PLANT LICE 



early part of the season the individuals of this species 

 are found particularly on the under surfaces of the apple 

 leaves. They cause the infested leaves to curl and to 

 become distorted in a characteristic manner (Fig. 96). 

 The stem mothers (Fig. 97 A, B) begin giving birth to 

 young (C) about twenty-four hours after reaching ma- 

 turity, and any one of the mothers, during the course of 

 her life of from ten to thirty days, may produce an aver- 

 age family of fifty or more daughters, for all her offspring 

 are females, too. When 

 these daughters grow up, 

 however, none of them is 

 exactly like their mother. 

 They all have one more 

 segment in each antenna; 

 most of them are wing- 

 less (D), but many of 

 them have wings — some, 

 mere padlike stumps, but 

 others well developed or- 

 gans capable of flight 

 (Fig. 97 E). 



Both the wingless and 

 the winged individuals of 

 this second generation are 

 also parthenogenetic, and 

 they give birth to a third 

 generation like them- 

 selves, including wing- 

 less, half-winged, and 

 fully-winged forms, but 

 with a greater propor- 

 tion of the last. From 

 now on there follows a 



large number of such generations continuing through the 

 season. The winged forms fly from one tree to another, 

 or to a distant orchard, and found new colonies. In 



[163] 



Fig. 96. Leaves of apple infested and 



distorted by the green apple aphis on 



under surfaces 



