Niche relationships among species of aphids feeding on fireweed

Three species of aphids in the genus Aphis and one in the genus Macrosiphum feed on fireweed in the Rocky Mountains of Colorado, U.S.A. These species differ in their time of colonization of fireweed, time of maximum number of colonies, feeding position on fireweed, relationships to tending ants, life table parameters, and other life history characteristics. Possible reasons for such differences among cooccurring aphids are discussed.