ePub 版

mediately from the abdomen, and is thickest at its 6tigin, although there are some insects which have it thicker below than above. The second is the kg, properly so called, (tibia.) The articulations of these parts in some insects are furniflied with strong and sharp spines. Ihe third part is (he foot, s tarsus,J *hich deserves more attention than the other two.

It is generally articulated, the parts sometimes round or heart shaped. Some have two articulations^ some more, the length of five. At the extremity of these, some have two hooked appendices, by which they attach themselves to the most polished substances.—*' Between these, others have something like the sole of a foot, which enables them to' stick to places where she hooks would be useless. It produces the fame effect as the bit of moistened leather which children prefe upon a stone ; it adheres so strongly, thata very heavy stone may be lifted by it. Some have a sort of cup at the knee joint, by which they aflix themselves strongly to the bodies they want to hold.by*

The legs of insects likewise serve various purposes, ind chiefly for walking. But there are some, which use them merely as hooks for fastening themselves to objects, others for leaping. The leaps they make are so great, that it is said a flea will leap 200 times its own length. For this purpose, these insects are furnished, not only with strong and flexible legs and thighs, but with vigorous muscles, endowed with a power of elasticity, which raises the animal high ia the air. The feet serve as a rudder to those insects? which swim, directing them to the place they want .to reach* They hold in equilibrium, the body of those that fly, and direct it at the pleasure of the animaL They receive the same advantages from them that storks do from their long legs. They stretch them out from the abdemen, and use them: aa

". . a' a rudder to steer them. Others, which are shortsighted, use them for exploring the road, both before and.behind them. Some .employ them in cleaning f»eir ,eyes, their antenna, and their, wings, and in clearing them of the dust and earth which might incommode them. Those which dig in the earth, use their legs as pick-axes, to make cavities and subterraneous passages. As men use their arms, and some animals their feetj as weapons of defence, there are insects which make the fame use of theirs. I believe I have already mentioned that some use them for seizing and holding their prey. Lastly, by the struc. ture of the legs, the species of infects are often distinguishable. / ..

.' The wings are the principal things to be noticed in winged insects. I have already spoken above of the number which the different kinds of insects possess; and have observed, that some have two, others four. They are so delicate, and their structure discovers so much art, that they may well pass for one of those objects that most clearly demonstrate the wisdom of the Creator. They are provided with different nerves, which, like those of leaves, are distributed in different directions. The position of them is also different, in different insects. , In some they are horizontal, in others they decline a little towards the sides, and in others, they stand erect. The remarks which I have had occasion to make in some of the preceding articles, sufficiently shew, that the wings of insects are very various. Some have a kind of a covering over them, while others are bare. Some of these last are exceedingly thin, shining, and transparrent, like parchment or fine gauze; others are opaque, and covered with a sort of farina or powder.' I have also already examined the different sorts of butterflies and winged beetles, so that I have only here to treat of the wings themselves. ♦■' , The

The wings of insects, which are bare, whether they have two or four, are exceedingly thin, and their nerves are ramified in different directions. In some, these ramifications extend from the body to the half of the wings only, where they are loft and disappear, as in the Hippobosca equina. In others they reach the margin'of the wings, where they join and form a spot, which Frisch calls the marginal spot, as in the Hemerobius Chrysops. These ramifications assume various figures. Sometimes they are squares, which, at the superior extremity divide into three branches, as in some Libellulas, in others they are rhomboidical, as in the grasshoppers, pentagonal, or irregularly pentagonal, as in the Sphex sabuiosa: the membrane that fills up the interstices of these nerves is so thin, that it can hardly be perceived, and the whole wing appears like thin gauze.

There is great diversity in the figure of the farinaceous wings. They mny be compared -to the leaves of different trees; whatever connection there may be among them, there is not one of them like another. They are round, long, heart-shaped, indented, <or intire in the margins, oval, or nearly oval, their ends terminating in a point; in others they form triangles, the ends being either pointed or rounded. The margin of the wings is often indented like the edge of a saw, or undulated, forming semicircles like the figure of a serpent in motion; and sometimes between these circles there are small elevations. Some at the extremity of the wings have a fort of tail, like that of a swallow, some have it ornamented with fine fringes like lace.

When the dust which covers the wings of insects is looked at with the naked eye, one would .take it for nothing but fine farina or powder; but, if it is seen through a magnifier, this pretended dust appears

X ia in the form of very delicate feathers, which easily come off on being touched. The small feathers are of very different figures; some have the form of a a battledore with a short handle, others are almost oval, except at the base, where they are a little notched; some are like-the leaves of a willow, except that they are sometimes indented at top: some resemble £ fan, a square with rounded angles, but waved at top5 others are pointed at the base, and enlarge gradually, terminating in two, three, four, and even five long points like a finger; some resemble the heart-shaped leaves of trees, and terminate in two or three hooked points; others are oblong, and pointed at their origin, where they are oval, and have at the extremity, three, four, and even a greater number of short points; lastly, some are long, thickening at the base, slender in the middle, and are twice as broad at the top, as at the bottom*

Without taking into account, the different colours of these wings, of which we shall hereafter take notice, many are marked with singular characters. On the wings of some, are marks which resemble Hebrew lettefs, on others a Roman C, a Greek Upsilon* a V, or an O. Madame Merian observed ,^ on the wings of a butterfly, characters resembling the letters BC YM; this I have not myself seen. Others are marked with a St Andrew's cross, and some with the figure of an arrow.

The wirtgs that have cafes are ftot less worthy of attention than the others 5 these cases aTe hard as horn, and are easily broken. They are like a sheath to the delicate wings, which they cover and preserve from injury. As infects have no bones, these serve Instead of them externally. They are not of equal hardness in ail insects, the genus of Cantharis has them thin and flexible, and Frifch fays of the Ganthaws fufca, <hat when it dies, the elytra shrivel up. There is likewise great diversity in their length; in some, they cover only a small part of the body below the thorax, in others they cover the half of it; in some they hardly reach the extremity of the abdomen, in others they cover the whole of it. Sometimes these cases are nearly opaque, and hard as horn; in others thin and nearly transparent. Not less variety is observable in their shape. Some, when jpined together, are round, like the section of a sphere, others oval, oblong, or straight. Some are exceedingly smooth and polished, others have a border, or are dotted with little depressions, as if made with a pin. Some have longitudinal lines like the furrows of a ploughed field, and others are set with hairs, or adorned with little tubercles, covering the surface.'

The wings to which these cases serve as covers are very fine and transparent. In some species they are not longer than the cafes themselves and may be covered therefore without being folded. But there are others which have them much longer, and must: fold them up when they are not flying to put them under the eiytra. For this purpose they have at the external margin an articulation or a kind of spring to fold up what is longer than the cafes. When these wings are laid on the hack, their largest nerves are without support, and the two ends which are too long hang down. But when the elytra are laid, down to cover them, they lower at the fame time these nerves, and then the two ends drawn by their muscles are folded in, and take their proper place. Li order to accomplish this, the beetle has nothing to do but to leave a small space between the elytra and abdomen that what remains of the wing may the Biore easily be folded: and this happens with all

X i Jhpsc

« 上一頁繼續 »