6 
Considering the inefficiency of natural agencies, if we except atmos- 
pheric conditions, in the control of this pest, it is hoped that a com- 
mon fungous disease of aphides, known as Hmpusa aphidis, may become 
an important factor. As the development of this fungus is dependent 
upon rather warm, humid weather and is retarded by drought, it is 
fairly certain that atmospheric conditions, after all, are most important 
in the limitation of this insect. It is within the bounds of possibility 
that the fungus might be cultivated artificially and be used during 
weather conditions favorable in the control of this pest. 
Ke qpaserentiers 
Fig. 3.—A lace-wing fly (Chrysopa oculata): a, Eggs; 6, full-grown larva; c, foot of same; d, same 
devouring pear-tree psylla; ¢, cocoon; f, adult insect; g, head of same; h, adult. All enlarged 
except h, which is natural size. (From Marlatt.) 
METHODS OF CONTROL. 
In some instances natural enemies of the pea aphis have rendered efti- 
cient service. Seldom, however, do they destroy the insects early enough 
in the season to save a crop. In the course of time—many years in all 
likelihood—these enemies may become more effective; hence, in view 
of the fact that the extermination of the species even in a limited area 
is a practical impossibility, anything that can be done to destroy the 
aphis without harming its insect enemies is advisable. If this can be 
accomplished it will afford in itself a reason for the rejection of insecti- 
cides, none of which is in all respects satisfactory.! 
1 For the benefit of some persons who are not wholly familiar with the feeding 
habits of this species it should be stated that it obtains nourishment by suction, 
and can not therefore be reached by means of internal or stomach poisons such 
as Paris green and other arsenicals. 
A6——+49 
