166 PLANT LICE. 
The lice are covered with a large amount of flocculent matter, 
and they also exude an abundant supply of honey-dew. 
P. rhois Fitch (The Sumach Gall-louse) makes a smooth, 
thin-walled gall on the under side of the leaf of the sumach, 
usually near the base of the leaf (Fig. 146). These remarkable 
galls, sometimes rather appetizing by resembling a small and 
brilliantly colored apple, are crowded with insects. ) 
P. rubi Thos. has been found on the under side of the com- 
mon raspberry along the mid-vein. 
While printing this report a copy of one of Prof. Forbes’ 
excellent bulletins was received, in which he describes the insects 
infesting the sugar beet in Illinois. Among other insects injuri- 
ous to that plant he describes also a plant-louse destructive to 
the above plant. 
CU 
Fic. 146—Pemphigus rhois Fitch. After Riley. 
Pemphigus bete Doane. (The Beet Aphis). 
This insect, but recently discovered by Mr. Doane of the 
Washington State Agricultural Experiment Station, at Pullman, 
Wash., offers an extraordinary example of the injury to vegeta- 
tion which may be caused by root-lice. Mr. Doane writes, that 
“when it was found a field of two or three acres of beets was 
generally infested, a strip of twenty-five to a hundred yards being 
so badly injured that the beets were nearly all soft and spongy, 
and the plants much smaller than the average.” The same in- 
sect also infests such weeds as the wild yarrow and a common 
knot-weed, as well as other plants and grasses. It occurs in 
two forms, winged and wingless, as shown in Fig. 147, of which 
