The phenomena of aestivation and overwintering of ants present a most interesting study. The similarities between the two as well as their many differences offer excellent comparisons. Little work has actually been accomplished with ants in this field in spite of the studies of arthropod hibernation instigated by Holmquist (I) and others. The purpose of this paper is to present some of the more important physical and biotic factors involved in the aestivation and overwintering periods of the Occident ant. Pogonomyrmex occidentalis Cresson, in a portion of the Northern Desert Shrub region, near Twin Falls, Idaho.