THE VAGABOND GALL LOUSE 



271 



ish cocoon and attaches it to a tree or a fence or the side of a build- 

 ing or a vine. A wingless female (Fig. 275) emerges therefrom in 

 the spring and lays eggs in masses upon the silk of the cocoon. 

 These egg-masses are covered with a white, frothy substance so 

 that the individual eggs are obscured. They commence to hatch 

 in a few weeks and continue until early summer, when some of 

 the first hatched caterpillars begin to pupate. The moths from 

 these pupse give rise, in some latitudes, to a second generation, 

 which passes the winter as pupse. 



Injury. This caterpillar is sometimes extremely destructive 

 to the foliage of fruit and shade trees, and has been known to eat 

 holes in the fruit of the apple. The destructive work of this insect 

 is well shown in figure 276. 



FIG. 275. Wingless female of the white-marked tussock moth. (Houser, Ohio Bull., 194.) 



Control. Egg-masses should be destroyed when pruning the 

 trees. If infestation is serious in any locality, trees may be banded 

 with tanglefoot or any sticky substance to prevent the ascent of 

 ohe larvae. Arsenical spraying when the larvae are hatching catches 

 the first brood. 



Fortunately this pest is subject to the attacks of numerous 

 parasites which have been at times a means of preventing serious 

 injury. 



The Vagabond Gall Louse (Pemphigus vagabundus Walsh). 

 This insect forms unsightly galls on the cotton woods, but 

 deserts these trees before the latter part of summer. The galls 

 may be seen on the tips of twigs and become perfectly black when 

 old. They do not seriously affect a tree's functions unless they 

 occur in great numbers. 



