ABSTRACT The subfamily Veliinae (Heteroptera: Gerromorpha: Veliidae) includes ten genera worldwide, seven of which are endemic to the American continent. Here, we provide a revision of Platyvelia Polhemus and Polhemus, 1993, which is distributed from the United States to northern Argentina, and included nine valid species prior to this study. Six species are redescribed, the synonymies of P. egregia (Drake and Harris, 1935) and P. verdica (Drake, 1951) with P. brachialis (Stål, 1860) are proposed, a lectotype is designated for P. annulipes, and two species groups are erected based on male characters: the P. annulipes group and the P. brachialis group. Keys to the species groups and species within each group, photos, and distribution maps are also included.

Uma lista das espécies de Heteroptera aquáticos e semi-aquáticos para a região sul do Estado de Mato Grosso do Sul é apresentada. O material foi coletado entre 2008 e 2009. As amostras foram obtidas a partir de 10 córregos (Água Boa, Cerro Verde, Cumprida, Ponte, Doradão, Guaçú, Guaporites, Nhú-Verá, Perobão e Santa Maria), um rio (rio Iguatemi) e nove lagoas (Bacal, Balan, da Ponte, Cinco, Macrófitas, Bugão, Sítio, Cascalho, Oxbow). Um total de 63 espécies de heterópteros aquáticos e semi-aquáticos foram registrados, das quais 32 são novos registros.

A list of aquatic and semi-aquatic Heteroptera species from the southern region of Mato Grosso do Sul State is presented. The material was collected between 2008 and 2009. Samples were obtained from 10 streams (Água Boa, Cerro Verde, Cumprida, Ponte, Doradão, Guaçú, Guaporites, Nhu-Verá, Perobão and Santa Maria), one river (Iguatemi River) and nine ponds (Bacal, Balan, Ponte, Cinco, Macrófitas, Bugão, Sítio, Cascalho, and Oxbow). A total of 63 aquatic and semi-aquatic species of Heteroptera were recorded, of which 32 are new records.