420 
Psyche 
[December 
the biology of the blowflies that are used as prey. Dr. K. R. Norris 
informs us {in litt.) that the males of Calliphora tibialis resemble 
those of some of the carrion calliphorids in exhibiting intense activity 
from just before dawn until at most an hour afterward. Each male 
selects a perch from which it flies off periodically to challenge passing 
insects. Dr. Norris believes that this may be an instance of terri- 
toriality, as males often appear on the same perch time after time 
and may engage in aerial combat with neighboring males. The 
females, on the other hand, do not exhibit this behavior and are 
usually to be found on the ground or moving about from place to 
place. Thus the males would be especially available to a wasp capable 
of attacking in the early morning hours, especially if the males 
challenged approaching Sericophorus. 
It is possible, too, that there is a selective advantage in the wasps’ 
use of males. The females are ovoviviparous, and might deposit 
maggots in the cells which could destroy the wasp egg or larva, as 
sometimes occurs in Bembix (Evans, 1957, p. 77). C. tibialis 
happens to be specific to earthworms, so it is improbable that its 
maggots would attack wasp larvae. However, it is probable that 
other calliphorids are used in numbers at other times and places, 
and these may be capable of doing so. 
The hunting activities of Sericophorus must have a tremendous 
impact on the host fly populations. Estimating conservatively, over 
50,000 male C. tibialis are captured and entombed by the colony 
behind C. S. I. R. O. in a single season (i.e., 100 active nests 
X 100 days X 5 flies per day per wasp) ! Such an apparent high 
degree of host specificity is possible only when the prey are con- 
tinuously available and themselves maintain relatively large popu- 
lations. 
During transport, the fly is held venter up and grasped near its 
wing base by the wasp’s hind legs only (Figs. 5, 6). The sting 
was never observed to be used for holding the fly. The wasps’ 
flight is swift and noiseless, the females reappearing suddenly. 
Typically the prey-laden wasp lands on the edge of her nest 
mound and quickly plunges into the open entrance; rarely she lands 
on the ground nearby and walks to her nest. Walking is done in a 
somewhat jerky manner, the wings held flat over the body, with no 
flicking. During the period of active provisioning, several trips for 
prey are made in rather rapid succession, with little time spent in 
the nest between trips. Whereas in S. victoriensis two or more 
adults are reported to utilize the same nest (Rayment, 1955a), this 
was never observed in S. viridis. The females appear to spend the 
