198 ' Trans. Acad. Sct. of St. Louis 
Trypoxylon clavatum Say. [S. A. Rohwer]. 
This species of wasp in which the male parent guards 
_ the nest while the female hunts, has been recorded as 
making use of old beetle burrows in logs, and cleaning 
out and using the old cells of the mud-dauber wasps. In 
the clay blank, they were quite abundant, here using the 
empty bee burrows, partitioning them with mud and 
filling each compartment with spiders. 
When this species first made its appearance in 1917, 
about June 28, there were only three nests, each with its 
male guarding the doorway, and four days later there 
were seven. By the time of the next visit, on July 16, 
these had vanished, and for two weeks not a single 
T. clavatum was to be found. On July 31, the first one 
of the second generation appeared. Time dragged on and 
this one continued to be the sole representative of the spe- 
cies. Not until the first of September did others appear, 
and during that week a half-dozen or more were at work. 
During the latter half of that month, they succumbed to 
the inevitable. While 7. clavatwm appeared in the fol- 
lowing years, their numbers became fewer; the species 
was not holding its own. No doubt one very consider- 
able factor in the reduction of their numbers was the 
destruction I wrought in digging up their nests when 
their colony was not yet strong, in order to study their 
prey. 
The relation of these insects to the unit was pri- 
marily in using the old burrows; with the male on guard 
in each nest it is not likely that the young of this wasp 
serves as host to any parasites. A comparison of the 
contents of their nests with the list of spider inhabitants 
of the clay bank shows that they must have gone afield 
