of distributing the digested food within its body, however, is quite different from that of vertebrates. The absorbed pabulum, instead of being received into a set of lymphatic vessels and from these sent into blood-filled tubes to be pumped to all parts of the organism, goes directly from the alimentary walls into the general body cavity, which is filled with a liquid that bathes the inner surfaces of all the body tissues. This body liquid 1s called
brri
INSECTS
the “blood” of the insect, but it is a colorless or slightly yellow-tinted lymph. It is kept in motion, however, by a
vy V
Fic. 69. Diagram of the typical structure of an insect’s heart and supporting dia- phragm, with the course of the circulating blood marked by
arrows
Ao, aorta, or anterior tubular part of the heart without lateral openings; Dph, mem- branous diaphragm; Ht, ante- rior three chambers of the heart, which usually extends to the posterior end of the body; Mc/, muscles of dia- phragm, the fibers spreading from the body wall to the heart; Ost, ostium, or oneof the lateral openings into the heart chambers
pulsating vessel, or heart, lying in the dorsal part of the body; and by this means the food, now dissolved in the body liquid, 1s carried into the spaces between the various organs, where the cells of the latter can have access to it.
The heart of the insect 1s a slender tube suspended along the midline of the back close to the dorsal wall of the body (Fig. 67, Ht). It has intake apertures along its sides (Fig. 69, Ost), and its anterior end opens into the body cavity. It pulsates - for- ward, by means of muscle fibers in its walls, thereby sucking the blood in through the lateral openings and discharging it by way of the front exit. An im- perfect circulation of the blood is thus established through the spaces between the organs of the body cavity, sufficient for the purposes of so small an animal as an insect.
The final act of nutrition comes now when the blood, charged with the nutrient materials ab- sorbed from the digested food in the alimentary canal, brings these materials into contact with the inner tissues. The tissue cells, by the inherent power of
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all living matter (which depends on the laws of osmosis and on chemical affinity), take for themselves whatever they need from the menu offered by the blood, and with this matter they build up their own substance. It is evident, therefore, that the blood must contain a sufh- cient quantity and variety of dietary elements to satisfy all possible cell appetites; that the stomach’s walls and their associated glands must furnish the enzymes appro- priate for making the necessary elements available from the raw food matter in the stomach; and, finally, that it must be a part of the instincts of each animal species to consume such native foodstuffs of its environment as will supply every variety of nourishing elements that the cells demand.
As we have seen, the demand for food comes from the loss of materials that are decomposed in the tissues during cell activity. Better stated, perhaps, the chemical break- down within the cell is the cause of the cell activity, or is the cell activity itself. The way in which the activity is expressed does not matter; whether by the contraction of a muscle cell, the secretion of a gland cell, the generation of nerve energy by a nerve cell, or just the minimum activity that maintains life, the result is the same always—the loss of certain Substances: But, as with most chemical reduc- tion processes, the protoplasmic activity depends upon the presence of available oxygen; for the decomposition of the unstable substances of the protoplasm is the result of the affinity of some of their elements for oxygen. Conse- quently, when the stimulus for action comes over a nerve from a nerve center, a sudden reorganization takes place between these protoplasmic elements and the oxygen atoms which results in the formation of water, carbon dioxide, and various stable nitrogenous compounds.
The substances discarded as a result of the cell activi- ties are waste products, and must be eliminated from the organism for their presence would clog the further activity of the cells or would be poisonous to them. The animal,
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therefore, must have, in addition to its mechanisms for bringing food and oxygen