Three additional new genera of acidocerine water scavenger beetles from the Guiana and Brazilian Shield regions of South America (Coleoptera, Hydrophilidae, Acidocerinae) Author Giron, Jennifer C. Department of Ecology & Evolutionary Biology, and Division of Entomology, Biodiversity Institute, University of Kansas, Lawrence, KS 66045, USA https://orcid.org/0000-0002-0851-6883 entiminae@gmail.com Author Short, Andrew Edward Z. Department of Ecology & Evolutionary Biology, and Division of Entomology, Biodiversity Institute, University of Kansas, Lawrence, KS 66045, USA text ZooKeys 2019 855 109 154 http://dx.doi.org/10.3897/zookeys.855.33013 journal article http://dx.doi.org/10.3897/zookeys.855.33013 1313-2970-855-109 F5A7AE8B38834CFD859FB2F3F9A079C0 F460A02DFFD1FB56FFF2FF94FFB2FFAC 3251190 Primocerus neutrum sp. nov. Figs 11 E-H , 14D , 15A , 16C Type material. Holotype (♂): "VENEZUELA: Bolivar / 6°2'10.5"N , 61°23'57.8"W ; 630 m/ along La Escalera; rocky stream/ 31.vii.2008; leg. A. Short, M. Garcia , L. Joly/ AS-08-058" (MIZA). Paratypes (20): GUYANA: Region 8 : " 4°43'49"N , 59°1'35"W ; 300 m/ Iwokrama Forest, Pakatau hills/ flight intercept trap; 26-29.v.2001/ leg. R. Brooks & Z. Falin; GUY1BF01 063" (SEMC, 1); " 5°0.730'N , 59°38.965'W ; 585 m/ Upper Potaro camp I, c. 7 km NW Chenapau, Ridge Trail/ 11.iii.2014; leg. Short, Baca, Salisbury; GY14-0311-02A" (CBDG, SEMC, 11); " 5°18.261'N , 59°50.257'W ; 687 m/ Ayanganna Airstrip, trail from airstrip to Ayanganna/ forest detrital pools; 17.iii.2014/ leg. A. Short; GY14-0317-01A" (SEMC, 1); same except "18.iii.2014, GY14-0318-01B" (SEMC, 1); same except "seepage area over rocks in forest flowing into stream, GY14-0318-01C" (SEMC, 1). SURINAME: Sipaliwini District : " 3°53.942'N , 56°10.849'W ; 733 m/ CSNR: Tafelberg Summit, nr. Caiman Creek Camp/ pools in forest; 19.viii.2013/ leg. Short & Bloom; SR13-0819-05B" (SEMC, DNA voucher specimen SLE 1085). VENEZUELA: Bolivar : Same data as holotype (MIZA, SEMC, 8, including DNA voucher SLE 529). Differential diagnosis. Primocerus neutrum can be regarded as very plain in appearance, lacking remarkable features. It can be distinguished among similarly sized species with shallowly punctured elytra by its dark brown coloration and simple transverse ridge on the posterior elevation of the metaventrite. Description. Body length 2.6-3.5 mm, width 1.4-1.9 mm. Body elongate oval, moderately convex (Fig. 11F ). General coloration brown. Elytra with ground punctures very shallowly marked. Posterior elevation of mesoventrite with simple curved transverse ridge. Metafemora with hydrofuge pubescence covering nearly basal 4/5 of anterior surface. Apex of fifth abdominal ventrite slightly emarginate. Aedeagus (Fig. 14D ) with basal piece nearly 1.25-1.35 x longer than parameres; parameres slightly longer than median lobe, truncate to rounded and obliquely directed at apex; apex of median lobe somewhat "pinched" and narrowly pointed. Etymology. Named with the Latin word neutrum meaning neutral, in reference to the comparatively unremarkable appearance of the species. Distribution. Primocerus neutrum has been collected at the locality known as La Escalera in the Venezuelan Amazon, the Upper Potaro region and the Iwokrama Forest in Guyana, and the Tafelberg summit in Suriname. Specimens have been collected at elevations of 300-733 m (Fig. 15A ). Remarks . This species has been collected in detrital pools in densely forested areas, typically associated with streams (Fig. 16C ).