1907.] 



Whcclcr, Fungus-growing Ants of North America. 



755 



tenfrionalis, a condition which also obtains in sandy portions of the post-oak 

 woods. 



Though structurally closely resembling the eastern species, 2\ turrifcx 

 may be readily distinguished by a number of ethological characters. Its 

 colonies are much smaller, often consisting of only two or three dozen individ- 

 uals. Nevertheless a single nest may contain as many as four or five dealated 

 females. The nesting habits are most conveniently studied in the post-oak 

 woods, where the ants prefer to live in the shade of the trees. Here the 

 red clay is overlaid with a stratum of less compact black soil two or three 

 decimeters deep. The external structure of the nest is very different from 



Fig. 24. Turret-shaped entrance to nest of Alta iTnichymynncv) turrifex in a cedar Ijrake 

 near Austin, Texas. (Photograph by Mr. A. L. Melander.) 



that of .scptcntrlonalis. The orifice is only 3-4 mm. in diameter anil in 

 typical nests, does not open on the surface of the soil but at the top of a 

 cylindrical turret or chimney about 10 mm. in diameter and from 10-40 nun. 

 high. The walls of this turret, which are made of earth particles, small 

 juniper twigs and other vegetable debris (Fig. 24) are sufficiently resistant 

 to withstand heavy showers. As the nests are often located on sloping 

 grouml the turret would seem to be an ingenious adaptation for keeinng 

 the water from entering the subterranean galleries and chambers. Occa- 



