CHAPTER XIX. OF INSECTS. WE are not writing a system of natural his tory; therefore, we have not attended to the claffes, into which the fubjects of that science are diftributed. What we had to obferve concerning different fpecies of animals, fell eafily, for the most part, within the divifions, which the course of our argument led us to adopt. There remain, however, fome remarks upon the infect tribe, which could not properly be introduced under any of these heads; and which therefore we have collected into a chapter by themselves. The ftructure, and the use of the parts, of infects, are lefs understood than that of quadrupeds and birds, not only by reason of their minuteness, or the minuteness of their parts, (for that minuteness we can, in some measure, follow with glaffes) but also, by reason of the remoteness of their manners and modes of life from those of larger animals. For instance; Infects, Infects, under all their varieties of form, are endowed with antenna, which is the name given to thofe long feelers that rise from each fide of the head; but to what common use or want of the insect kind, a provision so univerfal is fubfervient, has not yet been ascertained; and it has not been ascertained, because it admits not of a clear, or very probable, comparison, with any organs which we poffefs ourselves, or with the organs of animals which resemble ourselves in their functions and faculties, or with which we are better acquainted than we are with infects. We want a ground of analogy. This difficulty stands in our way as to fome particulars in the infect conftitution which we might wish to be acquainted with. Nevertheless, there are many contrivances in the bodies of infects, neither dubious in their use, nor obfcure in their structure, and moft properly mechanical. These form parts of our argument. I. The elytra, or fcaly wings of the genus of scarabæus or beetle, furnish an inftance of this kind. The true wing of the animal is a light transparent membrane, finer than the fineft gauze, and not unlike it. It is alfo when expanded, in proportion to the size of the the animal, very large. In order to protect this delicate ftructure, and, perhaps, also to preferve it in a due ftate of fuppleness and humidity, a ftrong, hard, cafe is given to it, in the shape of the horny wing which we call the elytron. When the animal is at reft, the gauze wings lie folded up under this impenetrable shield. When the beetle prepares for flying, he raises the integument, and spreads out his thin membrane to the air. And it cannot be observed without admiration, what a tiffue of cordage, i. e. of mufcular tendons, muft run, in various and complicated, but determinate directions, along this fine furface, in order to enable the animal, either to gather it up into a certain precife form, whenever it defires to place its wings under the shelter which nature hath given to them; or to expand again their folds, when wanted for action. In fome infects, the elytra cover the whole body; in others, half; in others, only a finall part of it; but in all they completely hide and cover the true wings. Also, Many or most of the beetle fpecies lodge in holes in the earth, environed by hard, rough, fubftances, and have frequently to squeeze their way through narrow paffages; in which fituation, wings so tender, and so large, could fcarcely have escaped injury, without both a firm covering to defend them, and the capacity of collecting themselves up under its protection. II. Another contrivance, equally mechanical, and equally clear, is the awl or borer fixed at the tails of various fpecies of flies; and with which they pierce, in fome cafes, plants; in others, wood; in others, the skin and flesh of animals; in others, the coat of the chryfalis of infects of a different species from their own; and in others, even lime, mortar, and ftone. I need not add, that having pierced the substance, they depofit their eggs in the hole. The descriptions, which naturalifts give of this organ, are fuch as the following. It is a fharp-pointed inftrument, which, in its inactive state, lies concealed in the extremity of the abdomen, and which the animal draws out at pleasure, for the purpose of making a puncture in the leaves, ftem, or bark of the particular plant, which is fuited to the nourishment of its young. In a fheath, which divides and opens whenever the organ is used, there is inclofed, a compact, folid, dentated ftem, along along which runs a gutter or groove, by which groove, after the penetration is effected, the egg, affisted, in fome cafes, by a peristaltic motion, paffes to its deftined lodgment. In the œftrum or gadfly, the wimble draws out like the pieces of a spy-glass; the last piece is armed with three hooks, and is able to bore through the hide of an ox. Can any thing more be necessary to display the mechanism, than to relate the fact? III. The ftings of infects, though for a different purpose, are, in their structure, not unlike the piercer. The sharpness to which the point in all of them is wrought; the temper and firmness of the fubftance of which it is compofed; the ftrength of the muscles by which it is darted out, compared with the finallness and weakness of the infect, and with the foft or friable texture of the reft of the body; are properties of the fling to be noticed, and not a little to be admired. The fting of a bee will pierce through a goatskin glove. It penetrates the human skin more readily than the finest point of a needle. The action of the fting affords an example of the union of chymistry and mechanism, fuch as, if it be not a proof of contrivance, nothing is. First, as to the |