Abstract The study of ca. 280 specimens of Cercyon Leach, 1817 (Hydrophilidae: Sphaeridiinae: Megasternini) deposited in the Coleção Entomológica Pe. J.S. Moure, Universidade Federal do Paraná, Brazil, revealed a new species from Atlantic Rain Forest biome in Paraná State (Southern Brazil) and new records. Cercyon (Cercyon) curi sp. nov. is herein described and illustrated, belonging to the Neotropical C. variegatus species group. Cercyon (Cercyon) nigriceps (Marsham, 1802) is recorded for the first time in Paraná State, and Cercyon (Cercyon) inquinatus Wollaston, 1854 from Amazonas State (Northern Region); these records extend the distributional range of both species in Brazil. Cercyon (Cercyon) praetextatus (Say, 1825) is recorded for the first time from Brazil based on specimens collected in Paraná. Those three species were previously recorded as introduced in South America.

Abstract As an add-on to the work of Clarkson et al. (2016), new distributional data on species of Helobata Bergroth, 1888 (Hydrophilidae: Acidocerinae) from Brazil is provided. Helobata amazonensis Clarkson, Santos & Ferreira-Jr., 2016, is recorded for the first time for Roraima State and its female is recorded for the first time. Helobata quatipuru Fernández & Bachmann, 1987 and H. larvalis (Horn, 1873) are recorded for the first time for Minas Gerais, Cerrado Biome area. The genus is recorded for the first time for Goiás State. Additions and modifications in the previously published key to Brazilian species are provided.

A new species of Helochares Mulsant, 1844 (Hydrophilidae: Acidocerinae) from Brazil is described and illustrated. Helochares (s. str.) atlanticus sp. nov. is distinct mainly by characteristics of the aedeagus whose phalobase is short, narrowed on basal third; parameres are thick, constricted on apical quarter, with small tooth-like projection on outer margin near apex; dorsal lobe longer than ventral lobe, shorter than parameres, very wide at base, abruptly narrowing toward apex until about half of its length where it dilates and divides into two long and narrow projections apart from each other at base, but turned inward at apex; ventral lobe acuminate and symmetrical. The rounded emargination on anteromedial margin of labrum bearing small tooth-like projections and the convex and slightly elevated mesoventral process, without high-elevated carina, also helps in identifying the species. Specimens of the new species were collected in the mountain region of the state of Rio de Janeiro (municipality of Teresópolis) and in the north coast of the state of São Paulo (municipality of Ubatuba), both localities in Southeastern Brazil. Helochares (s. str.) oculatus Sharp, 1882 and Helochares (Sindolus) femoratus (Brullé, 1841) are recorded for the first time from the state of Rio de Janeiro.