THE HARVESTING ANTS. 



283 





but the species are almost exclusively confined to the dry moun- 

 tainous deserts and plains, where some of them ascend to an altitude 

 of 5,000-8,000 feet. Most of them are aggregated in two groups, 

 one of which inhabits Argentina and Chile; the other the South- 

 western States and northern Mexico, and few are known to occur 

 in the long intermediate region. The subgenus Ephebomyrmex, 

 which comprises small, beardless species, with coarse, reticulate sculp- 

 ture is represented by a single form (E. schinitti ) in Hayti, another 

 (E. iKcgclii) in Brazil, and a few in Mexico, Texas and Arizona 

 (E. inibcrbii-nlits, f^iina and townsendi). Another subgenus, Janetia, 

 is represented by a single species (/. inayri ) in Colombia. Only one 

 of the species of Pogonomyrmex s. sir., the Florida harvester (P. 

 bad ins), is known to occur east of the Mississippi River. According 

 to Forel (icpiin), P. occidentalis has been taken in Hawaii. 



Little is known of the habits of 

 the South American Pogonomyrmex. 

 Berg (1890) has published a few 

 notes on P. cnnicnlaris and five other 

 species occurring in Argentina. Chile 

 and Uruguay, but no mention is made 

 of their harvesting habits. Their nests 

 seem to be insignificant, with the 

 exception of those of cunicularis, 

 which are described as surmounted 



1)V craters SO cm. in diameter erected gonomyrmex molefaciens. a small pile 



of pebbles hiding the nest entrance : 



in sandy soil. Janetia, according to natural size. (Original.) 

 Forel, does not harvest seeds, but this 



statement is open to doubt. All of the North American Pogonomyrmex 

 ( including those of the subgenus Ephebomyrmex) are unquestionably 

 harvesting ants, although none of them disdains insect food whenever 

 it can be procured. They all excavate their nests in soil fully exposed 

 to the rays of the sun and are able to endure prolonged droughts. 

 According to my observations our species may be divided into four 

 groups, as follows : 



i. P. subdcntatiis, apache, sancti-hyacinthi and desertorum, and 

 Ephebomyrmex imberbiculus, townsendi and pinia. These are small 

 species confined to the deserts of Texas, New Mexico, Arizona, Cali- 

 fornia and northern Mexico. Their colonies are always insignificant 

 and widely scattered, comprising only a few dozen individuals. Tire 

 nests are small, obscure craters, 10-20 cm. in diameter and a few centi- 

 meters high. The workers make no attempt to cut down the surround- 

 ing vegetation, which often grows on the crater immediately around 

 the entrance. 



FIG. 161. Incipient nest of Po- 



