INSECTS NEVER GROW.

BY S. S. RATHVON.

Many fancy that a little fly is only little because it is young, and that it will grow up in process of time to be as big as a blue-bottle. Now this is entirely wrong, for when an insect has once attained to its winged state it grows no more. All the growing, and most part of the eating, is done in its previous state of life, and indeed there are many insects, such as the silk worm moth, which do not eat at all from the time that they assume the chrysalis state to the time they die.-Church Union.

"That's so❞—and yet it is only so in a qualified sense, for there are some insects that never attain to a winged state; that is, they are either totally wingless, or are so seldom seen in that state that most persons never know otherwise than that they are wingless always. Especially is this the case with ants, fleas, spring-tails, and the females of some bugs, grasshoppers, crickets, beetles, moths, flies, and all lice, as well as many others. Although it is not strictly true that "insects never grow," yet it is true that they never grow after that stage of development when the large body of the insect world attained to a winged state; but there are some orders of insects to which the rule may be applied almost universally. There is nothing that is more likely to leave a false impression upon the minds of the superficial on this subject than the appearance that insects do grow without any qualification whatever. Indeed we often meet persons. thoroughly informed on many other subjects, who suppose that the different sizes in insects, of apparently the same kinds, are indications of different ages. Practically there are four more or less directly marked periods in the life of insects, and are the ova, or egg state; the larva, or worm state; the pupa, or intermediate state, and imago, or adult state; and in one or the other of these states the species are perpetuated, or carried over from one season to another. In beetles, butterflies, moths, bees, wasps, hornets, flies, dragon-flies, and some, these states, as a general rule, are very distinctly marked; but they are not so in bugs, cockroaches, locusts, earwings, grasshoppers, treehoppers, crickets, and a number of others. In this latitude, perhaps, the one particular species, (except the common house-fly,) which impresses itself earliest and the most indelibly upon the minds of youth or adult age, is the common "tumble-bug" or "tumbledung," from its habits of forming a ball out of animal excretions, and rolling it for some distance before burying it in the earth. This is the Canthon lævis of entomologists, although there are various species of them.

Now from more than fifty years ago, when we made the first observation, down to five and thirty years ago, we were under the impression that the various sizes of these insects, found in the droppings of cattle, were the young and the old of the same species. For had we not over and over again deprived the industrious and persevering owners of these balls, opened them, and found therein a small black beetle, approximating in form to the former possessors of the ball, and what else, we thought, could they possibly be if they were not their legitimate offspring? These little black beetles, we subsequently learned, were not only different species, but belonged to different genera, Aphodius, Onthophagus and others. Nor did the fact that we sometimes found within these balls little beetles that were not entirely black-the hinder half of the body being mottled with clay yellow-astonish us any more than that we should occasionally see a robin, a catbird, or a mouse, that was altogether or nearly white.

But since then it has been demonstrated to us a thousand times, clear as the light of the living day, that these beetles do not grow or acquire any new beauty after they have assumed the beetle form-nor any other species belonging to the same order-and that all the different sizes indicate different species, or varieties of the same species. The eggs, however, of some insects do very perceptibly increase in size, and the larva or grub grows, and sometimes grows very rapidly, in all of them. But there is as much difference in the size of the larva as there is in the size of the beetles into which they are subsequently transformed. As a general thing the mature beetles, if they feed on anything at all, it is on a different substance from which the larva fed upon. We may except the carniverous species, and some of the CHRYSOMELANS-the "Colorado potato beetles," the "Tortoise beetles," &c., &c., for instance; under any circumstances, however, it is while they are in the larva state that they increase in size, or grow, and it is during that state that the destructive kinds are the most destructive. Like active and hungry boys, they are always hungry and can always eat. Indeed, childhood and youth may be appropriately regarded as the larval period of manhood, and the future perfection of the insect depends as much upon a plentiful supply of healthy food as the physical perfection of manhood depends upon proper food and physical training whilst in the boy state. During the pupa or intermediate state, beetles eat nothing. Some eat nothing, or next to nothing, in the imago state; but others eat fruit, foliage, pollen, flowers, and the predaceous kinds feed on carrion or other small insects, grubs, water animals, or fishes, &c., &c.

The larva of butterflies and moths, which are known under the names of caterpillars, cut-worms, sphinxes, or,simply worms, all grow; and in many instances grow very rapidly; and during that period feed very ravenously, eating their own bulk and weight in a single day; but after they have

assumed the butterfly and moth forms they never grow any. They not only do not grow, but they acquire no new beauties, but rather lose their origi nal beauty the older they get, and we often see them awkwardly flitting about in faded and tattered garments, dilapidated caricatures of their former selves. The best specimens obtained by entomologists, are those which are bred under their own personal supervision. Therefore, all the different sizes of these insects we see, are indications of different species, except, as before stated, the different varieties or sizes in the same species, which may have been caused by contingencies beyond the control of the insects, such as stinted food, inferior quality of the food, or unfriendly weather and surroundings. In no other order of insects, universally considered, is there a more marked distinction in form and habits-between the larva, the pupa, and the imago- than there is in that which includes the butterflies and moths. The larvae are masticating animals, the pupa are quiescent and fixed, and the image are suctorial in their feeding habits.

In the order Diptera, or two-winged flies, the case is the same, that is, they do not grow after they have assumed the form of a fly, notwithstanding the great variety in the sizes of the masses that are sometimes found congregated together, may appear as if they were young and old, but it is only an appearance, for, in reality, the smallest fly may happen to be the oldest, and vice versa. It is the same in others mentioned and unmentioned, after they have acquired wings, namely, they do not grow. It will be remembered that in the foregoing the larvæ are excluded from the eggs in the form of grubs, worms, caterpillars, maggots, &c., some entirely footless, and others having from six to twenty-two feet; but in those which follow, the larva come from the eggs in form of the mature insects-or nearly so lacking only the wings; having the usual six feet, the mandibulated or suctorial mouths the same, in all their states of transition, and feed throughout the entire periods of their lives; and consequently have no quiescent period, but are as active and destructive in one state as they are in the other. In these it may appear to the novice that insects do grow, from the fact that he may not be able to distinguish between larva, pupa and imago, but even in these they do not grow after they get wings, although some of them never attain those appendages, whether they are males or females, or whether they are old or young.

Grasshoppers (true,) locusts and crickets, for instance, have the same number and the same formed limbs when young they ever have, and can hop from the moment they leave the eggs. This is the same in regard to the true bugs, the tree-hoppers, the false locusts, and approximately many others that do not hop. Therefore, to say that "insects do not grow," without any qualification whatever, would not be credited by those who may have the demonstration before their eyes daily, that they do grow; so