153 
base. The shell of these galls is very thin and the winged lice are 
found inside, in large numbers in September. The winged individuals 
Fig 1 . 28. 
have the veins of the wings arranged as in the preceding, but they 
are mnch smaller, and the antennae are only four-jointed. 
Gall of Pemphigus rhois. . 
Pemphigus ulmi-fusus. Walsh. The Red Elm Gall-louse. 
» x 
This is a very minute species, which forms a solitary, spindle-shaped 
gall about an inch long, upon the upper surface of the leaves of the 
red elm. The winged individuals measure only about one-fourteenth 
(0.07) of an inch to the tips of the wings, and are of a uniform dusky 
color. An occasional specimen has the third vein partially or fully 
forked, as in Eriosoma, thereby indicating a close relationship to that 
genus. 
Pemphigus popularia, Fitch. Poplar Gall-louse. 
A species noticed by Dr. Fitch, wandering up’ and down the trunk 
of the balsam poplar, whose habits are yet unknown. It closely re¬ 
sembles the preceding, but its abdomen is green; its antennae quite 
short, reaching but two-thirds the distance to the insertions of the 
wings; the rib-vein not widened along the stigma; length to the tip 
of the wings about one eighth of an inch. Color black, slightly 
dus'ed over with a white powder; the abdomen dull green, with a 
coating of white flocculent down; sides parallel; wings dull hyaline; 
the rib-vein black. 
Pemphigus populi-globuli, Fitch. The Poplar-bullet Gall-louse. 
This species produces a green gall about the size of a bullet, globular 
in shape, on the leaves of the balsam poplar. These galls are situated 
slightly above the base of the leaf, projecting from the upper surface, 
