I (,l> 



.IMS. 



other during- March and April and again during late summer or early 

 autumn (September). The summer nests are built in open, sunny 

 plare^ where food i> abundant and the conditions most favorable to 

 rearing the brood, whereas the winter nests are built under stumps and 



FIG. 108. Nest of Pogonomynne.r occidentalis at Las Vegas, New Mexico; showing 

 the basal entrance on the southeastern side. (Original.) 



rocks usually in protected spots in the woods, and are used as hiber- 

 nacula, or, very rarely, for protection from excessive heat during the 

 summer. 



The migration of ants from one nest to another is determined upon 

 and initiated by a few workers which are either more sensitive to 

 adverse conditions or of a more alert and venturesome disposition than 

 the majority of their fellows. These workers, after selecting a site, 

 begin to deport their brood, queens, males, fellow workers and even 

 their myrmecophiles. The deported workers are at first too strongly 

 attached to their old quarters to remain in the new ones and therefore 

 keep returning and carrying back the brood. The enterprising workers, 

 however, obstinately persist in their endeavors to move the colony till 

 their intentions are grasped and become contagious. The indecision or 

 indifference of many of the workers may last for days or even for 

 weeks, during all which time files of ants move back and forth between 

 .the two nests carrying their larvae and pupae in both directions. But 



