40 THE COLORADO EXPERIMENT STATION 
leaves of plum and prune trees. It often is so numerous that the 
under leaf surface is completely covered by the lice. 
The stem-mothers hatch from black shining eggs deposited 
upon the twigs of the trees late in the fall. They locate upon the 
underside of young growing leaves where they give birth to a 
large number of living young which, so far as we have observed, 
do not acquire wings. At Austin, Colorado, May 22, ’08, many of 
the second generation were mature and producing young. In the 
earlier sections this louse becomes very abundant by the loth to 
the 15th of May and may continue to about the 15th or 20th of 
July when nearly all will have acquired wings and left the trees. 
About Fort Collins, at least, we find that occasional colonies of 
this louse remain upon plum trees throughout the summer. 
Upon leaving the plum, the lice go to certain grasses to feed 
during the summer. We have specially found it infesting Reed- 
grass, Phragmites Phragmites, on wet ground and along ditches 
upon the western slope in Colorado. 
About the middle of September* the fall migrants begin to 
return to the plum trees and to give birth to the sexual males and 
females. The males are winged and the females wingless. The 
latter deposit the eggs that remain over winter. 
This louse may be easily distinguished from other plum infest¬ 
ing species by its light green color, with three longitudinal darker 
stripes above, the white powdery covering to the body, the long 
narrow body, the short cornicles, and the small second fork in the 
third sector of the fore wing. The leaves when loaded with this 
louse,' may drop and become yellow but they do not curl as is so 
often the case in plant louse attacks. 
REMEDIES 
The lice will leave of their own accord by about July 10 in 
the warmer portions of the state and a little later in other sec¬ 
tions. If found very abundant before July ist, it will doubtless pay 
to make a thorough spraying with kerosene emulsion or Black 
Leaf as recommended for the green apple aphis. 
This louse seems to have few natural enemies to keep it in 
check. ■ 
THE HOP -PLANT LOUSE 
{Phorodon hiimidi Schrank) 
This is another green louse that inhabits the plum as a winter 
host plant. This louse is specially noted for its severe injuries to 
the hop during the summer months. It is generally distributed in 
the state and has frequently been taken by us upon both cultivated 
* September 16, 1906, is our earliest date for return migrants to the 
plum. 
