182 OF INSECTS. 



formed for liberty, sul)mits to confinement, in tlie very sea- 

 son when every thing invites her abroad : what is more, an 

 animal delighting in motion, made for motion, ail whose 

 motions are so easy and so free, hardly a moment, at other 

 times, at rest, is, for inany hours of many days together, 

 fixed to her nest, as close as if her limbs were tied down by 

 pins and wires. For my j)art, 1 never see a bird in that 

 situation, but I recognize an invisible haiid, detaining the 

 contented prisoner from her fields and groves, for a i)urpose, 

 as the event j)roves, the most worthy of the sacrifice, the 

 most imi)ortant, the most beneficial. 



But the loss of liberty is not the whole of wliat the pro- 

 creant 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 nun-pairing of beasts, forms 

 a distinctioii between the two classes, which shows that the 

 conjugal instinct is modified with a reference to utility, 

 founded on the condition of the ofispring. 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 susteatation. Tn tlie feathered race, the 

 young bird is supplied by an importation of food, to procure 

 and bring home, which, in a sufficient quantity for the de- 

 mand 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 tho 

 feathered mate. 



CHAP. XIX. 



OP INSECTS. 



We are not writing a system of natural history ; there- 

 fore, we have not attended to the classes, into wliich the 

 subjects of that science are distributed. What we had to 

 observe concerning different species of animals, fell 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 insect tribe, which could not prop- 

 erly 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 (juadrupeds and birds, not only 



