44 BULLETIN" 173, IT. S. DEPARTMENT OF AGRICULTURE. 



numbers in the interior valleys of Contra Costa, Sacramento, and 

 Solano Counties the last of March and the first 10 days of April, while 

 the maximum number in Santa Clara County appear the first 15 days 

 of April and the last ones in all the infested regions are found some 

 time in early May. 



TIME SPENT IN FEEDING. 



The time spent in feeding, or the period required for the larvae to 

 obtain their growth, is from two to three weeks, for individuals. For 

 the whole brood — that is, from the time the first larvae are found on 

 any variety of fruit to the time the last ones are found in the trees — 

 a period of about two months and a half is spent, from the latter part 

 of February to the early part of May. 



MOLTS. 



After the larvae have hatched and fed for some seven or eight days 

 they shed then skins, becoming more robust, and ovoid in shape, and 

 in this form they continue until they molt again into the prepupal 

 stage while in the ground. After the larvae have molted the first 

 time they remain upon the tree from ten clays to two weeks before 

 becoming full grown and dropping to the ground. The total time 

 spent upon the tree is from two to three weeks. 



LEAVING TREES AND ENTERING GROUND. 



On leaving the trees the larvae do not crawl down but either fall or 

 are knocked off by rains or shaken off by winds. A large number 

 fall with the dropping calyces. Numerous instances were recorded 

 in the year 1910 in which heavy rains knocked off large numbers of 

 larvae, some of which reached their full growth by feeding upon 

 miner's lettuce, which was at the time the only vegetation growing in 

 this orchard; but many of these immature larvae were quite small and 

 failed to reach full growth, which is partly responsible for the smaller 

 number of adults in some sections the following year, 1911. The 

 young and only partially grown larvae that fall off the trees and do 

 not come in contact with any weed or grass in the orchard mostly 

 perish. Only the full-grown larvae that fall to the ground in culti- 

 vated orchards work their way into soil Larvae that fall off normally 

 do not ascend the trees again, but in some cases in cherry orchards 

 where foliage was near the ground on the trunks of the trees many of 

 the larvae were noted to crawl back to lower foliage. This would not 

 be likely to occur on pears or prunes, where there is little or no 

 foliage near the ground. 



