During the summer of 1974 in the Imperial and Palo Verde Valleys of southern California, population densities of arthropod predators andHetiothisspp. were studied after insecticide treatments for the pink bollworm.Geocorisspp.,Orius tristicolor(White) and spiders were the most numerous arthropod predators.Chrysopa carneaStephens andCollops marginellusLeConte were least affected by increased insecticide usage.The mean density of arthropod predators was significantly reduced while the mean density ofHeliothisspp. was significantly increased by increased insecticide usage.