INSECT A. 167 



before entering the pupa stage — spins for itself a protective case of 

 sillcen threads, which surrounds the chrysalis, and is known as the 

 " cocoon." Having remained for a variable time in this inanimate, 

 quiescent pupa-stage, during which rapid changes have been going 

 on in the interior of the animal, the insect now frees itssK from the 

 envelope which obscured it, and appears as the perfect winged adult 

 or imago. 



