Three species of Diuraphis in addition to the Russian wheat aphid, Diuraphis noxia (Mordvilko), occur in western Colorado. Diuraphis (Holcaphis) tritici (Gillette), the western wheat aphid, and Diuraphis nodulus (Richards) were collected near Meeker (Rio Blanco County) in 1990. Both species were found feeding in seed production fields of mountain brome, Bromus marginatus, and have required chemical control at times to avert economic damage. Diuraphis (H.) frequens Walker was found in 2 localities in 1990. It was found in all but 1 growing season since that time in the West Elk Wilderness (Gunnison County), feeding on blue wild rye, Elymus glaucus. Males and oviparae of all 3 species were collected in 1991. Eggs of D. (H.) tritici and D. nodulus were collected in the spring and again in the fall of 1992. Two species of parasitic Hymenoptera, and 2 species of hyperparasites were collected from D. (H.) tritici and D. nodulus during the study. Several predatory beetles, flies, true bugs, and green lacewings were collected from all of the Diuraphis species.