Macrostemum is the second largest genus of Macronematinae with about 104 described species distributed in the Neotropical (18), Afrotropical (20), Australasian (7), Palearctic (2), Nearctic (3) and Oriental (54) regions. Despite its great diversity, knowledge about its immature stages is scarce: worldwide, only 7 species (6.7%) have larvae and/or pupae described. From the Neotropics, only one species, Macrostemum ulmeri (Banks, 1913), has described larvae and pupae. The objectives of this study are to describe and illustrate a new species, Macrostemum araca sp. nov., based on adult males and females from Serra do Aracá, Amazonas, Brazil, and the larvae and pupae of M. brasiliense (Fischer, 1970) from an Atlantic Forest fragment in São Paulo state using the metamorphotype method. In addition, this species is recorded for the first time for Minas Gerais state.
Aquatic insect, larva, pupa, taxonomy, Neotropical, Serra do Aracá, Atlantic Forest.