Pagina-afbeeldingen
PDF
ePub

fo free, hardly a moment, at other times, at reft, is, for many hours of many days together, fixed to her neft, as close as if her limbs were tied down by pins and wires. For my part, I never fee a bird in that fituation, but I recognise an invifible hand, detaining the contented prifoner from her fields and groves, for a purpose, as the event proves, the most worthy of the facrifice, the most important, the most beneficial.

But the lofs of liberty is not the whole of what the procreant bird fuffers. Harvey tells us, that he has often found the female wafted to skin and bone by fitting upon her eggs.

One observation more, and I will dismiss the fubject. The pairing of birds, and the non-pairing of beasts, forms a diftinction, between the two claffes, which fhews, that the conjugal inftinct is modified with a reference to utility founded in the condition of the offspring. In quadrupeds, the young animal draws its nutriment from the body of the dam. The male parent neither does, nor can, contribute any part to its fuftentation. In the feathered race, the young bird is fupplied by an importation

of

of food, to procure and bring home which, in a fufficient quantity for the demand of a numerous brood, requires the industry of both parents. In this difference we fee a reason, for the vagrant inftinct of the quadruped, and for the faithful love of the feathered mate,

CHAP

CHAPTER XIX.

OF INSECTS.

We are not writing a system of natural hisWE

E

tory; therefore, we have not attended to the claffes, into which the subjects of that science are diftributed. What we had to observe 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 minutenefs of their parts, (for that minutenefs we can, in some measure, follow with glaffes) but also, by reason of the remoteness of their manners and modes of life from thofe 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 infect kind, a provifion fo 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 refemble 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 ftands 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 ftructure, and most properly mechanical. Thefe form parts of our argument.

I. The elytra, or fcaly wings of the genus of fcarabæus 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 alto 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` strong, hard, cafe is given to it, in the shape of the horny wing which we cal! the elytron. When the animal is at reft, the gauze wings lie folded up under this impenetrable fhield. When the beetle prepares for flying, he raises the integument, and spreads

out his thin membrane to the air. And it cannot be obferved without admiration, what a tiffue of cordage, i. e. of mufcular tendons, must 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 ac

tion.

In fome infects, the elytra cover the whole body; in others, half; in others, only a small part of it; but in all they completely hide and cover the true wings. Also,

Many or most of the beetle species lodge in holes in the earth, environed by hard, rough, fubftances, and have frequently to squeeze

« VorigeDoorgaan »