254 ENTOMOLOGICAL NEWS. [June, ’12 
A glance at Plates XV and XVI will show that there is some 
variation in the nests as regards the number of cells, and the 
length of the galleries. Some contained as many as eight cells, 
but in all cases the tunnel starts vertically and may lead to 
cells at one or more points. As with O. annulatus their holes 
are very neat and smooth, often somewhat widened where 
branching begins. The diameter of the entrance to the chambers 
is at this point about one-half that of the enlargement. Some 
of the holes were frequented by males which, entering them 
now and then, basked inside the entrance. 
A brief comparison of the nest habits of O. annulatus and 
geminus may be of interest. 
Ist. Annulatus and geminus occur in the same locality but 
differ somewhat widely in habits, for: 
2nd. While annulatus constructs a tube over its nest, gemi- 
nus does not. 
3rd. Annulatus, in disposing of the unused earthen pellets 
extracted from its burrow, deposits them at a distance of sev- 
eral feet from its nest; geminus, on the other hand, drops at 
least a good proportion of the pellets only an inch or two from 
its burrow. 
4th. Annulatus provisions its nest with the larvae of Loro- 
stege sticticalis (Pyralidina), geminus with the larvae of Pho- 
lisora catullus ? (Hesperidae), although the larvae of sticti- 
calis was common in the locality frequented by geminus. 
What advantage the clay tube constructed by O. annulatus 
has over the plain unadorned shaft of O. geminus is difficult 
to explain. Apparently and logically the conditions that would 
favor the tubed nest would appear to be harmful to a tubeless 
nest, both situated in similar localities, or vice versa. Would 
the tube serve as a protection against dust and floods, or to 
lessen the often intense heat of the plains within the nest? A 
more plausible explanation for the tube-building habits of 
annulatus would be that the clay device protects the nest from 
the attacks of insect enemies. Certainly the tube nests are less 
easily discerned than the plain holes with a small heap of pel- 
lets in the immediate vicinity. A Mutillid, for example (which 
