Chasmogenus berbicensis, 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 berbicensis sp. nov. Figures 9C , 14D , 17 , 22A

Chasmogenus sp. B Short, Salisbury, & La Cruz 2018: 193.

Type material.

Holotype (male): "Guyana: Region 6/ 4°08.809'N, 58°14.232'W, 108/ Upper Berbice, Basecamp 1/ margin of berbice river/ leg. Short, Salisbury, La Cruz/ 22.ix.2014; GY14-0922-02A"/ "[barcode] SEMC1357824/ KUNHM-ENT", "HOLOTYPE/ CHASMOGENUS/ berbicensis sp. n./ des. Smith & Short" (CBDG). Paratypes (6): Guyana: Region 6: same data as holotype (3 exs., SEMC including DNA Voucher SLE1864); Upper Berbice Basecamp 1m 4°09.289'N, 58°10.717'W, 96 m, 24.ix.2014, leg. Short, Salisbury, and La Cruz, margins of basecamp creek, GY14-0924-01A (2 exs., SEMC); same data as previous except, 21.ix.2014, leg. Short Salisbury and La Cruz, muddy detrital pools in drying creek bed near camp, GY14-0921-02A (1 ex., SEMC).

Differential diagnosis.

See differential diagnosis for C. amplius .

Description.

Size and color. Total body length 4.5-4.9 mm. Body form elongate oval with slightly curved lateral margins. Dorsum of head multi-colored, frons dark brown, clypeus dark orange-brown, labrum pale yellow-orange (Fig. 9C ). Pronotum red-orange, elytra pale orange-brown with serial dark brown spots. Head. Ground punctation on head fine. Clypeus with anteroposterior emargination that exposes a wide trapezoidal shaped gap between clypeus and labrum (Fig. 9C ). Mentum moderately depressed in anterior half with subtriangular anteromedial notch. Maxillary palps long, longer than width of head immediately posterior to eyes. Thorax. Ground punctation on pronotum fine. Prosternum mildly tectiform. Mesoventrite with weak elevation forming a posteromedial longitudinal carina. Metafemora densely pubescent in basal nine-tenths. Aedeagus. Aedeagus (Fig. 14D ) with median lobe widest at base, and very slightly tapering until the apical quarter, then narrowing abruptly to form an acute triangular apex which is even with or appears very slightly extended beyond the apex of the parameres. Sclerite of the median lobe not expanded. Gonopore situated less than half of one gonopore width below the apex of the median lobe. Parameres symmetrical, with outer margins straight, with apex slightly inwardly curved and bluntly rounded. Basal piece long, ca. four-fifths the length of the parameres.

Etymology.

The species is named after the Berbice River in Guyana from where was collected. To be treated as a noun in apposition.

Distribution.

Known only from the type locality along the upper Berbice River in Guyana (Fig. 17 ).

Biology.

This species was collected in detrital leaf packs along the margin of the upper Berbice River (Fig. 22A ).

Figures

Figure 9. Dorsal view of heads of Chasmogenus spp. A C. amplius B C. acuminatus C C. berbicensis D C. clavijoi E C. undulatus F C. gato.

Figure 14. Aedeagi of (dorsal view) of Chasmogenus spp. A C. amplius B C. clavijoi C C. gato D C. berbicensis E C. brownsbergensis F C. schmits G, H C. guianensis G specimen from Suriname H specimen from Guyana. Scale bar: 0.25 mm.

Figure 17. Distribution of Chasmogenus spp.

Figure 22. Habitat of Chasmogenus spp in Guyana. A Type locality and habitat for C. berbicensis, Guyana, margin / detrital sandbar of the upper Berbice River (collecting event GY 14 - 0922 - 02 A) B type locality and habitat for C. undulatus Guyana, near Ayanganna airstrip (collecting event GY 14 - 0317 - 01 A) C habitat for C. acuminatus and C. guianensis, Guyana, small tributary of the upper Berbice River (collecting event GY 14 - 0924 - 01 A) D habitat for C. acuminatus (collecting event GY 13 - 1103 - 02 A).