INTRODUCTION. XXXV 



three animals, in all respects specifically different, 

 whose manner of existing, and alimentary nourish- 

 ment, are diametrically opposite. 



Several of the vertebrate animals, such as frogs, 

 toads, and water newts, undergo metamorphoses in 

 some respects analogous to those of the insect tribes ; 

 the first form of these being a tadpole, which is 

 widely different from that which they afterwards 

 assume. These reptiles, too, as well as snakes, cast 

 their skins by an operation somewhat similar to the 

 larvae of insects. There is nothing, however, in 

 their metamorphosis at all resembling the pupa, or 

 chrysalis state in insects. * 



All insects pass through four states, namely, that 

 of the egg; the larva, or caterpillar; the pupa, or 

 chrysalis ; and the imago, or perfect insect. These 

 different forms I shall treat in succession. The egg 

 state will apply to the whole order ; but I shall only 

 enter into a general account of the physiology of 

 the larvae condition, as applied to the three genera, 

 Butterflies, Sphinges, and Moths, and give a detailed 

 account, in the first instance, of Butterflies ; reserving 

 the most singular facts which are connected with the 

 history of Moths, to precede the description of the 

 animals of that genus. 



* See KIRBY and SPENCE, Intr. v. pi. i. p. 81. 



