222 Trans. Acad. Sci. of St. Louts 
Parasitic Hymenoptera. 
Chalcid parasites, Monodontomerus sp. [J. C. Crawford]. 
When the observations began on June 25, 1917, and 
the Anthophora bees, etc., first appeared that spring, 
hundreds of these parasites were at once on hand. Their 
emergence was almost simultaneous. The number on 
this first day of my visit was so great as to make me 
fear the appalling mortality that must be in store for 
their hosts, the bees, even if only a small portion of 
them were to be permitted to beget offspring. They 
were actively searching over the bank, entering burrows 
and dancing before the bank in the bright sunshine. 
I could then get direct evidence only that they had come 
from the cocoons of Anthophora abrupta, but they were 
undoubtedly parasitic upon other species as well, since 
they were found at the bank also in the fall, and the 
bees, A. abrupta, ended their life cycle in July. One 
burrow of the mining-bee, when opened, exposed to 
view fifty Monodontomerus adults; I could not be ab- 
solutely sure, however, that all of these were young 
parasites just emerging from this cell; it is possible 
that some of the sun-dancers had left their companions 
and crowded into this cell of mixed sexes. In 1920, on 
July 24, 13 cells of this Anthophora bee were taken into 
the laboratory, only four of which proved to be infected 
by this parasite. These four cells gave forth 139 adult 
parasites, 109 of which were females and 30 males, or 
an average of about 35 for each bee cell. At such an 
alarming rate of increase, it is surprising that any bees 
at all should have escaped them. 
These parasites throve and appeared in large num 
bers in each of the seasons of observation. There 1# 
