296 



SCHOOL ENTOMOLOGY 



hibernated there over winter. As the foliage appears the 

 root aphides migrate to the new wood and upward to the 

 foliage where they feed and rapidly multiply. During the 

 summer all are wingless, reddish-brown females which are 

 covered with a white waxy secretion which forms a cottony 

 mass over the colony. In the course of a fortnight each 

 female gives birth to about 100 young, each of which becomes 



FIG. 213. The woolly apple-aphis (Eriosoma lanigera (Hausm.). 

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



o, agamic female; b, young nymph; c, last stage of nymph of winged aphis; 

 d, winged agamic female with enlarged antenna above all greatly enlarged and 

 waxy excretion removed. 



a full-grown female in eight to twenty days, and then in 

 turn gives birth to a similar number. Thus they increase 

 rapidly during the summer. Early in the fall a winged gen- 

 eration appears which migrates to elm trees. Each of these 

 winged females gives birth to from four to six wingless males 

 and females. These true sexes mate and the females each 

 lay a single egg in the crevices of the bark. The winter egg 



