Feb. 21, I9l6 
Green Apple Aphis 
991 
most of the unfertilized females were observed to produce some sterile 
eggs, frequently laying the entire 6. 
During the fall of 1914, eggs were first observed on the trees at Vienna, 
Va., on September 29. These were newly laid, being still yellow in 
color. 
SUMMARY OF LIFE HISTORY 
The life history of Aphis pomi may be briefly outlined as follows: The 
egg is laid upon the tender twigs of the apple, though occasionally it is 
laid upon the bark of the older twigs. It is light yellow when laid, but 
later changes to shining black. Development for a few days is very 
rapid, after which the egg rests for the winter. When the revolution of 
the embryo is completed in the spring, an increase in temperature will 
cause the egg to hatch. Before this revolution a high temperature only 
tends to destroy it. Early in April the egg hatches by a uniform splitting 
over the insect’s head. 
The stem mother is wingless and becomes mature in about 10 days. 
She produces summer forms, both winged and wingless, with the winged 
ones predominating. There are 9 to 17 generations of the summer forms 
at Vienna, Va. After the second generation the wingless forms always 
outnumber the others, but winged forms may occur in every generation. 
They become rare toward the end of the season. On the other hand, a 
wingless line may be carried from the stem mother to the egg. A third 
form, the intermediate, may occur throughout the summer. 
The wingless sexes begin to appear about the 1st of September. They 
occur in all generations, from the eleventh to the nineteenth, inclusive, 
and probably also in the ninth and tenth. 
The summer wingless forms and the oviparous females, which live 
longer than the males, remain on the trees at Vienna, Va., until the 
leaves drop, usually about the middle to the last of November. 
Mating commences toward the close of September, one male usually 
serving more than one female. Both sexes feed. The oviparous female 
may lay infertile eggs if not reached by a male, and these eggs do not 
become black. The fertile egg develops to the resting stage before the 
first heavy frosts; otherwise it may be winterkilled and will not hatch 
to a stem mother the following spring. 
GENEALOGICAL DIAGRAM 
The accompanying diagram (fig. 4) shows the number of lines possible 
from one stem mother as indicated by the writers’ breeding experiments. 
A line from each form reproduced in any given generation from known 
parents was carried until the sexual forms appeared. In some cases 
the lines indicated either died or were lost. The former are shown by a 
short transverse line (-) and the latter by (?). It will be seen from the 
chart that one direct wingless line was obtained from the stem mother 
