Chasmogenus cuspifer, Smith & Short, 2020

Smith, Rachel R. & Short, Andrew Edward Z., 2020, Review of the genus Chasmogenus Sharp, 1882 of northeastern South America with an emphasis on Venezuela, Suriname, and Guyana (Coleoptera, Hydrophilidae, Acidocerinae), ZooKeys 934, pp. 25-79 : 25

Chasmogenus cuspifer sp. nov. Figures 7B , 8D , 12D , 17 , 19A-C

Type material.

Holotype (male): "Venezuela: Zulia State/ 9°50.490'N, 72°49.310'W, 270 m/ Perija N.P. Tukuko: Río Manantial/ 29.i.2009; Short, García, Camacho/VZ09-0129-01A: gravel margin"/ "[barcode]/SEMC0857741/ KUNHM-ENT", "HOLOTYPE/ CHASMOGENUS/ cuspifer sp. n./ des. Smith & Short" (MIZA). Paratypes (19): Venezuela: Aragua State: Henri Pittier National Park, Rio La Trilla, 10.37319N, 67.74250W, 295 m, 4.i.2009, leg. Short, Miller, Camacho and García, pools, VZ09-0104-01A (1 ex., SEMC, DNA Voucher SLE532). Zulia State: Perija National Park, Tukuko: Rio Manantial, 9°50.490'N, 72°49.310'W, 270 m, 29.i.2009, leg. Short, García and Camacho, gravel margin, VZ09-0129-01A (11 exs., MIZA, SEMC, including DNA Voucher SLE533); same data as previous except: 16.vii.2008, leg. A. Short, margins and pools, AS-08-027 (2 exs., SEMC); same data as previous except: 22.ix.2007, rock pools/margin, leg. A. E. Z. Short, AS-07-020b (3 exs., SEMC); Perija National Park Toromo, 10°03.058'N, 72°42.974'W, 435 m, 31.xii.2005, leg. A. E. Z. Short, small stream and seep, AS-06-001 (1 ex., SEMC), same data as previous except: 28.i.2009, leg. A. Short, detrital pool, VZ09-0128-01A (1 ex., SEMC).

Differential diagnosis.

See differential diagnosis for Chasmogenus bariorum .

Description.

Size and color. Total body length 3.0-3.2 mm. Body form elongate oval with slightly curved lateral margins. Dorsum of head very dark brown to black, anterior margin of labrum slightly paler in color (Fig. 8D ). Pronotum dark brown, distinctly paler at lateral margins; elytra dark brown. Venter dark red-brown mesally, dark brown marginally. Head. Ground punctation on head fine. Clypeus with anteromedial emargination, which exposes a small angulate gap between clypeus and labrum (Fig. 8D ). Mentum very weakly depressed in anterior half with widely rounded anteromedial notch followed by rounded elevated ridge just posterior of the notch. Maxillary palps long, longer than width of head immediately posterior to eyes. Thorax. Ground punctation of pronotum fine. Prosternum tectiform. Mesoventrite with strong elevation forming an acute tooth posteromedially (Fig. 7B ). Metafemora densely pubescent in basal four-fifths. Aedeagus. Aedeagus (Fig. 12D ) with median lobe subtriangular in shape, widest at base and gradually tapering along entire length; apex acute, which extends to the same level as the inner cusp of the parameres. Sclerite of the median lobe not expanded. Gonopore situated slightly less than one gonopore width below the apex of the median lobe. Parameres symmetrical, with outer margins slightly curved along entire length, appearing weakly convex; apex bifid, with outer lobe slightly more elevated than inner lobe; inner lobe much narrower than outer lobe. Basal piece very long, distinctly longer than the length of the parameres.

Etymology.

The species name is derived from the Latin cuspis, meaning “pointed”, after the toothed mesoventral carina.

Distribution.

This species is known from stream habitats in the Perijá and the Coastal Mountains of Venezuela (Fig. 17 ).

Biology.

All specimens were collected in the margins of forested stream habitats, typically with gravel margins (Fig. 19C ).

Figures

Figure 7. Lateral view of mesoventrite. A C. bariorum B C. cuspifer. Scale bar: 0.10 mm.

Figure 8. Dorsal view of heads of Chasmogenus spp. A C. castaneus B C. australis C C. bariorum D C. cuspifer E C. flavomarginatus F C. lineatus.

Figure 12. Aedeagi (dorsal view) of Chasmogenus spp. A C. castaneus B C. flavomarginatus C C. flavomarginatus D C. cuspifer E-I C. lineatus. Scale bar: 0.25 mm.

Figure 17. Distribution of Chasmogenus spp.

Figure 19. Habitat of Chasmogenus spp in the Andean region of Venezuela. A, B Type locality and habitat for C. bariorum, C. cuspifer, and C. castaneus, near El Tukuko, Rio Manantial collecting event VZ 09 - 0129 - 01 A) C habitat for C. bariorum and C. cuspifer, Henri Pittier National Park, Rio Cumboto (collecting event VZ 09 - 0104 - 02 B) D type locality and habitat for C. flavomarginatus, ca. 13 km NW of Baranitas (collecting event VZ 12 - 0124 - 02 B) E habitat for C. bariorum and C. lineatus, between San Juan and Dos Caminos, Rio San Antonio (collecting event VZ 09 - 0108 - 02 A) F habitat for C. bariorum and C. lineatus, near Arenales, Rio Salado (collecting event VZ 09 - 0122 - 01 X).