1934 ] 
Ants of the Snake River Plains 
221 
AN ANNOTATED LIST OF THE ANTS OF THE 
SNAKE RIVER PLAINS, IDAHO 
(HYMENOPTERA :FORMICIDAE) 
By A. C. Cole, Jr. 
Twin Falls, Idaho 
The ants of the Snake River Plains region, while compris- 
ing relatively few forms in comparison with other areas, 
are, however abundant in so far as the number of colonies 
is concerned. Floristically, the region is divided into (1) 
the vast semidesert plains of sagebrush, rabbitbrush, grease- 
wood, shadscale and bromegrass; (2) the tall perennial 
grass upland habitats, in which grow the Agropyrons and 
Stipas and subalpine meadow vegetation; and (3) the moun- 
tainous and hilly areas, chiefly inhabited by western yellow 
pine, with juniper and alder at slightly lower elevations. 
1. Pogonomyrmex occidentalis Cresson 1 
This is the dominant and most abundant ant of the semi- 
desert areas. It usually builds pebble mounds with cleared 
surrounding area. Winged forms appear from late June to 
late July. Food consists of seeds of many plants although 
chiefly those of Bromus tectorum L. (Downy Bromegrass) 
when present. Crater nests of Dorymyrmex pyramicus are 
occasionally on the mound faces and in the denuded areas. 
2. Pheidole calif ornica Mayr. 
This ant is abundant in sagebrush areas of the Snake 
River Canyon but decreases in number with northward pro- 
gression, being only occasional in the tall grass meadows. 
It nests beneath rocks, usually on hillslopes. Colonies are 
rather populous. Soldiers are present, in proportion to 
workers about one to ten. Food consists chiefly of small 
seeds and some insects. Winged forms appear in August. 
determinations and checkings by Dr. M. R. Smith. 
