Review of the genus Chasmogenus Sharp, 1882 of northeastern South America with an emphasis on Venezuela, Suriname, and Guyana (Coleoptera, Hydrophilidae, Acidocerinae) Author Smith, Rachel R. Department of Ecology & Evolutionary Biology, and Division of Entomology, Biodiversity Institute, University of Kansas, Lawrence, KS 66045, USA rr.smith816@gmail.com Author Short, Andrew Edward Z. Department of Ecology & Evolutionary Biology, and Division of Entomology, Biodiversity Institute, University of Kansas, Lawrence, KS 66045, USA aezshort@ku.edu text ZooKeys 2020 934 25 79 http://dx.doi.org/10.3897/zookeys.934.49359 journal article http://dx.doi.org/10.3897/zookeys.934.49359 1313-2970-934-25 B9F2C8D8C0314191B6F51E78D4D6881E 598339B5A93C5551BC575CD4048FC8D3 Chasmogenus bariorum Garcia , 2000 Figures 3D-F , 6 , 7A , 8C , 11A-H , 17 , 19A-C , 19E, F Chasmogenus bariorum Garcia , 2000: 49. Synonyms. Chasmogenus occidentalis Garcia , 2000, syn. nov. Type material examined: Holotype (male): "Venezuela, Zulia/Mcpio. Machique de/ Perija, El Tokuku,/300 msnm 03/V/1998", "Colectores:/M. Garcia" , "[Barcode]/ MALUZ10150/ LUZ-Venezuela", "Holotipo ['male symbol' / Chasmogenus / occidentalis / Dcrip. M. Garcia , 1999" (MALUZ). The date on the label of the holotype (Fig. 6 ) differs slightly from that given in the original description, which was listed as 2 May 1995 instead of 3 May 1998. The type is an undissected male, the aedeagus is visibly protruding from the abdomen. We also examined a permanent genitalia slide that had been presumed to be the holotype and is labeled as this species (Fig. 11B ). Chasmogenus yukparum Garcia , 2000, syn. nov. Type material examined: Holotype (male): "Venezuela, Zulia/Mcpio. Machique de/ Perija, El Tokuku,/300 msnm 03/V/1998", "Colectores:/M. Garcia" , "[Barcode]/ MALUZ10149/ LUZ-Venezuela", "Holotipo ['male symbol' / Chasmogenus / yukparum / Dcrip. M. Garcia , 1998" (MALUZ). The date on the label of the holotype (Fig. 6 ) differs slightly from that given in the original description, which was listed as 5 May 1995 instead of 3 May 1998. The dorsal portion of the abdomen is missing and may be the result of dissection. We also examined a permanent genitalia slide which is labeled as this species and had been presumed to be the holotype (Fig. 11C ). The description of this species was based on a single male so we assume the genitalia on the slide is the holotype. Figure 7. Lateral view of mesoventrite. A C. bariorum B C. cuspifer . Scale bar: 0.10 mm. Type material examined. Holotype (male) : "Venezuela, Zulia/Mcpio. Machique de/ Perija, El Tokuku,/300 msnm 03/V/1998", "Colectores:/M. Garcia" , "[Barcode]/ MALUZ10148/ LUZ-Venezuela", "Holotipo ['male symbol' / Chasmogenus / bariorum / Dcrip. M. Garcia , 1998" (MALUZ). The date on the label of the holotype (Fig. 6 ) differs slightly from that given in the original description, which was listed as 2 May 1995 instead of 3 May 1998. The type is an undissected male, the aedeagus is visibly protruding from the abdomen. We also examined a permanent genitalia slide that had been presumed to be the holotype and is labeled as this species (Fig. 11A ). 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 . Additional material examined (198). Venezuela: Aragua : Henri Pittier National Park, Rio La Trilla, 10.37319°N , 67.74250°W , 295 m, 4.i.2009, Short, Miller, Camacho, & Garica [sic], pools, VZ09-0104-01A (25 exs., MIZA, SEMC, including DNA Vouchers SLE078 and SLE531); Henri Pittier National Park, Rio Cumboto, 10.39376N , 67.79597W , 130m, 4.i.2009, leg. Short, Garcia , & Miller, riverside pools, VZ09-0104-02B (7 exs., SEMC); Henri Pittier National Park, 10°21.017'N , 67°40.883'W , 5.i.2009, leg. Miller, Camacho, and Garcia , small stream, VZ09-0105-01A (1 ex., SEMC). Guarico : Rio San Antonio, north of Dos Caminos, 9°46.320'N , 67°21.177'W , 280 m, 8.i.2009, leg. Short, Miller and Garcia , river margins, VZ09-0108-02A (7 exs., SEMC); same as previous except: leg. Miller & Short, side stream, VZ09-0108-02B (8 exs., SEMC, including DNA Voucher SLE1613); same as previous except: leg. K. B. Miller, micro habitats, VZ09-0108-02C (2 exs., SEMC); Stream at road crossing, north of Palenque, 9°6.794'N , 66°59.595'W , 152m, 8.i.2009, leg. Short, Garcia , Miller, Camacho and Joly, stream, VZ09-0108-03X (3 exs, SEMC); Rio Guarico , N. San Juan, 9.95788N , 67.37773W , 435 m, 8.i.2009, leg. K. Miller & L. Joly, along river, VZ09-0108-01X (5 exs., SEMC); ~15 km south of San Juan, 9°46.321'N , 67°21.201'W , 255 m, 3.i.2006, leg. A. E. Z. Short, stream margin and rock pools, AS-06-005 (1 ex., SEMC); ~20 km north of Dos Caminos, 9°44.034'N , 67°19.003'W , 225 m, leg. A. E. Z. Short, gravelly margin of river, AS-06-020 (24 exs., SEMC). Falcon : Rio Ricoa near Dos Bocas, 11°17.424'N , 69°26.061'W , 170 m, 9.vii.2009, leg. Short, Sites, Gustafson, Garcia , Camacho, and Inciarte, along river margins, VZ09-0709-02A/L-1063 (4 exs., SEMC). Lara : Rio Salado west of Arenales, 10°9.260'N , 69°57.458'W , 490 m, 22.i.2009, leg. Short, Garcia , and Camacho, gravel stream, VZ09-0122-01X (5 exs., SEMC). Trujillo : Rio Jirajara near Sabana Grande, 9°42.307'N , 70°32.570'W , 199 m, 29.i.2012, leg. Short, Arias, and Gustafson, muddy pool in floodplain, VZ12-0129-02A (4 exs., SEMC). Zulia : Perija National Park Tukuko, Rio Manantial, 9°50.490'N , 72°49.310'W , 270 m, 29.i.2009, leg. Short, Garcia , and Camacho, gravel margin, VZ09-0129-01A (13 exs., SEMC, including DNA Voucher SLE534); same data as previous except: 22.ix.2007, leg. A. E. Z. Short, rock pools/margins, AS-07-020b (27 exs., SEMC); same data as previous except: 16.vii.2008, leg A. Short, margins and pools, AS-08-027 (14 exs., SEMC); Perija National Park, Rio Tukuko, 09°50.515'N , 72°48.334'W , 15.vii.2008, leg. A. E. Z. Short, upstream of Tukuko, AS-08-029 (1 ex., 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 (5 exs., SEMC); same data as previous except: 28.i.2009, leg. A. Short, detrital pool, VZ09-0128-01A (3 exs., SEMC); c. 15 km southwest of El Dibujo, 10.79307N , 72.32331W , 155 m, 30.xii.2008, leg. Short, Garcia , and Camacho, muddy puddle, VZ08-1230-03B (1 ex, SEMC); same data as previous except: in stream, VZ08-1230-03X (2 exs., SEMC); Marshy pond, 10.85498N , 72.30837W , 81 m, 30.xii.2008, leg. Short, Garcia , and Camacho, pond margin, VZ08-1230-02X (1 ex., SEMC); 15 km west of Machiques, 10°02.962'N , 72°42.615'W , 432 m, 31.xii.2005, leg. A. E. Z. Short, isolated rock pool, AS-06-002 (1 ex., SEMC); Quebrada Riencito, 10.86041N , 72.32210W , 95 m, 30.xii.2008, leg. A. Short and M. Garcia , along margin, VZ08-1230-01B (34 exs., MIZA, SEMC). Differential diagnosis. This species may be easily distinguished from others in the region by mesoventrite raised into an acute tooth (Fig. 7A ), shared only with the sympatric C. cuspifer . Chasmogenus bariorum can be separated from C. cuspifer by its larger size (≥ 3.5 mm) and narrower apex of the median lobe (11A-H). Description. Size and color. Total body length 3.5-3.7 mm. Body form elongate oval with slightly subparallel lateral margins. Dorsum of head very dark brown to black, anterior margin of labrum slightly paler in color (Fig. 8C ). Pronotum dark brown, distinctly paler at anterior and lateral margins; elytra dark brown, slightly paler at posterior margins (Fig. 3D ). Prosternum and abdominal ventrites dark brown; meso- and metaventrites dark red-brown, trochanters and glabrous portion of femora red-orange (Fig. 3F ). Head. Ground punctation on head fine. Clypeus with anteromedial emargination, which exposes a trapezoidal-shaped gap between clypeus and labrum (Fig. 8C ). Mentum weakly depressed in anterior half with shallowly rounded anteromedial notch. Maxillary palps long, longer than width of head immediately posterior to eyes. Thorax. Ground punctation of pronotum fine. Prosternum moderately tectiform. Mesoventrite with median longitudinal carina, which is elevated into an acute tooth medially (Fig. 7A ). Metafemora densely pubescent with long golden setae in basal four-fifths (Fig. 3F ). Aedeagus. Aedeagus (Fig. 11A-H ) with outer margins of median lobe straight and parallel sided, with apex in the form of an acutely pointed triangle, which distinctly extends 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 slightly curved along entire length, appearing weakly convex; apex bifid, with outer and inner lobes subequal in height but with inner lobe usually narrower. Basal piece long, subequal to the length of the parameres. Distribution. Venezuela (Aragua, Falcon , Guarico , Lara, Trujillo, Zulia) (Fig. 17 ). Biology. Nearly all specimens are associated with the margins or side pools of streams and small rivers in the foothills of various Andean regions of Venezuela up to elevations of ca. 500 m. (Fig. 19A-C , 19E, F ) Remarks. Garcia (2000) described three species from the Rio Manantial, a small forested stream near Tokuko in the Serrania de Perija in northwestern Venezuela. We compared the holotypes of C. bariorum , C. occidentalis , and C. yukparum and determined they are conspecific. Because all three were described in the same publication, we here select C. bariorum as the valid name based on the principal of first reviser. The shape of the mesoventral tooth was used as a primary character to separate these three species but after examining specimens from a variety of localities we found this character to be variable. The presence of only a single species despite the variability of this feature is also supported by genetic data (Fig. 1 ). In his species descriptions, Garcia (2000) further differentiates C. yukparum from C. bariorum and C. occidentalis by indicating that the former has asymmetrical mandibles, while the latter two exhibit symmetrical mandibles; however, in the identification key this character is reversed, with the mandibles of C. occidentalis being described as asymmetrical while those of C. yukparum are symmetrical. Regardless, we examined the mandibles in the three holotypes and found no substantial difference in mandibular symmetry; all three types have bifid mandibles with minor variation in the size of the teeth, as with many of the other specimens we examined. There appears to be some confusion with regard to the genitalia slides associated with the holotypes. In Garcia (2000) , the caption of fig. 3 indicates all illustrated genitalia are of the holotypes. However, this is not possible as some of the labeled holotypes are undissected males. Because C. yukparum was described from a single male and its abdomen is partially missing, we presume the genitalia slide associated with the holotype is in fact the holotype. However, we are uncertain of which exact specimens should be associated with the "type" genitalia slides of C. bariorum and C. occidentalis . Regardless, this uncertain association does not impact any of our conclusions regarding their synonymy: it is clear that all three genitalia slides represent a single species ( C. bariorum ) and that all three male holotype specimens represent the same conspecific species as those on the slides.