Insects, Their Ways and Means of Living/Chapter I

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Insects

Their Ways and Means of Living

________


Chapter I

The Grasshopper


Sometime in spring, earlier or later according to the latitude or the season, the fields, the lawns, the gardens, suddenly 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 involved 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 spontaneously from matter in the earth; the public would believe him, and thereafter would countenance no contrary 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.


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 observes 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 he can closely watch the hatching and observe with accuracy 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.

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Fig 1. Young grasshoppers

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 “grasshopper.” 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 out popular natural history parlance we 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 establish a better state of nomenclatural affairs by creating a set of international names for all living things, but since

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Fig 2. The end of the body of a male and a female grasshopper
The body, or abdomen, of a male (A) is bluntly rounded; that of the female (B) bears two pairs of thick prongs, which constitute the egg-laying organ, or ovipositor (Ovp)

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 Frontispiece). A similar insect 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 examine a few specimens of locusts, which we will proceed to call grasshoppers, you may observe 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 provisions of nature that whatever any creature is compelled by its instinct to do, for the doing of that thing it is provided with appropriate tools. Its tools, however, unless it is a human animal, are alwavs 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

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Fig 3. The 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 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

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Fig. 4. Egg pods of a grasshopper, showing various shapes: one opened exposing the eggs within. (Much enlarged)

substance from the body of the insect is discharged over them. This substance 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 is fresh and sticky, particles of earth adhere and make a 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 haphazard. 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.

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Fig. 5. Eggs of a grasshopper; one split at the upper end, showing the young grasshopper about to emerge

The ends of the eggs are rounded or bluntly 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, which may be almost straight.The surface is smooth and lustrous to the naked eye, but under the microscope it is 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 circumstances. 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.

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 development 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 created, will not hatch at all, the embryos within them math a certain stage of development and there they stop, and most of them never will resume their growth unless they are subjected 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 most conclude that it is not a whim, but a useful physiological property 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 development, might hatch that same season if mild weather should continue. And then, what chance would the poor fledgling have when a delayed winter conies 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 sonable hatching. There are, however, species not thus insured, 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.

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Fig. 6. Young grasshopper emerging from its eggshell

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 hatching, the outer coat splits open in an irregular 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 glistening capsule, through the semitransparent walls of which the little grasshopper inside 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 the young grasshopper emerges by slowly 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 sort 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, liberates itself from the shriveled remnant of its hatching skin, and becornes a free new creature in the world. Being a grasshopper, it proceeds to jump, and with its first efforts clears a distance of four or five inches, sornething 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 burrowing upward until they come out at the surface of the ground. Of course, they are not very far beneath the surface, and most of the way will be through the easily penetrated 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 entomologists 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, pressing 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 is 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 mechanism that propels it through the earth? And finally, 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 solution 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

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Fig. 7. Eggs of a species of katydid attached to a twig; young insect in the successive stages of emerging from an egg; and the newly-hatched young

produce results depending on the construction of the mechanism. So the effects 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 conception of the nature of instinct; it is sufficient to say that something in the surroundings encountered by the newly-hatched grasshopper, or some substance generated within it, sets its nerve energy into action, that the nerve energy working on a definite mechanism produces the motions of the insect, and that the 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 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 to emerge. The latter is inclosed in a delicate transparent sheath, within which its long legs and antennae 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 overbalance 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 creature. 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 insected between the thorax and abdomen, the grasshopper, like the fly and the wasp and all other insects, consists of a 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 insects 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

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Fig. 8. A young grasshopper, or nymph, in the second stage after hatching

body sections are called segments, and all insects and their relatives, including the centipedes, the shrimps, lobsters, and crabs, and the scorpions and spiders, are segmented animals. The insect'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, Ant), 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 appendages 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 is segmented, and each pair of its appendages is borne by a single segment, but the head segments are later condensed into the solid capsule of the cranium. Thus we see that the entire body of an insect is composed of a series of segments which have become grouped into the three body

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Fig. The metamorphosis of a grasshopper, Melanoplus atlanus, showing its six stages of development from the newly-hatched nymph to the fully-winged adult. (Twice natural size)

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 be described in another chapter treating of the internal organization (page 114).

Most young insects grow rapidly because 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 mature growth of the form in which they leave the egg, for, as we shall see, many insects complicate their lives by having several different stages, in each of which they present quite a different form. The grasshopper, however, is an insect that grows by a direct course from its form at hatching to that of the adult, and at all stages it is recognizable as a grasshopper (Fig. 9). A young moth, on the other hand, hatching in the 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 metamorphosis. There are different degrees of such transformation; 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 outside 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 confronted 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 expedlency, and periodically molts. 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 grasshopper emerges from it, carefully pulling its legs and antennae 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 shedding 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, accompanied 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, W3), 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 something 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 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 expanding and lengthening wings, which can now hang downward 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 that reach to the tip of the body. This rapid growth is explained 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 is important to understand the process of molting as it takes place in the grasshopper, because the processes of metamorphosis, such as those which accomplish the transformation 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 is 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 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 observer then gets the impression that he is witnessing a sudden 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 produced 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 is 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 obscurity and enduring impotency as individuals, the grasshopper 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 entomologists to investigate them. This was in the years following the Civil War, when, for some reason, the locusts that normaily 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 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 entornologists of the investigating commission in the vear 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 swarrn in the air was described as being like that of “a vast body 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 commission, Dr. C. V. Riley, who bas 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 Iocust-swarms have fallen upon the land. The morrow comes, and, ah! what a change it brings! The fertile land of promise and plenty has hecome a desolate waste, and old Sol, even at his hightest, 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 is that of driving 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 effective method of killing the pests is that of poisoning them. A mixture is 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. E. O. G. Kelly, who has given us a 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

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Fig. 10. A fly whose larvae are parasitic on grasshoppers, Sarcophaga kellyi. (Much enlarged)

to dart after grasshoppers on the wing and strike against them. The stricken insect at once drops to the ground. Examination reveals no physical injury to the victim, but on a close inspection there may be found adhering to the under 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 foids 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 grasshopper. 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 sort, flexible body (Fig. 182 D).

In form, the young Sarcophaga kellyi does not differ particularly 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 iaying 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 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 tender 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, however, the grasshopper bas 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 is destroyed that another may live.

ls the Sarcophaga kellyi a creature of uncanny shrewdness, an ingenious 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 progeny 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, to which 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 foresight, but on some mechanical action of the nervous system, 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 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-looking individuals that could not be mistaken on sight, but

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Fig 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 without suspicion in the crowd. And thus it is with the insects, 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 neighbor. Here, for example, in the same field with the grasshoppers, 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 are known as "blister beetles" because they have a substance 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 triungulins 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 reading,

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Fig. 12. The first-stage larva, or “triungulin,” of the striped blister beetle (fig. 11 B). Enlarged 12 times.
(From Riley)

and the following account is taken, with a few omissions, from the history of Epicauta vittata as given by Dr. C. V. Riley:

From July till the middle of October the eggs are being laid in the ground in loose, irregular 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 intervals, producing in the aggregate probably from four to five hundred ova. She prefers for purposes of oviposition the very same warm sunny locations chosen by the locusts, and doubtless instinctively places ner eggs near those of these last, as I have on several occasions found them in close proximity. In the course of about 10 days—more or less according to the temperature of the ground—the first larva or triungulin hatches. These little triungulins (Fig. 12), at first feeble and perfectly 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 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 bas 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 triungulins 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

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Fig. 13. The second-stage larva of the striped blister beetle.
(Frorn Riley)

from its feeding and enters a period of rest. Soon the skin plits along the back, and the creature issues in the second stage of its existence. Very curiously, it is 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 fourth molt, however, it quits the eggs and burrows a short distance into the soil, where it composes itself for a period of retirement, and here undergoes another molt, in which the skin is not cast off. 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 it changes to a pupa, the stage in which it is to be transformed 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 triungulins, 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 in numbers. 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.