10 BULLETIN 598, U. S. DEPARTMENT OF AGRICULTURE. 



Eighth feeding stage (including only larvae that spun cocoons at end of this 

 Instar) : Minimum 19 days, maximum 29 days, average 23.29 days; 7 larvae 



Jn*& feeding stage (until spinning of cocoons) : Minimum 13 days, maxi- 

 mum 26 days, average 20.95 days; 138 larva reared. 



The period covered by the rearing records in 1915 began when the 

 larvse under observation hatched, on July 17, and continued until 

 time of spinning cocoons, which extended from September 17 to 

 October 10. In 1916 the earliest larvae hatched June 30, and the 

 first cocoon under observation was spun September 24 and the latest 

 October 10. 



DURATION OF PREPUPA PERIOD. 



The larva period in the cocoon at North East, Pa,, in 1916 aver- 

 aged between 7 and 8 days. Of 19 larvae which spun cocoons on 

 September 24, 25, and 26, 10 pupated in 7 days and 9 in 8 days. 



HABITS. 



THE LARVA. 



Larvse from the same egg mass hatch almost simultaneously and 

 upon hatching eat the greater part of the eggshells. They are gre- 

 garious in the early stages, and even in the later stages molt together. 

 During the first four stages they feed gregariously, beginning to scat- 

 ter in the latter part of the fourth. If during the first three stages 

 a larva is separated from its fellows and is placed on a separate leaf 

 or shoot, it will invariably find its way back to the others within a 

 few hours. When one leaf or shoot is stripped the larvae move in 

 mass to another, often to another part of the tree. 



After the fifth stage the larvae scatter more or less and are solitary 

 except about molting time. Often they migrate to trees quite a dis- 

 tance from the one on which the colony started. After the last molt 

 the larva? scatter widely. 



The molting of the majority of larvae from a given egg mass is 

 almost simultaneous, and at this time the gregarious habit is most 

 pronounced. Even after larvae have ^scattered over a tree they come 

 together to molt. A short time before molting a silken mat is spun 

 upon which the larvae rest for about a day before the early molts 

 and sometimes for several days before later ones. This molting mat 

 is spun upon a leaf or bunch of leaves, and sometimes before the later 

 molts on the side of a branch or tree trunk. At each molting period 

 there are often a few larvae which fall behind and fail to molt with 

 the rest. These invariably develop very slowly and usually do not 

 mature. 



