1960] 
Evans — Bembix u-scripta 
59 
Oviposition and development are as described for the Texas colony. 
Invariably provisioning occurs until the larva is nearly ready to spin 
its cocoon. 
Summary and Discussion 
Despite the difference in season and ecological situation, the mem- 
bers of the two colonies studied exhibited striking resemblances in 
nesting behavior. The slightly deeper nests of the New Mexico colony 
were doubtless correlated with the lighter texture of the soil. As a 
general rule, with reference to populations of a single species or closely 
related species, wasps nesting in looser soil tend to make deeper nests. 
In this instance the difference in nest depth is slight, and it would be 
rash to claim that it is genetically determined. The fact that the New 
Mexico colony was much smaller and had the nests much more widely 
scattered may merely mean that this area was ecologically marginal 
for the species or that this population had undergone a decline because 
of unknown physical or biological factors. 
The one difference which is more difficult to reason away pertains 
to the numbers of individuals exhibiting leveling movements. In the 
New Mexico colony, although the number of individuals observed was 
not large, all appeared to level the mound at the nest entrance in the 
manner characteristic of the species. In the Texas colony the majority 
did not, but roughly 25% of the individuals leveled in exactly the 
same way as the members of the New Mexico colony. It would be 
most interesting to study colonies from other parts of the range in this 
regard. It is conceivable that this percentage may be found to reflect 
a difference in gene frequency which varies clinally somewhat as color 
pattern appears to do in this species. On the other hand, one cannot 
be certain that even this difference is genetic; it is possible that the 
movements are innate but subject to threshold factors which were 
dependent upon the differing ecology of the two areas. 
On the whole one cannot help but be much impressed by the similar- 
ity in the nesting behavior of these two widely separated colonies as 
well as the several unique features in the behavior of the species. In 
the following paragraphs some of the more significant features of the 
behavior are discussed one by one. 
( 1 ) The species is crepuscular, at least with respect to hunting 
and provisioning. Some females begin hunting 2.5-3 hours before sun- 
set, but the majority do not become active until about an hour before 
sunset. From then on until about half an hour after sunset most fe- 
males leave the nest entrance open and are actively provisioning. The 
