Parasthetops porcellus, Bilton, David T., 2017

Bilton, David T., 2017, Water beetles from the Bokkeveld Plateau: a semi-arid hotspot of freshwater biodiversity in the Northern Cape of South Africa, Zootaxa 4268 (2), pp. 191-214 : 195-201

Parasthetops porcellus sp. nov. ( Figs 2–6 )

Type locality. South Africa, South Africa Northern Cape, Bokkeveld Plateau, Avontuur Reserve , Grasberg River below Fynbos Cottage , 765m 31 16 14.67S 19 0 2 53.02E ( Fig. 6 A–B).

Type material. Holotype (male): “ 6/x/2015 South Africa NC// Avontuur Reserve—temporary // stream below Fynbos Cottage // 765m 31 16 14.67S // 19 0 2 53.02E D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( AMG) .

Paratypes (28): 13 ♂, 11 ♀ same data as holotype ; 1 ♂, 1♀ “ 6/x/2015 South Africa NC// Avontuur Reservepools in drying// temporary stream 795m 31 17 38.92S // 19 0 1 12.03E D T Bilton leg.” ; 1 ♀ “ 6/x/2015 South Africa NC// Avontuur Reserve—margins of// Kromvlei 799m 31 18 15.58S // 19 0 0 51.42E D T Bilton leg.” ; 1♂ “ 7/x/2015 South Africa NC// Oorlogskloof Canyon—wet rock faces below Driefontein // Waterfall, 640m, 31 30 41.85S // 19 0 6 58.98E D T Bilton leg.” All with red paratype labels ( AMG, CDTB, MCZ, NMW, SAM, SANC, TMSA).

Description. Size: Holotype: BL 2.25 mm; EL 1.35 mm; EW 0.90 mm. Paratypes: ♂ s BL 2.15–2.30 mm; EL 1.35–1.45 mm; EW 0.85–0.90 mm. ♀ s BL 2.10–2.35 mm; EL 1.35–1.45 mm; EW 0.85–0.90 mm.

Colour: Dorsum ( Fig. 2 A) brown to black, with greenish metallic reflections on head, pronotum and elytra. Maxillary palpi brown to black, darkest on apical segment. Legs yellowish brown; femorotibial junctions and tarsi infuscated. Venter brown to black; head and prothorax paler than meso and metathorax and abdominal ventrites.

Head: Labrum transverse, widening anteriorly. Rounded apicolaterally with shallow, broad apicomedian emargination running approx. 0.15 of length. Anterior margin and sides of apicomedian emargination strongly raised. Prominent ridge present inside lateral and posterior margins of labrum. Surface weakly shining, with shallow, isodiametric microreticulation and medium punctures bearing white decumbent setae. Clypeus weakly shining, with isodiametric microreticulation, meshes smaller and more strongly impressed laterally; with close, coarse punctation, each puncture bearing a white decumbent seta. Frontoclypeal suture strong, arcuate. Frons weakly shining, with isodiametric microreticulation, meshes smaller and more impressed laterally; close, coarse punctures as on clypeus. Anteocellar sulci strong, deeper posteriorly and opening anteriorly close to frontoclypeal suture; strongly microreticulate and punctate, head similarly sculptured between sulci and compound eyes. Ocelli shining, rather flat. Compound eyes relatively large, occupying 0.4 lateral margin of head, 14 ommatidia in longest series.

Pronotum: Cordate, transverse, broadest just behind middle. Anterior margin arcuate over median 0.3, without hyaline border; posterior margin bisinuate around centre. Anterior angles broadly rounded, posterior angles slightly obtuse, prominent. Lateral margins sinuated from widest point to base, broadly marginated and strongly crenulated. Surface weakly shining, with strong isodiametric microreticulation throughout and moderate to close, coarse punctures. Punctures deeper close to anterior and posterior margins. Punctures on disc bearing white decumbent setae of varying length, those on lateral areas with either long, white recumbent setae or short, white peg-like setae. Microreticulation strongest close to lateral margins, rugulose. With 10 distinct foveae as follows: Anterior median fovea elongate, deepest in centre; posterior median fovea shallow, rounded. Anterior admedian foveae shallow, transverse, opening laterally; posterior admedian foveae short, oval, orientated anteriolaterally. Anterior and posterior adlateral foveae small, rounded, pit-like.

Elytra: Elongate oval, broadest at middle. Subparallel over middle 0.6, then attenuated to truncately rounded apex; weakly emarginated at suture. Lateral margins moderately explanate. Punctures of elytral series evident to apex; series striate impressed, particularly on disc, less so posteriorly. Serial punctures shallow, with white decumbent setae just reaching next puncture in row. Intervals with irregular row of punctures bearing long, white recumbent-decumbent setae. Intervals 2–4 relatively broad and flat anteriorly, approx. 3x width of adjacent serial punctures; randomly punctured in basal 0.5. Interval 6 raised for 0.1 behind shoulder; intervals 7–8 raised for 0.2 behind middle. Surface weakly shining, with fine, shallow microreticulation; scattered meshes with aeneous reflection throughout.

Legs: Apical protarsomere with two stout ventral setae; basal three protarsomeres with suction setae.

Venter: Mentum shining, with shallow isodiametric-transverse microreticulation and moderate, fine punctures bearing stout decumbent setae. Long recumbent setae on anterior margin. Submentum shining, with shallow transverse microreticulation and sparse, medium punctures bearing decumbent setae. Genae shining, with strong, transverse microreticulation. Gula shining; microreticulation less transverse and less strongly impressed than on genae. Prosternum with strong central ridge, surface rugulose with dense hydrofuge vestiture. Pronotal hypomeron broad, with shallow, isodiametric microreticulation. Meso and metaventrite with dense hydrofuge vestiture. Metaventral plaques weak, forming an inverted Y; stem 0.25 length of arms; low admedian and adlateral ridges also present. Metaventrite with broad, shallow median fovea over posterior 0.5; fovea with hydrofuge vestiture but with small, shining, triangular glabrous patch present at apex, between metacoxae. Elytral pseudepipleurs shining, weakly microreticulate, attenuated from middle to apex of abdominal ventrite 5. Elytral epipleurs shining, narrow. Abdominal ventrites 1–5 with dense hydrofuge vestiture. Abdominal ventrites 1–4 with closely-set squamiform setae at hind margins. Abdominal ventrite 5 with irregular row of long, white decumbent setae in lateral 0.3, close to posterior margin. Abdominal ventrite 6 glabrous, shining, with isodiametric-slightly transverse microreticulation and medium, coarse, irregular punctures in posterior 0.5, bearing long, yellowish decumbent setae.

Aedeagus: Elongate, distinctly angled in ventral and lateral views, with parameres attaching close to base. Parameres asymmetrical; right paramere longer than left in ventral view, extending just beyond apical projection of main piece. Main piece relatively broad in ventral view, with stout apical tooth, and long, coiled, tube-like distal lobe, extending far beyond paramere apices ( Fig. 3 A).

Female: Elytra broader and more strongly explanate along lateral margins than in males; explanate margin reaching apicolateral angle, where it is very pronounced; pseudepipleurs extends to apex. Abdominal ventrite 6 glabrous, shining, with shallow isodiametric microreticulation; apical 0.5 with medium punctures bearing short, stout yellowish recumbent-decumbent setae.

Variation: In addition to size, paratypes vary somewhat in dorsal microreticulation, some specimens with this very weak on the centre of the frons. In some specimens the elytra are slightly attenuated in the centre, between the meso and metacoxae. The elytra of some specimens are paler brown than in the illustrated holotype, although this may, in part, be due to slight tenerality.

Differential diagnosis. A member of the nigritus group sensu Perkins & Balfour-Browne (1994), with elytral intervals 2–4 relatively broad and irregularly punctured and short, dense, spine-like setae on female abdominal ventrite 6. The new species would key to P. nigritus Perkins & Balfour-Browne, 1994 , from which it can be readily distinguished by the more strongly microreticulate pronotal reliefs, microreticulate elytral intervals, and distinctive aedeagus.

Distribution. To date known from the Bokkeveld Plateau, close to Neiuwoudtville. Here it was found in range of running and standing water habitats (Sites 5 & 7–9), where it was sometimes very abundant, many more specimens being observed than were collected.

Etymology. From the latin porcellus (= little pig, piglet), in reference to the coiled distal lobe of the aedeagus, which somewhat resembles the tail of a pig.

Figures

FIGURE 2. Habitus of hydraenid holotypes. A) Parasthetops porcellus sp. nov.; B) Mesoceration castaneum sp. nov.; C) M. chasmum sp. nov.; D) M. sabulosum sp. nov.

FIGURE 3. Aedeagi of hydraenid holotypes, ventral and lateral views. A) Parasthetops porcellus sp. nov.; B) Mesoceration castaneum sp. nov.; C) M. chasmum sp. nov.; D) M. sabulosum sp. nov.

FIGURE 4. Habitats on the Bokkeveld Plateau. A) Plateau margin close to Kromvlei on Avontuur Reserve, emphasising isolation from Knersvlakte below; B) Avontuur Reserve, vernal pools on clay (Site 6); C) Vernal pool on sand ca. 1 km E of Vanrhyn’s Pass (Site 4); D) Vernal pool on sand / silt ca. 2 km E of Vanrhyn’s Pass (Site 1). Photos D. T. & R. Bilton.

FIGURE 5. Habitats on the Bokkeveld Plateau. A) Avontuur Reserve, margins of Kromvlei (Site 8); B) Avontuur Reserve, pools in drying stream (Site 7); C) Oorlogskloof Reserve, wet rocks & stream below Driefontein Waterfall (Sites 9 & 10; stream below large boulders in photo); D) Oorlogskloof Reserve, wet rocks below Driefontein Waterfall (Site 9 — with Andy Foggo). Photos D. T. Bilton.

FIGURE 6. Habitats on the Bokkeveld Plateau. A – B) Avontuur Reserve, stream below Fynbos Cottage (Site 5); B) C) Oorlogskloof Reserve, Oorlogskloof River below Driefontein Waterfall (Site 11) Photos D. T. Bilton.