THE MONTHLY BULLETIN. 



55 



Fig. 44. — Cross-section of 

 (Essig, P. C. Jr. Ent.) 



?alls, showing all stages of the lice inside. 



THE BEAD-LIKE COTTONWOOD GALL-LOUSE. 



Pemphigus populimonilis Riley. 

 (Figs. 45, 46.) 



General Appearance. — The body is dark and covered with rather 

 long white flocculence, which gives it a bluish appearance. The 

 presence of the lice is easily told by the very characteristic reddish, 

 bead-like galls formed on the margins and centers of the leaves of the 

 Cottonwood trees which they infest. 



Life History. — The female louse or stem mother either deposits the 

 eggs or brings forth offspring which give rise to the spring genera- 

 tions. There is usually but one winged female to be found in each 

 gall, but often there are also present several larvae of a syrphid fly, 

 which feed upon the lone occupant. For this reason many of the galls 

 will be found empty during the later summer months. However, in 



