410 Trans, Acad. Sci. of St. Louis 
ing the time between the last of the first generation and 
the first of the second generation. At the time of their 
discovery, three nests were found, all containing guards. 
Two of the apertures were small enough to nicely fit the 
head of the male watcher; the third was entirely too 
large, and the little head looked comically lost in the cav- 
ernous hole over which it kept solemn guard. This male 
evidently realized his condition, if one may use such 
terms, and would not put his head to the opening as did 
the others, but remained on guard an inch or so within 
the burrow, where his comical triangular face could be 
seen. In one of the other nests, the silvery face of the 
male could be seen at the orifice for hours, keeping out 
intruders, although the only impostors that seemed to 
bother were members of its own species. The female, of 
course, is usually out foraging for spiders or getting mud 
for the partitions while the male is busily at rest. These 
wasps move with stiff, angular, jerky movements, and 
often poise in the air like a hummingbird for several sec- 
onds before entering the nests. Often the female will 
rest for several seconds at the opening, shaking antennae 
as if communicating with the door-keeper. This may be 
a secret sign, for then out he comes, mounts her back, 
and thus they enter. Sometimes the smallness of the 
aperture forces him backward, but he clings as best he 
ean. In all of the nests observed, a male was always on 
guard; this was in contrast to T’. texense, observed by 
Hartman where the male was only occasionally present. 
For three days I had the opportunity of watching one 
nest of T. clavatum very closely, while waiting for the re- 
turn of some bees that had been taken out in homing eX- 
periments. During this time, this male did not once leave 
the burrow; he stood guard bravely, and often assisted 
the mother by relieving her of the spider as she reached 
