GENERAL REMARKS. Ill 



pp. i6o, 199). The pupal stage is passed, as a rule, 

 in more or less sheltered situations, and it is either 

 enclosed in a special covering, a cocoon, woven by 

 the animal, or else protected by one acquired through 

 the moulting and hardening of its own cuticle. " The 

 difference between this last and the ordinary process 

 of moulting consists in the retention of the moulted 

 skin, the animal shrinking within it for shelter as its 

 fatty parts are consumed, instead of casting it off alto- 

 gether. 



Lubbock, in his Origi7i mid Metamorphoses of In- 

 sects} has shown that the inactivity of the pupa in the 

 second series of orders is not a novel condition, but 

 a mere prolongation of the shorter periods of inactivity 

 which necessarily accompany eyery change of skin or 

 moult. These facts and the obvious want of any 

 common structural differences in the quiescent pupae, 

 as compared with the similar stages of active pupae, 

 show that quiescence must be reckoned as a habit of 

 resting from active exertion during a more or less 

 prolonged period of their growth which has been 

 acquired by the more speciaHzed forms of insects, 

 not only generally among the members of the second 

 series of orders, but also by many among the first 

 series. The degraded larvae of individuals in these 

 specialized forms are as a rule farther removed struc- 

 turally from their own adults, than in forms having 

 a direct mode of development, and the changes to 

 be gone through before reaching the adult stage are 

 greater and more numerous. The habits of the ani- 



1 See pp. 67-70. 



