THERE ARE PRESENTLY SEVEN SPECIES OF Hippelates eye gnats which are adapted to varying climatic situations in California and southwestern United States. One species, Hippelates collusor (Townsend), is of wide-spread concern because it has become well adapted to year-around breeding in the hot interior agricultural areas of the Southwest, where field cultivation is practiced. Hippelates pusio Loew, also an agricultural breeder, is more restricted to the cooler climatic conditions on the coast. Two species, Hippelates robertsoni Sabrosky, and a recent invader from Mexico, H. impressus Becker, inhabit the mountains or lowlands in the spring. They cannot tolerate the extreme heat of summer in the lowlands of this region. Species that are of little annoyance or whose density is extremely low are H. microcentrus Coquillett, H. dorsalis Loew and H. hermsi Sabrosky.