Aphids Injurious to Orchard Fruits, Etc, 11 
The young stem-mothers of this species usually are abundant upon 
the swelling apple buds (Pl. IV, A), and when these begin to open 
the insects crowd down among the burst- 
ing leaves. By the time the stem- 
mothers are adult—usually in about 13 
days—many of the buds have opened 
and the leaves expanded. [ach stem- 
mother produces about 100 young, and 
these migrate to the blossoms and to the 
underside of the leaves, which become 
coated with them. (PI.IV,D.) These 
young may become either winged or 
wingless adults (Pl. IV, E, F), and at 
least four generations may be produced 
upon the apple. The wingless forms 
upon apple become mature in about 
seven days, and each individual produces 
about 75 young. The period of repro- 
duction lasts a little over two weeks. 
and the insects live about a month. 
The winged forms produced upon ap- 
ples become mature in q little over 8 
days and then fly to grain and grasses, 
as wheat, oats, etc. (Pl. IV, G, H, 0.) 
In the autumn migrants are produced 
on grains. (PI.IV,L.) These mature in 
about 2 weeks and return to the apple, 
the migration lasting 3 or 4 weeks, since 
not all the migrants are produced in the 
same generation. (Pl. IV,J, L.) During 
their life of some 6 weeks these migrants 
produce about 5 egg-laying females each. 
The winged males are produced upon 
the summer food plants and migrate to 
the apple leaves to mate with the sexual 
females. (Pl. IV, M, N.) After the 
female has become fertilized she deposits 
her eggs in crevices of the bark of the 
larger branches or behind the bud scales 
of the young twigs of the apple. (Fig. 
6.) The length of life of each sex de- 
pends upon weather conditions. This 
is particularly true of the female, which 
sometimes lives for weeks in a more 
Fic. 5.—The green apple aphis: Winter 
eggs onapple twig. Much enlarged. 
or less dormant state during cold weather. In warm climates the 
species may hibernate as wingless females upon the summer hosts. 
