ABSTRACT Lelegeis Champion, 1886 occurs only in the Neotropical region and comprises four species: L. aeneipennis Champion, 1886 from Mexico; L. apicalis Laporte & Brullé, 1831 from Cuba; L. hispaniolae Triplehorn, 1962 from Haiti and the Dominican Republic; and L. nigrifrons (Chevrolat, 1878) occurring in Brazil, Mexico, Panama, Peru and Venezuela. Here, Lelegeis pytanga sp. nov. is described based on specimens collected in the Atlantic Forest of Brazil, and the first detailed description of the sclerites of the male and female terminalia of Lelegeis is produced. The new species can be easily distinguished from the other Lelegeis by its dull reddish brown to reddish orange elytral coloration, while the remaining body surface is dull black. The morphology of Lelegeis and its generic boundaries within Diaperinae are discussed.