282 
Journal of Agricultural Research 
Vol. VIII, No. 7 
Length of pupae stage. —The pupal stage seems to vary greatly, 
depending upon temperature conditions of the season in which pupation 
occurs. Larvae which had hibernated through the winter went into pupa¬ 
tion as early as March, in California, and some of the hibernating larvae 
under less favorable conditions did not enter pupation until two or three 
months later. 
Fifty-two males reared from hibernating larvae showed an average of 
17.7 days in the pupal stage. Fifty-six females reared from hibernating 
larvae showed an average of 19.7 days in the pupal stage. In midsummer 
the pupal stage, as observed in the laboratory, showed an average of 6.5 
days. The shortest pupal period observed was 6 days, and the longest 
pupal period, not considering hibernation in that stage, was 35 days. 
ADULT 
Emergence. —The adult (PI. 78, C) upon emerging from the pupal 
skin finds itself completely inclosed within the walls of the alfalfa seed, 
which has been hollowed out by its host, B . funebris. It gnaws a small 
hole through the seed wall and through the seed pod, making its escape. 
Relative proportion op sexes. —In connection with the rearing of 
adults of this species from different localities throughout California and 
western Arizona, it was found that both sexes were well represented, but 
that the females were considerably more abundant than the males. A 
total of 1,249 adults examined showed 210 to be males and 1,039 to be 
females, or a ratio of 1 to 4.94. 
• SEASONAL HISTORY 
There are from two to four generations of this species in a single season, 
where conditions are favorable, as is the case in the alfalfa seed fields of 
central California. Under the less favorable, hot and dry desert condi¬ 
tions the species frequently has only a single generation in a season. .The 
development from egg to adult of each generation is completed within 
the unbroken alfalfa seed infested by its host. 
IMPORTANCE AS A PARASITE 
Tetrastichus bruchophagi is a parasite of considerable importance in 
controlling Bruchophagus funebris in the alfalfa seed-growing districts of 
central California, where it apparently destroyed about 52 per cent of 
the chalcis-fly larvae infesting alfalfa seeds in 1913. 
In the alfalfa seed fields of the Yuma, Ariz., district this parasite is 
apparently of little importance at the present time. Observations show 
that it destroys only about 1.5 per cent of the chalcis-fly larvae in that 
seed district. 
