99 Farmers’ Bulletin 1128. 
weather, and after the return of warmer weather continue their 
activities. Within two or three weeks after hatching the stem- 
mothers are mature and produce young. These later generations 
become adult usually in less than a week. Some of the insects so 
produced become winged while others remain wingless. 
The winged forms migrate to pepper-grass and other related 
plants and here they form colonies throughout, the summer. The 
number which migrate varies in different parts of the country. In 
some regions there is a very distinct and complete migration, while 
in other places the wingless forms remain. 
The wingless ones continue reproduction, and sometimes give rise 
to as many as 11 generations before the end of July. The numbers 
on cherry, however, gradually diminish, and during midsummer very 
Fic. 14.—The chokecherry aphis: Spring migrant. Much enlarged. 
few are seen upon the trees, and in some cases no insects can be 
found upon trees which earlier in the season were badly infested. 
During October fall migrants and winged males may be found 
returning to cherry trees and are often encountered during the 
migration period in larger numbers than might be expected. The 
fall migrants produce the egg-laying females which, when mature, 
are fertilized by the males. 
THE CHOKECHERRY APHIS.! 
The chokecherry aphis is found abundantly upon chokecherries and 
related trees. It is a pale green insect and is conspicuously mealy. 
The winged forms have a black head and body. 
The feeding habits of this species are very similar to those of the 
black cherry aphis. The leaves of the terminal twigs are attacked 
and twisted by the feeding of the insects, entire twigs sometimes be- 
ing destroyed. 
1A phis cerasifoliae Fitch. 
