TRANSFORMATIONS OF INSECTS. 



239 



them, although they are already free and separate from the body. Beetles and Bees and Wasps 

 furnish excellent examples of this condition, in which, although the parts of the future insects are 

 rudely indicated, and often capable of 

 moving a little under irritation, the general 

 characteristic of the insect is a state of 

 absolute repose. 



In other instances (such as the Moths 

 and Butterflies) we find that the parts of 

 the mature insect exist in the same way, 

 in an imperfectly developed state, but that 

 they are closely applied to the body within 

 their proper sheaths, and that a continuous 

 case of a more or less horny texture 

 envelops the whole, and renders all the 

 parts incapable of motion, except that the 

 abdomen can generally bend more or less. 

 This outer case follows all the inequalities 

 of the surface produced by the limbs, 

 antennae, wings, &c., which can thus be 

 distinguished as easily as in the preceding 

 forms. An insect in this condition is 

 commonly denominated a chrysalis ; it is, 

 of necessity, incapable of moving about or 

 taking nourishment. 



As these insects generally pass a 

 considerable time in this helpless and 

 inactive condition, during which the parts 

 of the perfect insects are being brought 



to maturity within them, the larvae, before undergoing the change above described, usually select some 

 suitable shelter for the purpose. Many burrow into the ground, and pass the interval of repose in 

 a chamber which secures them from the attacks of enemies and the inclemency of the weather; 

 others seek concealment in sheltered corners, or in the crevices of the bark of trees ; others again 

 content themselves with such protection as they can get by adhering closely to the stems or branches, 

 or the under side of the leaves of the plants on which they feed ; and not a few, even of those 

 which take up their abode in sheltered situations, spin for themselves a silken cocoon, within which 

 they pass their period of inactivity. In a very large proportion of two-winged flies, the transforma- 

 tion to the second stage takes place within the skin of the larva, which then dries and forms 

 a protective covering for the insect during its period of repose. 



The general name pitpce is applied to insects in this inactive state, in allusion to the swathed 

 appearance presented by the Moths and Butterflies at this period of their existence, pupa being the 

 Latin term for an infant in swaddling cloths. But the same denomination has also been extended to 

 the corresponding stage in the development of those insects which are active throughout their whole 

 life ; and thus we get the two categories of active and inactive pupae, from each of which the insect 

 emerges in the perfect, or, as it is called, the imayo state. The whole series of changes, here referred 

 to, constitute the transformations or metamorphoses of insects ; and according as the insect is active 

 or inactive in the pupa state, the metamorphosis is said to be imperfect or perfect. It will be seen 

 hereafter that this distinction is of great systematic importance, and that, in tracing the possible 

 genealogy of the class of insects, it is one of the principal matters to be considered. Here, however, 

 we must confine ourselves to such a general exposition of the phenomena of metamorphosis as will 

 suffice to render the subsequent chapters intelligible. 



The internal anatomy of insects requires some notice, but it must be passed over very briefly. 

 The idea of a segment, or somite, as it is now frequently termed, implies that of a repetitive 

 succession of parts, that is to say, each somite is to be regarded with certain limitations, as of the same 

 227 



Fig. 8. LARVA (A), CHRYSALIS (B), AND IMAGO (c) OF TAriLIO 

 MACHAON. 



