title: A new species of Caenis Stephens, 1836 (Ephemeroptera: Caenidae) from Southern Brazil.
abstract: A new species of the genus Caenis Stephens is described based on the male imago, female imago and egg stages from the state of Rio Grande do Sul, Brazil. The male imago of Caenis gaucha sp. nov. is diagnosed as follows: body length of male 2.0-2.5 mm; base of antennal flagellum not dilated; forceps apically rounded, not fused to lateral margins of styliger plate; styliger plate short with posterior margin slightly sub-triangular; ratio of foreleg 1.7-2.2 × the length of hind leg, forceps length 4.4-6.0 × the width ½ from base, and distance between the extreme lateral points of the forceps bases 1.7-1.8 × forceps length.
authors.affiliation: Laboratório de Diversidade Animal e Vegetal, Campus Heróis do Jenipapo Universidade Estadual do Piauí, CEP 64280-000, Campo Maior-PI, Brazil.; Email: lucaslima_86@hotmail.com.
authors.forename: Lucas R C
authors.initials: LR
authors.lastname: Lima
authors.affiliation: Instituto de Biodiversidad Neotropical, CONICET (National Council of Scientific Research)-Universidad Nacional de Tucumán, Tucumán, Argentina, UNASUR.; Email: carlosmolineri@gmail.com.
authors.forename: Carlos
authors.initials: C
authors.lastname: Molineri
authors.affiliation: Laboratório de Porifera, Centro de Ciências Biológicas, Departamento de Zoologia, Universidade Federal de Pernambuco, CEP 50670-420 Recife-PE, Brazil.; Email: uspinheiro@hotmail.com.
authors.forename: Ulisses
authors.initials: U
authors.lastname: Pinheiro
mesh_terms: D000825:Animal Structures / Q000033:anatomy & histology / Q000254:growth & development; D000818:Animals; D049628:Body Size; D001938:Brazil; D065133:Ephemeroptera / Q000033:anatomy & histology / Q000145:classification* / Q000254:growth & development; D005260:Female; D008297:Male; D009929:Organ Size