Hagen's small minnow mayfly (Ephemeroptera : Baetidae) in North America

The study of newly acquired larvae and adults of Diphetor devinctus associa ted by rearing in California showed larvae to be indistinguishable from tho se of D. hageni. This, and the further observation from extensive materials that male genitalia differences previously accorded the two species do not hold up but are highly subject to individual and population variability, a re the basis for placement of D. devinctus as a junior subjective synonym o f D. hageni, n. syn. The complex nomenclatural history of the North America n species and monobasic genus as well as characterization are reviewed, and distribution is documented.