20 CATERPILLARS AND THEIR MOTHS 



top of its head, like little wedges, to open a way 

 through the earth. 



The pupsB of larvae which spin cocoons have one 

 means of helping the moth to emerge. Most, if not 

 all, of them have one or more little hooks on the tip 

 of the abdomen, which catch in the silk of the cocoon 

 and hold the pupa-skin firmly in place so that the 

 moth can crawl out without carrying the pupa-skin 

 too. 



The triangular tip of the abdomen of the pupa is 

 called the cremaster, and corresponds to the anal, also 

 called the siir-anal, plate of the caterpillar. 



The moths themselves have various means of for- 

 cing an opening in the cocoons. Some have rough 

 spines or knobs on their heads with which they cut 

 the silken threads until they can push through them. 

 Some have on their shoulders strong spines with five 

 or six teeth, like saws, and cut their way through the 

 cocoon with these. Others moisten the silk with a 

 fluid secreted in the mouth, and acid enough to soften 

 or dissolve the silk. We have often known that a 

 moth was about to emerge by finding the end of the 

 cocoon wet, and several times we have saved the life 

 of the moth by opening the cocoon and taking the 

 moth out when the fluid failed to serve its purpose, as 

 sometimes happens. Either there is not enough of it 

 or it lacks acid, and in this case the poor moth dies in 

 its cocoon unless some one rescues it. We have found 

 cocoons each containing a much-broken j)upa-skin, a 

 dead moth, and from sixty to two hundred eggs, these 

 being laid all over the pupa-skin and the inside of the 

 cocoon, showing that the moth had turned inside it 



