54 



THE MONTHLY BULLETIN. 



Life History. — The stem mother starts the peculiar gall on the stem 

 at the base of the leaf, and produces young until the large gall is com- 

 pletely filled. So tightly closed is the entrance of the gall that few, 

 if any, parasites get in. When the inhabitants are ready to migrate 

 in the late summer a distinct opening is made, through which they 

 escape in great numbers. 



Fig. 43. — Galls on cottonwood leaves produced by the poplar-stem 

 gall-louse (.Pemphigus popuUcauUs Fitch). (Essig, P. C. Jr. Ent. ) 



Distribution. — Throughout the State, wherever the host plants are 

 found. 



Food Plants. — Common cottonwood (Populus trichocarpa) , P. monili- 

 fera and L\ tremuloides. 



Natural Enemies.— Preyed upon by internal parasites in late sum- 

 mer, but more often the food of a small bug belonging to the family 

 Acantltiiche. 



