584 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



time. They are not usually detected until they have multiplied 

 sufficiently to make small white patches on the hark or leaves 

 which look like mold. During the spring and summer all are wing- 

 less females, not over one-tenth inch long, of a reddish-brown 

 color and covered with a white, waxy secretion, given off in threads 

 from the abdomen so as to form a cottony mass over the colony. 

 These females produce' from 2 to 20 young per day, which 



FIG. 440. The woolly apple-aphis: at left, colonies on twig and in scar 

 on an apple limb; at right, crown and root of young apple tree, showing 

 characteristic swellings produced by the root aphides. (After Alwood.) 



become full grown in from eight to twenty days according to 

 Alwood,* 100 or more probably being produced in two weeks. 

 Reproduction continues on both tops and roots except as checked 

 by the cold of winter, the aphides becoming most abundant in 

 midsummer. Early in the fall a generation of winged aphides 



* Bulletin 45, Va. Crop Pest Commission, p. 12, Special Bulletin, Va. 

 Agr. Exp. Sta. 



