PLANT LICE 



Since special cases are always more convincing than 

 general statements, let us follow the seasonal history of 

 some particular aphids, taking as examples the species 

 that commonly infest the apple. 



Let the time be a day in the early part of March. 

 Probably a raw, gusty wind is blowing from the north- 

 west, and only the silver maples with their dark purplish 

 clusters of frowzy flowers already open give any sug- 

 gestion of the approach of spring. Find an old apple 

 tree somewhere that has not been sprayed, the kind of 

 tree an entomologist always likes to have around, since 

 it is sure to be full of insects. Look closely at the ends 

 of some of the twigs and 

 you will probably find a 

 number of little shiny 

 black things stuck close 

 to the bark, especially 

 about the bases of the 

 buds, or tucked under the 

 projecting edges of scars 

 and tiny crevices (Fig. 

 91). Each little speck is 

 oval and about one thirty- 

 sixth of an inch in length. 



To the touch the ob- 

 jects are firm, but elastic, 

 and if you puncture one a 

 pulpy liquid issues from 

 it; or so it appears, at 

 least, to the naked eye — ■ 

 a microscope would show 

 that in this liquid there is 



organization. In short, the tiny capsule contains a young 

 aphid, because it is an aphid egg. The egg was de- 

 posited on the twig last fall by a female aphis, and its 

 living contents have remained alive since then, though 

 fully exposed to the inclemencies of winter. 



[157] 



Fig. 91. Aphis eggs on apple twigs in 

 March; an enlarged egg below 



