THE PEA APHIS WITH RELATION TO FORAGE CROPS. 27 
to control, or at least hold in check, the aphides, and a little later, 
usually depending on the climatic conditions, the aphidid fungus 
{Empusa apJiidis) becomes prevalent, so much so, in fact, that the 
plant-lice are often apparently completely exterminated. However, 
as the weather conditions become more favorable for the apliis and 
less for the fungous disease and the aphidid parasites, the few sur- 
vivors are soon able to cover the plants with their progeny, so that 
by September we ordinarily find them again abundant on clover and 
late garden peas. 
Farther north the insect does not seem to appear in injurious num- 
bers until later — that is, not until about July. The following records 
of injury for 1899 recorded by Dr. Chittenden (1900) illustrate this 
statement. The first record was for Gloucester County and Ports- 
mouth, Va., on May 17; Maryland, May 23; Newark, Del., June 2; 
East Hampton, Conn., July 3; Long Island, N. Y., July 7: Orono, 
Me., July 28; Ontario and Xova Scotia, Canada, August 9. 
GENERATION EXPERIMENTS. 
We have carried on generation experiments with this species 
through two years (1912 and 1913) at La Fayette, Ind., and the fol- 
lowing notes were made at La Fayette, except as indicated. The 
same general methods, as well as the cages and rearing shelters, here- 
tofore used by the witer and described and figured in Technical 
Series Bulletin No. 25, Part II, of the Bureau of Entomology, have 
been adopted. The ^vriter here expresses his appreciation of the 
services rendered by Messrs, C. W. Creel and A. F. Satterthwait, both 
of the Cereal and Forage Crop Insect Investigations, who attentively 
cared for the experiments during the absences of the writer in 1912 
and 1913, respectively. 
In 1913 eggs began to hatch on March 31 and from that date until 
January, 1914, there was obtained, out of doors, a maxmunn of 19 
generations, no sexual forms being produced in the first-born genera- 
tion series. On the otlier hand, following down " the last-born of the 
last-born" generation series, a minimum of 7 generations was obtained, 
the last generation consisting of males. The last generation^ in tliis 
case, was really the twelfth generation from the egg, for a break in 
the first series of last-born generations made it necessar\' to substi- 
tute with tlie last-born of a later generation. Thus we obtained an 
average of 13 generations for the year. (See Table II.) 
