Nanelmis Barr, a New Genus of Diminutive Riffle Beetle (Coleoptera: Dryopoidea: Elmidae: Elminae) from South America with Two New Species

Nanelmis Barr, new genus with two new species, Nanelmis aguaje Barr, new species from Peru and Nanelmis longicruris Barr, new species from French Guiana, are diagnosed, described, and illustrated, as is the larva of N. aguaje. Adult specimens of both species are tiny, less than 2 mm long. Despite the fact that a fairly large series of N. aguaje was collected, all are female. Nanelmis longicruris is described from a single male which has modifications that are likely due to sexual dimorphism. Each species is known from a single locality, both of which are described in detail.