76 NATURAL HISTORY. [CH. III. 



of this mode of proceeding ; the empty chrysalis 

 cases of which may constantly be found sticking 



half out of holes in rotten willow trees. This is 

 effected by sharp points upon the head of the pupa, 

 which are employed for the purpose of making the 

 first breach in the cocoon, through which the body 

 is subsequently further protruded by the assistance 

 of a series of sharp hooks along its rings, by which 

 it is enabled to keep itself in its advanced position 

 when it makes a small further advance, and thus 

 repeats the operation until a considerable portion is 

 protruded into the open air. 



In the fifteenth chapter of our former volume we 

 have given the history of several caterpillars that 

 construct cases in which they reside, and which 

 they carry about with them. When these cater- 

 pillars have attained their full size, they fix the 

 lower end of their cases, from which the head was 

 previously protruded, to the adjacent objects, so 

 that these cases also serve them as cocoons. Of 

 these caterpillars, the species of the genus Psyche 

 exhibit some extraordinary circumstances. One of 

 these, which we have observed, is, that the male 

 moths make their escape from the opposite end of 

 the case, by first protruding the head of the chrysa- 

 lis out of that end of the case which was originally 



