CATERPILLAR. Caterpillars are the young or larvae of butterflies and moths, and being all vegetable eaters and extremely voracious, inferior only to locusts and grasshoppers, may be classed as among the most destructive of insects to vegetation. They are found everywhere, in every climate where vegetation exists, and are exceedingly fecund. The females lay from 200 to 500 eggs each, so that of the nearly 4,000 species enumerated, as belonging to the United States, their numbers in prolific seasons are almost beyond calculation. Caterpillars exist in a great variety of forms, from almost microscopic ones up to the immense tobacco and tomato worm. We give cuts of two smooth and two hairy species, which will serve for illustration. Dr. Harris, in Insects Injurious to Vegetation, defines caterpillars as follows: Caterpillars vary greatly in form and appearance, but in general, their bodies are more or less cylindrical, and are composed of twelve rings or segments, with a shelly head, and from ten to sixteen legs. The first three pairs of legs are covered with a shelly skin, are jointed and tapering, and are armed at the end with a little claw; the other legs are thick 'and fleshy, without joints, but elastic or contractile, and are generally surrounded at the extremity by numerous minute hooks. There are six very small eyes on each side of the bead, two short antennae, and strong jaws or nippers. placed at the sides of the mouth, so as to open and shut sidewise. In the middle of the lower lip is a little conical tube, from which the insects spin the silken threads that are used by them in making their nests and their cocoons, and in various other purposes of their economy. Two long and slender bags, in the interior of their bodies, and ending in the spinning tube, contain the matter of the silk. This is a sticky fluid, and it flows from the spinner in a fine stream, which hardens into a thread so soon as it comes to the air. Some caterpillars make but very little silk ; others, such as the silk-worm and the apple-tree caterpillar, produce it in great abundance. Some caterpillars herd together in great numbers, and pass the entire period of their existence in society; and of these there are species which unite in their labors, and construct tents serving as a common habitation in which they live, or to which they retire occasionally for shelter. Others pass their lives in solitude, either exposed to the light and air, or sheltered in leaves folded over their bodies, or form for themselves silken sheaths, which are either fixed or portable. Some make their abodes in the stems of plants, or mine in the pulpy substance of leaves; and others conceal themselves in the ground, from which they issue only when in search of food.
Caterpillars usually change their skins about four times before they come to their growth At length they leave off eating entirely, and prepare for their first transformation. Most of them, at this period, spin around their bodies a sort of shroud or cocoon, into which some interweave the hairs of their own bodies, and some employ, in the same way, leaves, bits of wood, or even grains of earth. Still other species of our caterpillars suspend themselves, in various ways, by silken threads, without enclosing their bodies in cocoons; and, again, there are species which merely enter the earth to undergo their transform ations. When the caterpillar has thus prepared itself for the approaching change, by repeated exertions and struggles, it bursts open the skin on the top of its back, withdraws the fore part of its body, and works the skin backwards until the hinder extremity is extricated. It then no longer appears in the caterpillar form, but has become a pupa or chrysalis, shorter than the caterpillar, and at first sight apparently without a head or limbs. On close examination, how ever, there may be found traces of a bead, tongue, antennae, wings and legs, closely press ed to the body, to which these parts are cement ed by a kind of varnish. Some chrysalides are angular, or furnished with little protuberances; but most of them are smooth, rounded at one end, and tapering at the other extremity. While in the pupa state these insects take no food, and remain perfectly at rest, or only move the hinder extremity of the body when touched. ,A her a while, however, the chrysalis begins to swell and contract, till the skin is rent over the back, and from the fissure there issues the head, antennae, and body of a butterfly or moth. When it first emerges from its pupa-skin the insect is soft, moist ,and weak, and its wings are small and shriveled; soon, however, the wings stretch out to their full dimensions, the superfluous moisture of the body, passes off, and the limbs acquire their proper firmness and elasticity. The con
version of a caterpillar to a moth or butterfly is a transformation of the most complete kind. The form of the body is altered, some of the legs disappear, the others and the antennae become much longer than before, and four wings are acquired. Moreover, the mouth and digestive organs undergo a total change; for the insect, after its final transformation, is no longer fitted to subsist upon the same gross aliment as it did in the caterpillar state; its powerful jaws have disappeared, and instead thereof we find a slen der tongue, by means of which liquid nourish ment is conveyed to the mouth of the insect, and its stom ach becomes capable of digesting only water and the honeyed juice of flowers. Ceas ing to increase in size, and destined to live but a short time after their final transformation, but terflies and moths spend this brief period of their existence in flitting from flower to flower and regaling themselves with their sweets, or in slak ing their thirst with dew, or with the water left standing in puddles after showers, in pairing with their mates, and in laying their eggs; after which they die a natural death, or fall a prey to their numerous enemies. These insects belong to an order called Lepidoptera, which means scaly wings; for the mealy powder with which their wings are covered, when seen under a pow erful microscope, is found to consist of little .scales, lapping over each other like the scales of fishes, and implanted into the skin of the wings by short stems. The body of these insects is also more or less covered with the same kind of scales, together with hair or down in some species. The tongue consists of two tubular threads placed side by side, and thus forming an instrument for suction, which, when not in use, is rolled up spirally beneath the head, and is more or less covered and concealed on each side by a little scaly or hairy-jointed feeler. The shoulders, or wing-joints, of the fore wings are covered, on each side, by a small triangular piece, forming a kind of epaulette, or shoulder cover; and between the head and the thorax is a narrow piece, clothed with scales or hairs, slop ing backwards, which may be called the collar. The wings have a few branching veins, generally forming one or two large meshes on the middle. The legs are six in number, though only four are used in walking by some butterflies, in which the first pair are very short, and are folded like a tippet. on the breast; and the feet are five-jointed, and are terminated, each, by a pair.of claws. It would be difficult and, indeed, impossible to arrange the lepidopterous insects according to their forms, appearance and• habits, in the cater pillar state, because the caterpillars of many of them are as yet unknown ; and therefore it is found expedient to classify them mostly accord ing to the characters furnished by them in the winged state. We may first divide the Lep ; clop tera into three great sections, called butterflies, hawk-moths, and moths, corresponding to the general Papaw, Sphinx, and Phabence of Lin naus. The butterflies (Papiliones) have thread like antenna, which are knobbed at the end ; the fore wings in some, and all the wings in the greater number, are elevated perpendicularly, and turned back to back, when at rest; they have generally two little spurs on the hind legs, and they fly by day only. The hawk-moths (Sphinges) generally have the antenna thickened in the middle and tapering at each end, and most often hooked at the tip; the wings are narrow in proportion to their length, and are confined together by a bristle or bunch of stiff hairs on the shoulder of each hind wing, which is retained by a corresponding hook on the under side of each fore wing; all the wings, when at rest, are inore or less inclined like a roof, the upper ones covering the lower wings; and there are two pairs of spurs on the hind legs. A few fly by day, but the greater number in the morning and evening twilight. In the moths (Phaleence) the anten na are neither knobbed at the end nor thickened in the middle, but taper from the base to the extremity, and are either naked, like a bristle, or are feathered on each side; the wings are con fined together by bristles and hooks, the first pair covering the hind wings, and are more or less sloping when at rest; and there are two pairs of spurs to the hind legs. These insects fly mostly by night.