Uma nova espécie de Fissimentum Cranston & Nolte, 1996 do estado de São Paulo, Brasil (Diptera: Chironomidae, Chironominae)

Fissimentum mendesi n. sp. is described and figured on the basis of males collected in light traps in two localities in the state of Sao Paulo, Brazil. The new species is apparently closely related to F. desiccatum Cranston & Nolte, 1996 and F. guairense Pinho & Froehlich, 2011 by having a posterior projection of tergite IX, but can easily be distinguished from its congeners on the combination of a short, stout, evenly curved superior volsella and an antennal ratio of about 1.5. A revised key to the males of the genus is provided.