BORING-CATERPILLARS. GLAUCOPIDIANS. MOTHS. SPINNERS. LITHOERMINE-MOTHS. TUSSOCK-MOTHS. LACKEY SIANS. TIGER-MOTHS. MOTHS.-LAPPET-MOTHS.-SATURNIANS.-CERATOCAMPIANS. CARPENTERCUT-WORMS. DELTA-MOTHS. - MOTHS - PSYCHIANS. NOTODONTIANS. OWL-MOTHS. HERE are perhaps no insects which are so commonly and so universally destructive as caterpillars; they are inferior only to locusts in voracity, and equal or exceed them in their powers of increase, and in general are far more widely spread over vegetation. Caterpillars are the young of butterflies and of moths; and of these, five hundred species, which are natives of Massachusetts, are already known to me, and probably there are at least as many more kinds to be discovered within the limits of this Commonwealth.1 As each female usually lays from two hundred to five hundred eggs, one thousand different kinds of butterflies and moths will produce, on an average, three hundred thousand caterpillars; if one half of this number, when arrived at [1 The number of species in the United States may fairly be estimated at 3,500, or even more. My Catalogue, published by the Smithsonian Institute, contains the names of nearly 1,800 already described by various authors, exclusive of Microlepidoptera, which is a numerous family of itself, and comparatively little progress has as yet been made in the discovery of our indigenous species generally. The latest and most complete work on German and Swiss Lepidoptera (Die Schmetterlinge Deutschlands und der Schweiz, von H. v. Heinemann, Brunswick, 1859) gives 1,387 species, exclusive of Microlepidoptera, in those two countries alone, and we can confidently reckon on finding over three times that number in the United States. - MORRIS.] maturity, are females, they will give forty-five millions of caterpillars in the second, and six thousand seven hundred and fifty millions in the third generation. These data suffice to show that the actual number of these insects, existing at any one time, must be far beyond the limits of calculation. The greater part of caterpillars subsist on vegetable food, and especially on the leaves of plants; hence their injuries to vegetation are immense, and are too often forced upon our notice. Some devour the solid wood of trees, some live only in the pith of plants, and some confine themselves to grains and seeds. Certain species attack our woollens and furs, thereby doing us much injury; even leather, meat, wax, flour, and lard afford nourishment to particular kinds of caterpillars. Caterpillars vary greatly in form and appearance, but, in general, their bodies are more or less cylindrical, and 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 eyes2 on each side of the head, two short antennæ, 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 [2 Though Dr. Harris mentions the "eyes" of caterpillars, yet be it understood, he does not assert that they see. It is very doubtful whether they have the faculty of vision. - MORRIS.] 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 early 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. Other caterpillars suspend themselves, in various ways, by silken threads, without enclosing their bodies in cocoons; and again, there are others which merely enter the earth to undergo their transformations. 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 till 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, however, there may be found traces of a head, tongue, antennæ, wings, and legs, closely pressed to the body, to which these parts are cemented by a kind of varnish. Some chrysalids 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. After 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, antennæ, 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 shrivelled; 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 conversion 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 antennæ 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 slender tongue, by means of which liquid nourishment is conveyed to the mouth of the insect, and its stomach becomes capable of digesting only water and the honeyed juice of flowers. Ceasing to increase in size, and destined to live but a short time after their final transformation, butterflies and moths spend this brief period of their existence in flitting from flower to flower and regaling themselves with their sweets, or in slaking 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. |