Pogonomyrmex rugosus, a group forager, foraged preferentially on seeds of plant species which shed large quantities of seeds a 1 time. Pogonomyrmex desertorum, an individual forager took seeds in relation to their availability but concentrated on grass seeds late in the growing season. Pogonomyrmex californicus selected seed species which allowed it to avoid contact with its congeners. During a dry year, P. rugosus exhibited little selectivity, supporting the idea that selectivity should be decreased under conditions of low food abundance. Pogonomyrmex spp. removed a significant fraction of the seed production of only 1 species, Bouteloua barbata. It is suggested that Pogonomyrmex foraging may affect the relative abundance of plant species.