Diura washingtoniana (Hanson, 1940) is reinstated from synonymy with D. nanseni (Kempny, 1900). The adult male and female are more completely described and the larva and egg of this species are described for the first time. Diagnostic features for D. washingtoniana are presented and this species is compared to the following congeners: D. nanseni, D. bicaudata (Linnaeus, 1758) and D. knowltoni (Frison, 1937) using line illustrations, scanning electron photomicrographs, and color photographs.