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so free, hardly a moment, at other times, at rest, is, for many hours of many days together, fixed to her nest, as close as if her limbs were tied down by pins and wires. For my part, I never see a bird in that situation, but I recognise an invisible hand, detaining the contented prisoner from her fields and groves, for a purpose, as the event proved, the most worthy of the facrifice, the most important, the most beneficial.
But the loss of liberty is not the whole of what the procreant bird suffers. Harvey tells us, that he has often found the female wasted to skin and bone by sitting upon her eggs. .
One observation more, and I will dismiss the subject. The pairing of birds, and the non-pair* ing of beasts, forms a distinction, between the two classes, which shews, that the conjugal instinct; 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 sustentation. In the feathered race, the young bird is supplied by an importation
of of food, to procure and bring home which, in a sufficient quantity for the demand of a numerous brood, requires the industry of both parents. In this difference we see a reason, for the vagrant instinct of the quadruped, and for the faithful love of the feathered mate.
W.E are not writing a system of natural history; therefore, we have not attended to the class s, into which the subjects of that science we distributed. What we had to observe concerning different species of animals, sell easily, for the most part, within the divisions, which the course of our argument led us to adopt. There remain, however, some remarks upon the inseEl tribe, which could not properly be introduced under any of these heads; and which therefore we have collected into a chapter by themselves.
The structure, and the use of the parts, of insects are less understood than that of quadrupeds and birds, not only by reason of their minuteness, dr the minuteness of their parts, (for that minuteness we can, in some measure, follow with ghsses) but also, by reason of the remoteness of their manners and modes of life fiQm those of larger animals. For instance;
Insects, Insects, under all their varieties of form, are endowed with antenna, which is the name given to those 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 subservient, 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 possess 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 insects. We want a ground of analogy. This difficulty stands in our way as to some particulars in the insect constitution which we might wish to be acquainted with. Nevertheless, there are many contrivances in the bodies of insects, neither dubious in their use, nor obscure in their structure, and most properly mechanical. These form parts of our argument.
I. The elytra, or scaly wings of the genus of scarabæus or beetle, furnish an instance of this kind. The true wing of the animal is a light transparent membrane, finer than the finest 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 structure, and, perhaps, also to preserve it in a due state of suppleness and humidity, a" strong, hard, case is given to it, in the shape of the horny wing which we call the elytron. When the animal is at rest, 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 tissue of cordage, i. e. of muscular tendons, must run, in various and complicated, but determinate directions, along this fine surface, in order to enable the animal, either to gather it up into a certain precise form, whenever it desires to place its wings under the shelter which nature hath given to them; or to expand again their folds, when wanted for action.