HABITS OF THE CATERPILLARS 83 



According to some observations made by my assistant, 

 Mr. W. F. Fiske, to whom I am indebted for a number of 

 observations upon this insect, the young caterpillars if sud- 

 denly disturbed while feeding will drop to the ground without 

 attaching their threads. A large proportion of the caterpillars 

 drop oft' by means of a thread at one time or another during 

 their growth : some are probably startled by the swaying of 

 the twig in the wind; others by birds when alighting; in 

 many cases the movement is probably induced by the exhaus- 

 tion of the food supply, or, perhaps, by a migratory instinct. 

 In any event, this dropping is very general, and as a result the 

 caterpillars are continually to be seen crawling up the trunks 

 of the trees ; this is especially likely to be the case early in the 

 morning. 



The larvae generally crawl along the limbs in single file. 

 As they go, each spins from its mouth a delicate silken thread. 



FIG. 27. Apple leaves partially eaten by Forest Tent Caterpillars. 



When not eating, they congregate in masses upon the larger 

 limbs, with an indistinct web beneath them, although generally 

 there is no web over them, as is the case with the American 

 Tent Caterpillar. 



In feeding, especially as they approach maturity, the cater- 



