The genus Androprosopa Mik (Diptera: Thaumaleidae) is redefined and expanded to include 51 species. Adult, pupa, and final-instar larva of the eastern North American species of Androprosopa americana (Bezzi) comb. n., A. thornburghae (Vaillant) comb. n., A. vaillantiana sp. n., and Thaumalea verralli Edwards (new Nearctic record) are described and illustrated. New records of Trichothaumalea elakalensis Sinclair also are provided. Keys to adult males, pupae, and larvae for all five eastern Nearctic species are included.