CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS 1 45 



Hop Plant-louse {Phorodon humuli Schrank). — Migrates from plums 

 to hop in the third generation; yellowish-green, with a prominent 

 tubercle on head at base of each antenna, and another smaller tubercle 

 on the base of each antenna. 



Apple Woolly Aphis {Schizoneura (= Eriosoma), lanigera Haus, 

 americana Riley in part). — (Consult Bull. 256, Maine Agr. Expt. Stn., 



Fig. 97. — Forms of the woolly apple aphis: A, winged viviparous female; 

 B, stem-mother; D, wingless viviparous female, summer form; E, male; F, pupa 

 of fall migrant; G, oviparous female. All much enlarged. {After Baker, U. S. Bur. 

 Ent.) 



1916.) This native woolly aphis is frequently injurious to many vari- 

 eties of apple trees, causing deformations both on the stems and leaves 

 and on the roots. It occurs also on pear, hawthorn and mountain 

 ash, and passes part of its hfe on the elm. The injury to the roots 

 consists in the formation of hard fibrous enlargements resembling 

 knots or clubs, often causing the death of the affected part. Nursery 



