Aphids Injurious to Orchard Fruits, Etc. 15 
SEASONAL HISTORY. 
The eggs of this insect are laid in the fall upon the twigs of the 
quince, and the stem-mothers hatch in the early spring. By early 
summer the insects are abundant and winged forms are being pro- 
duced. This production of winged forms, or migrants, continues 
until late summer. The migrants fly from their winter hosts to 
clovers and peas and produce numerous generations on these plants 
in a manner very similar to that of the clover aphis. In the fall, 
migrants are produced which return to the quinces and produce the 
ege-laying females, which after mating with the males deposit the 
winter eggs. The flight of the insects from clover begins in Septem- 
ber and extends throughout October. 
PEAR APHIDS ATTACKING THE FOLIAGE. 
Several species of aphids are found upon pear foliage. Most of 
these, however, occur also upon other trees and are treated elsewhere 
in this bulletin. The more common forms upon pear are the green 
apple aphis, the apple-grain aphis, and the clover aphis. 
Another species, the woolly thorn aphis,'! is common in some locali- 
ties. Both winged and wingless forms are covered with a white, 
waxy substance. The wingless forms are pale green and the winged 
forms have a black head and body. The insects hatch in the early 
spring and soon attack the leaves, curlmg and twisting them. Dur- 
ing early summer the winged forms leave the pear tree. In the fall 
migrants may be found again, and these produce the sexual forms, 
the females of which lay their eggs upon the bark. Besides attacking 
pear, this species occurs upon thorn, quince, and Juneberry. 
Two other forms are found commonly upon pear, but these occur 
upon the roots, and since they are seldom found upon the branches 
and foliage and require different remedial measures, they are not 
treated in this bulletin. The first of these is the woolly pear aphis,’ 
which is common in the western part of the country, and the second 
is Fitch’s pear root-aphis,? which is very similar to the woolly thorn 
aphis and occurs in the eastern United States. 
PLUM APHIDS. 
Three or four species of aphids are common on the plum, two of 
which are, during some seasons, very injurious. Many complaints 
of injury to Japanese and native plums by the rusty plum aphis have 
come from the more southern States, while the mealy plum aphis is 
more often prevalent in the North and West, on Domestica, or the 
European type of plums. The hop aphis, according to records of the 
Bureau of Entomology, has not occasioned much injury to plums in 
recent years, although in the Pacific Northwest it continues to be a 
pest of importance to hops. 
1 Prociphitus corrugatans (Sirrine). ‘Eriosoma pyricola B, & D. 8 Prociphilus fitchiB. & D. 
