The Neotropical species of the water scavenger beetle genus Notionotus Spangler, 1972 are revised using an integrative taxonomic approach combining morphology with DNA sequence data from two genes. Support exists for four putative species groups into which 18 species are placed, including twelve that are described here as new: N. bicolorsp. nov. (Suriname), N. bifidussp. nov. (Venezuela), N. brunbadiussp. nov. (Brazil), N. garciaesp. nov. (Brazil), N. giraldoisp. nov. (Brazil), N. insignitussp. nov. (Venezuela), N. jumasp. nov. (Brazil), N. parvussp. nov. (Suriname), N. patamonasp. nov. (Guyana), N. peruensissp. nov. (Peru), N. retusussp. nov. (Guyana), and N. vatiussp. nov. (Brazil). Four new synonymies are created: N. shorti Queney syn. nov. is found to be conspecific with N. dilucidus Queney; N. edibethae García syn. nov., N. nucleus Perkins syn. nov., and N. perijanus García syn. nov. are found to be conspecific with N. tricarinatus Perkins. New records are provided for all previously described species except N. mexicanus Perkins. Within the Neotropical region, the range of the genus is greatly expanded and now known from as far south as Bolivia and the Brazilian state of Mato Grosso do Sul. While a few species are found in hygropetric habitats, most are associated with the margins of forested streams. Genitalia and habitus images are provided for nearly all species, as well as a key to the four species groups.

A list of species of Hydrophilidae from Quindío Department, Colombia is presented. This list is based on recently collected specimens, a survey of data from the literature, and specimens deposited in the Colección de Insectos de la Universidad del Quindío (CIUQ). Twenty-three species, including 16 new records from Colombia, are listed. Information about biology of each species and a checklist of the overall Colombian species are given.

Two new species of Hemiosus (Coleoptera: Hydrophilidae) from the central cordillera of the Colombian Andes are described. Hemiosus molanoi González-Rodríguez & García-Hernández sp. nov. and H. quindiensis González-Rodríguez & Clarkson sp. nov. are described based in 56 adult specimens collected in river-associated sandy puddles (26 specimens of H. molanoi sp. nov.) and temporary puddles near crops (26 specimens of H. quindiensis sp. nov.). Both species are identified mainly by characteristics of the aedeagus: Hemiosus molanoi sp. nov. has subtriangular parameres, median lobe shorter than parameres and longer than appendices which are acuminate and phallobase shorter than parameres, strongly asymmetrical in basal two-fifths; H. quindiensis sp. nov. has parameres gradually tapering towards rounded apices, median lobe shorter than parameres and longer than appendices which are acuminate and phallobase shorter than parameres, strongly asymmetrical in basal half. Dorsal coloration pattern, overall shape of the meso- and metaventral process and abdominal ventrites are also informative to distinguish the new species from remaining described Hemiosus. Diagnoses, illustrations and habitat characteristics are provided.