Primocerus neutrum, Girón & Short, 2019

Giron, Jennifer C. & Short, Andrew Edward Z., 2019, Three additional new genera of acidocerine water scavenger beetles from the Guiana and Brazilian Shield regions of South America (Coleoptera, Hydrophilidae, Acidocerinae), ZooKeys 855, pp. 109-154 : 142-144

Primocerus neutrum sp. nov. Figs 11 E–H , 14D , 15A , 16C

Type material.

Holotype (♂): "VENEZUELA: Bolívar / 6°2'10.5"N, 61°23'57.8"W; 630 m/ along La Escalera; rocky stream/ 31.vii.2008; leg. A. Short, M. García, 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: Bolívar: 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 × 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 ).

Figures

Figure 11. Habitus of Primocerus spp.: A-D Primocerus cuspidis: A dorsal view B lateral view C ventral view D head, dorsal view. E-H Primocerus neutrum: E dorsal view F lateral view G ventral view H head, dorsal view. Scale bars: 1 mm.

Figure 14. Thorax, abdomen and aedeagus of Primocerus spp.: A-D Primocerus neutrum: A ventral view of mesoventrite (white arrow pointing transverse ridge) B posterior view of metafurca C fifth abdominal ventrite D aedeagus. E-L aedeagus: E, F Primocerus maipure: E dorsal view F lateral view. G, H Primocerus pijiguaense: G dorsal view H lateral view I Primocerus gigas J Primocerus petilus K Primocerus striatolatus L Primocerus cuspidis. Scale bars: 0.25 mm.

Figure 15. Distribution of Primocerus spp.

Figure 16. Habitat of Primocerus spp. A habitat and type locality for P. cuspidis, Venezuela, Tobogan de la Selva, collecting event AS- 08 - 080 b B habitat and type locality for P. pijiguaense, Venezuela, Los Pijiguaos, collecting event AS- 07 - 015 C habitat and type locality for P. neutrum, Venezuela, along La Escalera, collecting event AS- 08 - 058 D habitat and type locality for P. petilus, Brazil, Vale do Paraiso, collecting event BR 18 - 0203 - 01 G.