STATES OF INSECTS, 195 



regard to the moult of any insects besides the Lepido- 

 jptera. 



A day or two previously to each change of its skin, 

 the larva ceases eating altogether; it becomes languid 

 and feeble, its beautiful colours fade, and it seeks for a 

 retreat in which it can undergo this important and some- 

 times dangerous and even fatal operation in security. 

 Here, either fixing itself by its legs to the surface on 

 which it rests, or, as is the case with many caterpillars, 

 by its prolegs, to a slight web spun for this purpose, it 

 turns and twists its body in various directions, and alter- 

 nately swells and contracts its different segments. The 

 object of these motions and contortions seems to be, to 

 separate the exterior skin, now become dry and rigid, 

 from the new one just below it. After continuing these 

 operations for some hours, resting at intervals without 

 motion, as if exhausted by their violence, the critical mo- 

 ment arrives : the skin splits in the back, in conse- 

 quence of the still more violent swelling of the second or 

 thifd segment : the opening thus made is speedily in- 

 creased by a succession of swellings and contractions of 

 the remaining segments : even the head itself often di- 

 vides into three triangular pieces, and the inclosed larva 

 by degrees withdraws itself wholly from its old skin. 

 All larvae, however, do not force their way through this 

 skin in precisely the same place. Thus, those of the haw- 

 thorn butterfly (Pieris Crat<zgi\ according to Bonnet a , 

 make their way out by forcing off what may be called their 

 skull, or the horny part of their head, without splitting the 

 skin, which remains entire; others have been observed 

 to make their way out at the side and the belly. Reau- 



a CEuvr. ii. 71. 

 O 2 



