254 ENTOMOLOGICAL NEWS. [June, 'l2 



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 Lo.ro- 

 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 gcminus. 



What advantage the clay tube constructed by 0. 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 



