84 THE LIFE-STORY OF INSECTS [CH. 



nymphalid butterfly attaches its cremaster to the 

 silken pad which the larva has spun in preparation 

 for pupation, is worthy of brief attention. The 

 caterpillar, hanging head downwards, is attached to 

 the silken pad by its hindmost pair of pro-legs or 

 claspers and by the suranal plate, and the cuticle is 

 slowly worked off from before backwards, so as to 

 expose the pupa. Were the process of moulting to 

 be simply completed while the insect hangs by the 

 claspers, the pupa would of course fall to the ground. 

 But there is enough adhesion between the pupal 

 and larval cuticles at the hinder end of the body, 

 especially by means of the everted lining of the hind- 

 gut, for the pupa to be supported while it jerks its 

 cremaster out of the larval cuticle and works it into 

 the meshes of the silken pad. The moult is thus 

 completed and the pupa hangs securely all the time. 

 In the numerous cases where the pupa is enclosed 

 in a cocoon, the cremaster serves to fix the pupa to 

 the surrounding silk. Chapman (1893) has drawn 

 attention to the fact that among the more highly 

 organised moths the pupa remains in the cocoon, 

 the emergence being entirely left to the imago, while 

 the pupae of the more primitive moths work their 

 way partly out of the cocoon before the final moult 

 begins. In the latter case, the cremaster is anchored 

 by a strand of silk which allows a certain degree of 

 emergence, and the pupa has rows of spines on its 



