LA RVA, in natural history. The larva state of insects, in general, denotes cater pillars of all kinds. The caterpillar state is that through which every butterfly must pass betbre it arrives at its perfec and beauty.
The change from caterpillar to butter fly was long esteemed a sort of meta morphosis, or real change of one animal into another ; but this is by no means the case. The insects of the genus ichneu mon contributed much to establish and perpetuate such absurd notions, in former naturalists. These insects are parasites, and deposit their eggs in the bodies of the larvae of butterflies, moths, &c. The young proceeding from those eggs nourish themselves at the expense of the cater pillar, by feeding upon those parts which are not immediately vital. The caterpil lar is at length killed, and the perfect ichneumon comes forth, much to the sur prise or the observer, who, anticipating a different result, viewed it as an instance of equivocal generation. But the more ac curate observations of modern naturalists have shown, that the egg of a butterfly produces a butterfly, with all the linea ments of its parent; only these are not disclosed at first, but for the greater part of the animal's life they are covered with a sort of case or muscular coat, in which are legs for walking: these only suit it in this state, but its mouth takes in nourish ment, which is conveyed to the included animal; and after a proper time this covering is thrown off, and the butterfly, which all the while might be discovered in it by an accurate observer, with the help of a microscope, appears in its pro. per form. The care of all the butterfly tribe to lodge their eggs in safety is sur prising. Those whose eggs are to be hatched in a few weeks, and who are to live in the caterpillar state during part of the remaining simmer, always lay them on the leaves of such plants as will afford a proper nourishment ; but, on the con trary, those whose eggs arc to remain un hatched till the fidlowing spring, always lay them on the branches of trees and shrubs, and usually are careful to select such places as are least exposed to the rigour of the ensuing season, and fre quently cover them from it in an artful manner. Some make a general coat of a hairy matter over them, aking the hairs from their own bodies for that purpose ; others hide themselves in hollow places, in trees, and in other sheltered cells, and there live in a kind of torpid state during the whole winter, that they may deposit their eggs in the succeeding springs at 'a time when there will be no severities of weather for them to combat. The day butterflies only do this, and of these but a very few species : but the night ones, or phalemr, all, without exception, lay their eggs as soon as they have been in copulation with the male, and die imme diately afterwards.
Nothing is more surprising in insects than their industry; and in this the cater pillars yield to no kind, not to mention their silk, the spinning of which is one great proof of it. The sheaths and cases which some of these insects build for passing their transformations in, are by some made with their own hair, mixed with pieces of bark, leaves, and other parts of trees, with paper, and other ma terials ; and the structure of these is well worthy our attention. Yet there are others, whose workmanship in this article far exceeds these. There is one which builds in wood, and is able to give its case a hardness greater than that of the wood itself in its natural state. This is
the strange horned caterpillar of the wil low, which is one of those that eat their exuvive. This creature has extremely sharp teeth, and with these it cuts the wood into a number of small fragments ; these fragments it. afterwards unites to gether into a case, of what shape it pleases, by means of a peculiar silk, which is no other than a tough and viscous juice, which hardens as it dries, and is a strong and firm cement. The solidity of the case being thus provided for, we are to consider, that the caterpillar inclosed in it is to become a butterfly ; and the wonder is, in what manner a creature of this helpless kind, which has neither to dig, nor teeth to gnaw with, is to make its way out of so firm and strong a lodg ment as this in which it is hatched. The butterfly, as soon as hatched, discharges a liquor which softens the viscous matter that holds the case together ; and so its several fragments falling to pieces, the way lies open. iteaumur judged, from. the effects, that this liquor must be of a singular nature, and very different from the generality of animal fluids ; and in dissecting this creature in the caterpillar state, there will always he found near the mouth, and under the wsophagus, a blad der of the size of a small pea, hill of a limpid liquor, of a very quick and pene trating smell, and which, upon trial, proves to be a very powerful acid; and among other properties, which it has in common with other acids, it sensibly softens the glue of the case, on a common application. It is evident that this liquor, besides its use to the caterpillar; remains with it in the chrysalis state, and is what gives it a power of dissolving the struc ture of the case, and making its way through in a proper manner at the neces sary time.
Buerhaave adopted the opinion that there are no true acids in animals, except in the stomach or intestines ; but this familiar instance proves the contrary. Another very curious and mysterious arti fice is that by which some species of caterpillars, when the time of their chang ing into the chrysalis state is coming on, make themselves lodgments in the leaves of the trees, by rolling them up in such a manner as to make themselves a sort of hollow cylindric case, proportioned to the thickness of their body, well defended against the injuries of the air, and care fully secured for their state of tran quillity. Besides these caterpillars, which in this manner roll up the leaves of plants, there are other species which only bend them once, and others, which, by means of thin threads, connect many leaves to gether to make them a case. All this is a very surprising work, but much inferior to this method of rolling.
The different species of caterpillars have different inclinations, tint only in their spinning and their choice of food, but even in their manners and behaviour one to another. Some never part com pany from the time of their being hatched to their last change, but live and feed I together, and undergo together their change into the chrysalis state. Others separate one from another as soon as able to crawl about, and each seeks its for tune single ; and there are others which regularly live to a certain time of their lives in community, and then separate, each to shift for itself, and never to meet again in that state. See ENTOMOLOGY, INSECTS, &C.