103 



it lives uudei- ground at all seasons of the year it comes 

 to infest more or less generally the soil itself, although 

 this may be cleared of it by a few months' thorough cul- 

 tivation sulticient to destroy etfectively all living apple- 

 roots. Like many other plant-lice, the woolly aphis mul- 

 tiplies throughout the greater part of the year by the 

 birth of living young from generations of wingless fe- 



Fig. 8. — Woolly Aphis (Schizoneura lanigera.) — a, root of young 

 tree illustrating deformation; b, section of root with aphides clus- 

 tered over it; c, root louse, female — a and b, natural size; c, much 

 enlarged. (Marlatt, U. S. Dept. Agr.) 



males only, but in October or November winged females 

 appear somewhat abundantly, and, flying freely, espec- 

 ially before the wind, distribute the species widely. 

 From these descend in the same autumn a generation 

 of males and females, the latter of which eventually lay 

 each a single winter egg. This is commonly placed 

 within a crevice of the bark, and, hatching in spring, 

 give rise to a new colony. There may be more or less 

 migTation back and forth from the groups above ground 



