1965] 
Creighton and Nutting — Cryptocerus 
61 
fashion, for there was no noticeable difference between their behavior 
and that of the Tucson colony. This colony was housed in a plastic 
petri dish 90 mm. in diameter. A short polyethylene tube connected 
this petri dish to a second one which served as a feeding chamber. 
This arrangement permitted a close watch on the development of 
the brood. The other two colonies were kept in sealed aquaria which 
contained oak block observation nests. This provided the ants with 
passages similar to those which they normally use and at the same 
time gave them the opportunity to forage outside the nest. 
Most of the habits of rohweri are like those of texanus but there 
are some significant differences in the behavior of the two species. At 
maturity the rohweri colony is notably smaller than that of texanus. 
There are seldom more than seventy-five workers present and in most 
of the colonies that we have seen the total has been less than fifty 
individuals. This is undoubtedly due to the fact that rohweri is 
seldom, if ever, pleometrotic. Each of the nine colonies of rohweri 
which we have examined had a single queen. The nests of rohweri 
are established in abandoned burrows of wood-boring beetles (often 
those of small buprestids) which are cleared of the detritus left in 
them by the beetle larvae. While most of the branches selected by 
rohiveri consist of hard, sound wood it will nest in rotten branches 
as well. A limb housing one of the Santa Catalina colonies was so 
badly decayed that the ants were extracted by crumbling the wood 
between the fingers. As shown elsewhere (4) texanus ordinarily 
rejects nest sites in rotten wood. The burrows chosen by rohweri are 
of a size that permits the major to occlude the terminal opening. This 
occlusion is like that of texanus; the opening is blocked by the head 
and pronotum of the major, who crouches to admit the minor. An 
interesting variation of this response was observed in the junior 
author’s colony. This colony originally occupied burrows in a large, 
dead palo verde branch. Just inside the entrance of one of these 
burrows was a circular flange of detritus. The circular opening in 
this flange was slightly more than 2 mm. in diameter. This opening 
was occluded by the cephalic disc of the major, who stood in the 
passage behind the flange. The workers of rohweri pack themselves 
tightly into the outer portion of the nest passage, as do those of 
texanus, but show one response under these conditions that texanus 
does not display. The minor worker of rohweri can reverse its 
position in the passage by a twisting somersault. This begins with a 
lowering of the head, whose forward edge is thrust under the anterior 
coxae. Thereafter the body is swung forward and downward and 
during this arc it is twisted sidewise. The end result is that when the 
