Abstract
The Chilean water penny genus Tychepsephus Waterhouse, 1876 is revised, with descriptions and photographic illustrations of life stages including two larval morphotypes, the pupa of one morphotype, and adults of two species. The pupa of Tychepsephus has not been reported previously. Tychepsephuscekalovicisp. nov. is described, and Ectopria (Chilectopria) grandis Pic, 1947, syn. nov. is proposed as a new synonym of Tychepsephusfelix Waterhouse, 1876, which is redescribed. Taxonomic treatment of the adults of both species includes images of the habitus of males and females, morphological variation, and male and female genitalia. Males and females are sexually dimorphic. Information on the habitat of Tychepsephus is provided and illustrated with photographs, and the known geographic distribution of the two species is mapped. The occurrence of Tychepsephus in Argentina is reported; therefore, the genus no longer can be considered endemic to Chile. The taxonomic status and geographic distribution in South America of other species of Psephenidae, particularly members of the subfamily Eubriinae, is reviewed.