A new species of Denopelopia from Brazil is described based on adult male and pupa. The male of the new species can be distinguished from all other species of the genus by the genitalia and fore-tibial spur morphology. The pupa is very similar to those of Denopelopia atria, but it can be distinguished by the absence of distinct constrictions in the respiratory atrium of the thoracic horn. Generic diagnosis to male and pupa of Denopelopia is emended and keys to male and pupae of known species are provided.
Keywords: Amazonian; Neotropical Region; Pentaneurini; Tanypodinae; aquatic Insects; taxonomy.