Aphids Injurious to Orchard Fruits, Etc. 37 
causing the berries to drop. It can be distinguished easily from any 
other forms occurring on the grape by its large size and its dark- 
brown color. 
SEASONAL HISTORY. 
The eggs of this species are laid upon the twigs of the black haw.* 
Very early in thespring they begin hatching,but thesefirst stem-mothers 
may be killed by frost. Six or 
eight weeks later the aphids of 
thesecond generation mature, 
and these nearly all become 
winged. These migrants fly to 
the grape and produce young 
upon the tender growing shoots, 
where in less than 10 days they 
are mature and producing | 
young. Reproduction on the | 
grape continues throughout the 
summer, and often more than 
a dozen generations may occur. - 
In -each: generation winged 
forms are found and_ these 
carry the infestation to new 
vines. During October fall 
migrants are produced, which 
return to the haw trees and 
deposit the egg-laying females. 
When mature these are ferti- 
lized by the winged males which 
follow the fall migrants, and 
egg laying results. 
NATURAL ENEMIES OF 
APHIDS. 
Aphids are attacked by va- 
rious species of parasitic and 
predacious insects and by 
fungous diseases, and _ these 
agencies exert a very impor- _ — 
tant influence in their control. Fic. 28.—The grapevine aphis: Colony on grape shoot. 
The combined effect of these several factors normally keeps the aphids 
pretty well reduced, but when for any reason their activities are 
lessened the aphids may increase enormously and do widespread 
injury. Heavy driving rains are believed to be inimical to aphids, 
a 
1Viburnum prunifolium. 
