Field Studies of the Non-Social Wasps 415 
after nidification, divorce each other and find new mates 
with the beginning of a second brood? One may specu- 
late for hours on how the house-hunting and removal 
may oceur, when one lucky chance of being on the scene 
at the right time may clear up all the mystery in a half 
hour. 
There are at least two generations of T. clevatum per 
year, the first generation in June, as I have recorded 
them here from the clay bank and from the cells of the 
mud-daubers’ nests, and the second in later summer, 
having emerged as adults in August. 
The members of this species, as I have stated early in 
this chapter, select whatever ready-made homes they 
ean find, the old cells of the mud-daubing wasps, (fig. 54 
shows a section of a Sceliphron nest; ‘‘a’’ has the cocoon 
and debris in situ, and ‘‘b’’, removed to show the mud 
partitions), holes in posts and logs, etc. These she di- 
vides into rooms by partitions of mud which she carries 
from afar. In using the old cells of mining bees, her 
method is hardly different. One nest contained seven 
cells, as illustrated (fig. 55B). The burrow was %4 inch 
in diameter, 3 inches long, with a branch 1% inches in 
length. The opening was plugged with mud, and the two 
first small cells were empty. I always found one or two 
cells near the entrance empty; these I called, for want of 
a better name, air-chambers. The next five cells con- 
tained spiders and eggs or larvae. The contents of the 
first cell were lost, but the second one had ten spiders and 
® young larva; all spiders were apparently dead, since 
none responded to stimulus, but all were plump and 
fresh. The next cell contained nine spiders, which also 
were freshly killed, and only one gave very slight re- 
sponse to stimulus. A very small larva was attached to 
one of the spiders. The fourth cell had ten freshly- 
