Tricorythodes molinerii sp. n. is described and illustrated based on nymphs from southeastern Brazil. The new species can be distinguished from other species of Tricorythodes Ulmer by the following characters: 1) genal projection present; 2) maxillary palp bi-segmented, with short apical seta; 3) pronotum with well developed anterolateral projection; 4) dorsum of fore femora with a transverse row of setae; 5) tarsal claws without marginal denticles and with one submarginal denticle on each side; 6) operculate gills triangular, shaded with black, and with whitish mark in subbasal zone; and 7) very large size.
Taxonomy; aquatic insect; Tricorythodes molinerii; Neotropics; Ephemerelloidea
