Pagina-afbeeldingen
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their way through narrow paffages; in which fituation, wings fo tender, and fo large, could fcarcely have escaped injury, without both a firm covering to defend them, and the capacity of collecting themselves up under its pro

tection.

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 fkin and flesh of animals; in others, the coat of the chryfalis of infects of a different fpecies from their own; and in others, even lime, mortar, and ftone. I need not add, that having pierced the fubftance, they depofit their eggs in the hole. The defcriptions, which naturalists 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 inclosed, a compact, folid, dentated stem,

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along which runs a gutter or groove, by which groove, after the penetration is effected, the egg, affifted, 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 fpy-glafs; the laft piece is armed with three hooks, and is able to bore through the hide of an ox. Can any thing more be neceffary to difplay the mechanism, than to relate the fact?

III. The flings 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 mufcles by which it is darted out, compared with the smallness 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 fineft point of a needle. The action of the fting affords an example of the union of chymistry and mechanism, such as, if it be not a proof of contrivance, nothing is.. First, as to

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the chymistry; how highly concentrated must be the venom, which, in so small a quantity, can produce fuch powerful effects? And in the bee we may observe, that this venom is made from honey, the only food of the infect, but the last material from which I fhould have expected, that an exalted poifon could, by any process or digestion whatsoever, have been prepared. In the next place, with respect to the mechanism, the fting is not a fimple, but a compound inftrument. The vifible fting, though drawn to a point exquifitely fharp, is in ftritnefs only a sheath; for, near to the extremity, may be perceived by the microscope two minute orifices, from which orifices, in the act of ftinging, and, as it fhould feem, after the point of the main fting has buried itself in the flesh, are lanched out two fubtile rays, which may be called the true or proper ftings, as being those, through which the poifon is infufed into the puncture already made by the exterior fting. I have faid that chymistry and mechanism are here united: by which obfervation I meant, that all this machinery would have been useless, telum imbelle, if a fupply of poison, intense in quality, in proportion to the fmallness of the drop, had not been fur

nished to it by the chymical elaboration which was carried on in the infect's body and that, on the other hand, the poison, the refult of this procefs, could not have attained its effect, or reached its enemy, if, when it was collected at the extremity of the abdomen, it had not found there a machinery, fitted to conduct it to the external fituations in which it was to operate, viz. an awl to bore a hole, and a fyringe to inject the fluid. Yet these attributes, though combined in their action, are independent in their origin. The venom does not breed the fting; nor does the fting concoct the venom.

IV. The probofcis, with which many infects are endowed, comes next in order to be confidered. It is a tube attached to the head of the animal. In the bee, it is compofed of two pieces, connected by a joint: for, if it were conftantly extended, it would be too much expofed to accidental injuries: therefore, in its indolent ftate, it is doubled up by means of the joint, and in that pofition lies fecure under a fcaly penthoufe. In many fpecies of the butterfly, the probofcis, when not in ufe, is coiled up like a watch-fpring. In the fame bee, the probofcis ferves the office of the mouth, the infect having no other:

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and how much better adapted it is, than a mouth would be, for the collecting of the proper nourishment of the animal, is fufficiently evident. The food of the bee is the nectar of flowers; a drop of fyrup, lodged deep in the bottom of the corollæ, in the receffes of the petals, or down the neck of a monopetalous glove. Into these cells the bee thrufts its long narrow pump, through the cavity of which it fucks up this precious fluid, inacceffsible to every other approach. The ringlets of which the probofcis of the bee is compofed, the muscles by which it is extended and contracted, form fo many microscopical wonders. The agility alfo, with with it is moved, can hardly fail to excite admiration. But it is enough for our purpose to obferve in general, the fuitableness of the ftructure to the ufe, of the means to the end, and especially the wifdom, by which nature has departed from its moft general analogy (for animals being furnished with mouths is fuch) when the purpofe could be better anfwered by the deviation.

In fome infects, the probofcis, or tongue, or trunk, is fhut up in a fharp-pointed fheath, which fheath, being of a much firmer texture than the probofcis itself, as well as sharpened

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