Chasmogenus schmits, 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 schmits sp. nov. Figures 14F , 17 , 21D

Chasmogenus sp. X Short & Kadosoe, 2011: 87 (in part).

Type material.

Holotype (male): "Suriname: Sipaliwini District/ 2°10.521'N, 56°47.244'W, 228 m/ on Kutari River; leg. Short/ & Kadosoe; forested swamp/ 19.viii.2010; SR10-0819-01A/ Camp 1; 2010 CI-RAP Survey"/ "[barcode] SEMC0914251/KUNHM-ENT", "HOLOTYPE/ CHASMOGENUS/ schmits sp. n./ des. Smith & Short", "DNA VOUCHER/ Extraction #/ SLE-1824" (NZCS). Paratypes (2): Suriname: Sipaliwini: same data as holotype (2 exs., SEMC).

Differential diagnosis.

This species is similar morphologically to C. clavijoi , but the median lobe emarginates laterally to a greater degree and is only as wide as one paramere basally (Fig. 14F ), whereas the median lobe is ca. 1.5 × the width of one paramere basally in C. clavijoi . The apices of the parameres are also more squarely blunted rather than roundly curved. Examination of the aedeagus is the only way to definitively identify this species. Unassociated females may not be determined with certainty.

Description.

Size and color. Total body length 4.3 mm. Body form elongate oval with slightly curved lateral margins. Dorsum of head dark brown, labrum distinctly paler. Pronotum and elytra uniformly dark brown. Venter dark orange-brown. Head. Ground punctation on head fine. Clypeus with anteromedial emargination which exposes trapezoidal gap between clypeus and labrum. Mentum moderately depressed in anterior half with triangular 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 and uniformly pubescent in basal nine-tenths. Aedeagus. Aedeagus (Fig. 14F ) with median lobe widest at base, appearing weakly constricted medially, then narrowing abruptly in the apical fifth to form an acute triangular apex which is slightly below the apex of the parameres. Sclerite of the median lobe not expanded. Gonopore situated less than a third 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.

Named in honor of Sarah C. Schmits, a longtime member of the Short Lab who has provided invaluable support to advance and disseminate knowledge of aquatic beetles.

Distribution.

Known only from the type locality in Suriname (Fig. 17 ).

Biology.

This species was collected from a forested swamp habitat (Fig. 21D ).

Figures

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 21. Habitat of Chasmogenus spp in Suriname. A Type locality and habitat for C. brownsbergensis, Brownsberg Nature Park (collecting event SR 12 - 0804 - 03 A) B type locality and habitat for C. ligulatus, near Mt. Kasikasima (collecting event SR 12 - 0320 - 02 A) C type locality and habitat for C. tafelbergensis, summit of Tafelberg tepui (collecting event SR 13 - 0817 - 01 A) D type locality and habitat for C. schmits, S of Kwamala along the Kutari River (collecting event SR 10 - 0316 - 01 B) E habitat for C. acuminatus, Central Suriname Nature Reserve, Raleighvallen (collecting event SR 16 - 0316 - 01 B) F habitat for C. guianensis, upper Palumeu River, (collecting event SR 12 - 0311 - 01 A).