Chasmogenus brownsbergensis, 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 brownsbergensis sp. nov. Figures 10A , 14E , 17 , 21A

Type material.

Holotype (male): "Suriname: Brokopondo District/ 04°56.871'N, 55°10.911'W, 462 m/ Brownsberg Nature Park, forested/ stream with lots of detritus; leg./ Short, Maier, McIntosh; 4.viii.2012/ SR12-0804-01A", "[barcode]/SEMC1114121/ KUNHM-ENT" "HOLOTYPE/ CHASMOGENUS/ brownsbergensis sp. n./ des. Smith & Short" (NZCS). Paratypes (46): Suriname: Brokopondo District: same data as holotype except: 4.viii.2012, pools in road, SR12-0804-03A (20 exs., SEMC, including DNA Voucher SLE1828); Brownsberg Nature Park, trail between Park HQ and Mazaroni Val, 4°56.934'N, 55°10.825'W, 467 m, 20.iii.2017, leg. Short et al., pools in dirt road, SR17-0320-02A (18 exs., SEMC, NZCS); same data as previous except: 22.iii.2017, SR17-0322-01A (8 exs., SEMC, including DNA Voucher SLE1861).

Differential diagnosis.

Among smaller species with a broadly rounded clypeal emargination, this species is similar in size, morphology, and general form of the aedeagus as C. guianensis , but can be distinguished by the coloration of the head which has mesal dark patches on the clypeus and labrum (Fig. 10A ) in contrast to the typical bicolored or uniform coloration of the head. In addition, the apex of the median lobe of the aedeagus is ca. the same level as the apex of the parameres. In C. guianensis , the apex of the median lobe is shorter than the apex of the parameres.

Description.

Size and color. Total body length 3.7-3.8 mm. Body form elongate oval with slightly curved lateral margins. Dorsum of head bicolored, frons very dark brown, labrum and clypeus dark orange-brown (Fig. 10A ). Darker patches on mesal portions of clypeus and labrum (Fig. 10A ). Elytra uniformly dark brown. Venter dark orange-brown centrally, dark brown marginally. Head. Ground punctation on head moderately coarse. Clypeus with anteromedial emargination, which exposes a wide smoothly rounded gap between labrum and clypeus (Fig. 10A ). Mentum strongly 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 moderately coarse. Prosternum even, not tectiform. Mesoventrite with very weak elevation forming a thin posteromedial longitudinal carina. Metafemora densely pubescent in basal nine-tenths. Aedeagus. Aedeagus (Fig. 14E ) with median lobe widest at base and very slightly tapering until the apical fifth, then narrowing to form an acute triangular apex which is even with the apex of the parameres. Sclerite of the median lobe not expanded. Gonopore situated ca. half of one gonopore width below the apex of the median lobe. Parameres symmetrical, with outer margins straight, with apex inwardly curved, tapered, and bluntly rounded. Basal piece of medium length, ca. two-thirds the length of the parameres.

Etymology.

The species is named after Brownsberg Nature Park, the only locality where it is currently known. To be treated as a noun in apposition.

Distribution.

This species is only known from Brownsberg Nature Park in Suriname (Fig. 17 ).

Biology.

Long series of this species were collected from pools in dirt roads in Brownsberg Nature Park. The pools are large, and often contain detritus as they are through forested areas (Fig. 21A ). One specimen was collected in a forested stream with lots of detritus.

Figures

Figure 10. Dorsal view of heads of Chasmogenus spp. from Suriname and Guyana A C. brownsbergensis B C. ligulatus C C. guianensis D C. pandus.

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).