14 



FABMERS BULLETIN 804.. 



trees, but it is not until about the middle of March, in the vicinity 

 of Washington, that those hatching succeed in escaping destruction 



and produce stem-mothers. In 

 fact, aphids from eggs hatched 

 before April 1 are sometimes all 

 killed by cold. The important 

 hatching, therefore, commences 

 after April 1. 



The young stem - mothers of 

 this species usually are abun- 

 dant upon the swelling apple 

 buds (fig. 9), and when these 

 begin to open the insects crowd 

 down among the bursting leaves. 

 By the time the stem-mothers 

 are adult — usually in about 13 

 days — many of the buds have 

 opened and the leaves expanded. 

 Each stem-mother produces 



Fig. 9. — The oat aphis : Young stem- 

 mothers clustered oo opening apple 

 bud. Much enlarged. (Original.) 



about 100 young, and these migrate 

 to the underside of the leaves, which 

 become coated with them. These 

 young may become either winged 

 (fig. 11) or wingless adults (fig. 10), 

 and at least four generations may 

 be produced upon the apple. The 

 wingless forms upon apple become 

 mature in about seven days, and 

 each individual produces about 75 

 young. The period of reproduction 

 lasts a little over two weeks, and 

 the insects live about a month. 



The winged forms produced upon apples become mature in a 

 little over 8 days and then fly to grains and grasses, as wheat, 

 oats, etc. 



Fig. 10. — The oat aphis (Aphis 

 iivcnuc) : Wingless agamic fe- 

 male, greatly enlarged, a. An- 

 tenna of same, still more en- 

 larged. (Davis.) 



