10 



BULLETIN 435, U. S. DEPARTMENT OF AGRICULTURE. 



LARVAL FEEDING PERIOD. 



As fast as the larvae hatched in the laboratory they were trans- 

 ferred to the leaves of young trees growing within cages of wire net- 

 ting. When placed upon the leaf the newly hatched larva imme- 

 diately crawled to the underside of the leaf and began the construc- 

 tion of its silken web, as previously described. About this time (June 

 24) young larvae were very abundant in the young unsprayed orchards 

 in the vicinity of Winchester, Va. During the remainder of the 

 summer the larvae continued to feed upon the leaves, the length of the 

 feeding period therefore being directly dependent on the time the 

 individual infested apple leaves begin to drop in the fall. The leaves 

 infested by the apple leaf-sewer usually fall before the rest of the 

 normal foliage, owing to then weakened condition. In 1914 the 

 leaves continued upon the trees until about November 20, while in 

 1915 they had all fallen to the ground by November 6. Table V shows 

 the feeding period of the larvae. 



Table X —Feeding period of the larvas of the apple leaf-sewer, Winchester, Va., 1915. 





Date- 





Number 

 of indi- 





Number 







viduals. 



Began 



Leaf 



feeding. 





feeding. 



dropped. 





1 



June 15 



Nor. 3 



141 



1 



June 16 



Nov. 1 



138 



1 



June 17 



Oct. 30 



135 



1 



June IS 



Oct. 31 



135 



1 



June 19 



Nov. 6 



140 



1 



June 20 



Ocr. 31 



133 



1 



June 22 



N ov. 5 



136 



2 



June 2-3 ...do 



135 



2 



June 25 



Nov. 1 



129 



1 



June 26 



Nov. 2 



129 



1 



June 30 



...do.... 



125 



2 



July 2 



Nov. 4 



125 



Total. 15 







At 





132. 66 

 141 



123 



Max. . . 





Min 











The shortest feeding period was 125 days, the longest 141, while 

 the average for 15 observations was 132.66 clays. The leaves become 

 dry and hard within 2 or 3 days after falling. The feeding period of 

 the individual larva was therefore considered as completed when the 

 leaf infested by it had fallen from the tree. 



HIBERNATION. 



When the folded leaf containing the larva falls to the ground in the 

 late fall, the larva hues the inside of the folds with silk and hibernates 

 until spring. Experiments indicate that the larvae hibernating in the 

 fallen leaves are able to withstand great extremes of moisture and 

 temperature conditions, and that a larger proportion of them suc- 

 cessfully withstand the winter than would ordinarily be supposed. 



