Primocerus petilus, 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 : 144

Primocerus petilus sp. nov. Figs 13 A–C , 14J , 15B , 16D

Type material.

Holotype (♂): "BRAZIL: Pará: Alenquer/ 1.49292S, 54.51566W; 150 m/ Vale do Paraíso, ca. 55 km N. of Alenquer/ tiny wet rock/seepage on trail; 3.ii.2018/ leg. A. Short; BR18-0203-01G" (INPA, DNA voucher specimen SLE 1498).

Differential diagnosis.

Primocerus petilus can be recognized by the presence of sharply impressed elytral punctures, with serial punctures well differentiated (larger and deeper than remainder punctures), longitudinally aligned to form elytral striae. It is similar to P. semipubescens , from which it can be differentiated by the hydrofuge pubescence of the metafemora covering basal 3/4 of the anterior surface (covering less than basal half in P. semipubescens ). It is also very similar to P. striatolatus , from which it can be differentiated by the undefined elytral striae IX and X along the basal fourth of the elytra (Fig. 13B ; elytral striae IX and X clearly impressed along their entire length in P. striatolatus , Fig. 13E ).

Description.

Body length 3.4 mm, width 1.6 mm. Body elongate oval, moderately convex (Fig. 12A, B ). General coloration dark brown. Elytra with ground punctures sharply marked, and well-defined rows of serial punctures (forming elytral striae); elytral striae very slightly impressed along posterior half of elytra. Posterior elevation of mesoventrite with simple, curved transverse ridge. Metafemora with hydrofuge pubescence covering basal 4/5 of anterior surface. Apex of fifth abdominal ventrite rounded. Aedeagus (Fig. 14J ) with basal piece nearly 1.3 × longer than parameres; parameres nearly as long as median lobe (median lobe inserted further into basal piece, thus appearing shorter than parameres); apex of parameres narrowly rounded; apex of median lobe widely rounded.

Etymology.

Named with the Latin word petilus meaning slender, in reference to the relative slenderness of the body in this species.

Distribution.

Primocerus petilus has only been collected at one locality in the north of Brazil, at an elevation of 150 m (Fig. 15B ).

Remarks.

The single known specimen is missing the maxillary palps. It was collected on a temporary wet spot on an exposed forested rock outcrop. The rock was wet when the specimen was collected due to recent rains but was dry by the following day (Fig. 16D ).

Figures

Figure 12. Habitus of Primocerus spp.: A-D Primocerus maipure: A dorsal view B lateral view C ventral view D head, dorsal view. E-H Primocerus pijiguaense: E dorsal view F lateral view G ventral view H head, dorsal view. Scale bars: 1 mm.

Figure 13. Habitus of Primocerus spp.: A-C Primocerus petilus: A dorsal view B lateral view C ventral view. D-F Primocerus striatolatus: D dorsal view E lateral view F ventral view. G-I Primocerus semipubescens: G dorsal view H lateral view I ventral 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.