266 



INSECTS AFFECTING SHADE TREES 



appearing in conspicuous and ^unsightly masses. It multiplies 

 parthenogenetically, like other species of the plant louse family, 

 during the summer, giving rise to winged migrants from time to 

 time. The sexual forms occur in the fall upon the maple, at which 

 time eggs are laid. The eggs are placed under loose bark "of the 

 silver and soft maples. There is a hibernating form which descends 

 to the ground and hibernates in rubbish, ascending the alders 

 again in the spring. 



Control. Kerosene emulsion is the best spray, since kerosene 

 readily penetrates the waterproof waxy secretion which covers 



FIG. 267. Cockscomb gall on white elm. 



the insects. Straw and leaves may be placed under the trees and 

 later gathered and burned to trap the hibernating forms. Infested 

 limbs should be cut off and destroyed as soon as noticed. 



The Cockscomb Gall. This species of louse (Colopha ulmicola 

 Fitch) causes a peculiar gall on elm leaves resembling a cock's 

 comb. In a general way the life history of this insect resembles 

 that of other aphids. The gall is about an inch long and one- 

 quarter of an inch high. The sides are wrinkled perpendicularly 

 and the summit irregularly gashed and toothed (Fig. 267). On 

 the under side of the leaf the gall has a slit-like opening. Upon 

 opening these galls, they are found to be crowded with lice and 

 white flaky material. 



