A SYNOPSIS OF THE APHIDIDAE 121 



The eggs are laid in the fall of the year, probably during the latter 

 part of October, throughout November, and on into December. They 

 are laid for the most part on the smooth bark of the suckers and water 

 sprouts of the newer shoots. The author has found them in the 

 crotches of the twigs and stems where the bark is rougher, but this is 

 not the usual place. These eggs hatch in the spring about the time 

 the buds begin to show green. In California this is usually during 

 March, although some seasons it is as early as the middle of February, 

 depending entirely upon the weather conditions. These stem-mothers 

 at first feed on the young buds, until the latter have opened enough 

 to allow the aphids to crawl down into the curled leaves. Here they 

 feed for two or three weeks, when they mature and begin depositing 

 living young. This second generation consists chiefly of apterous 

 females, which mature in from two to four weeks and in turn produce 

 young. The following generations are in large part alate females 

 which migrate to other trees and there form new colonies. The alates 

 are most common at Stanford University during the latter part of 

 May and during the month of June. After June they seem to lessen 

 in number, perhaps due to the predaceous and parasitic enemies. The 

 first alates that the author has found in the spring were taken at 

 Stanford University on April 13, 1914. In the fall, often as early as 

 October, sexual males and females begin to appear, the males being 

 apterous, the females alate. These mate and very soon the female 

 lays its eggs. Egg laying begins usually in the latter part of October, 

 just as the leaves are beginning to fall, and continues into December 

 after the trees are bare. These eggs hatch in the spring into stem 

 mothers, and the life cycle is completed. 



140. Aphis prunorum Dobr. 



Figures 228 to 230 



Dobrowljansky, Zur Biol. d. Blattlause d. Abstbaume u. Biirenstaucher, 1913 



(orig. desc.). 

 Patch, Maine Agr. Exp. Sta., Bull. 233, p. 262, 1914 (desc. note). 



Records. Prunus domestica; Walnut Creek (Davidson) ; San Francisco, April, 

 1915 (Shinji). 



A species of Aphis, supposed to be this species, has been taken on 

 prune and plum in the San Francisco Bay region. It agrees very well 

 with Dr. Patch's description listed. However, it may prove to be 

 synonymous with Siphocoryne nymphaeae (Linn.). 



