RESUMO
We examined material from two poorly documented areas in Brazil concerning the mayfly genus Thraulodes: Minas Gerais, the largest state in Southeastern Brazil, but also the least studied regarding mayflies; and Tocantins, located in the North-Central area of the country. As a consequence of these efforts, we describe a new species from Minas Gerais based on imagos and nymphs, as well as the nymphs of Thraulodes solstitium Orlando, Salles, Boldrini & Krolow, 2021. Thraulodes viola sp. nov. is characterized by the femora translucid with brown maculae and blackish stripe in distal half, and a light brown maculae in proximal half; abdominal terga II-VI translucent white with transversal reddish mark on posterior margins, one antero-lateral reddish dot, one antero-sublateral blackish spot, and one postero-submedian brown spot; penis lobes sinuous sideways, with lateral pouch present and very developed, and apico-lateral area with an ear-like projection; nymph with galea-lacinia dark brown, 14-16 medium-sized pectinate setae in subapical-ventral row. The nymph of T. solstitium nymph is characterized by the galea-lacinia dark brown, 11 medium-sized pectinate setae in a subapical-ventral row.