MODES OF EMERGING FROM PUP-K. 323 



thin as writing-paper. The head of this pupa being 

 obtuse , it cannot of course cut through this wooden 

 covering, thin as it is, hut can only push against it till 

 it burst it open, which we have more than once seen it 

 actually do.* It is enabled to exert considerable force 

 in this process, by means of the beautifully serrated 

 structure of its rings, resembling in this respect the 

 caterpillars of cossus and other wood-borers. 



pupse of Cossus, a, and -<2Jg-m, 6, showing the serratures of their 

 rings. 



Lyonnet justly remarks that in the cossus there are 

 sharp points upon the head for the purpose of making 

 the first breach, the rest of the body acting as a wedge 

 to tear open the cocoon. Professor Peck has given a 

 very interesting account of similar proceedings in the 

 case of the locust moth ( Cossus Robinice, PECK). * In 

 the silk moth,' he says, * and all others which I have 

 had an opportunity to observe, the chrysalis bursts in 

 the cocoon, and the fluid which surrounded the new 

 insect in it escaping at the same time, so weakens or 

 dissolves the fibre and texture of the silk,! that the moth 

 is able to extricate itself, leaving the chrysalis behind it; 

 but this is not the manner in the locust moth. After re- 

 maining till all its parts are fully grown, and it is ready 

 to quit its prison, a certain quantity of exercise is ne- 

 cessary to. break the ligaments which attach the moth 



+ J. R. 



t See some observations on this doctrine, * Insect Architec- 

 ture,' pages 316, 317, and 195. 



