Pterosthetops swartbergensis, Bilton, David T., 2014

Bilton, David T., 2014, New species and new records of Pterosthetops: eumadicolous water beetles of the South African Cape (Coleoptera, Hydraenidae), Zootaxa 3811 (4), pp. 438-462 : 444-446

Pterosthetops swartbergensis sp. nov.

( Figs 1 C & 2C)

Type locality. South Africa, Western Cape, Groote Swartberg mountains, seepages on sloping rock face beside R328 road, north of Swartberg pass, 2 km N of junction with Gamkaskloof road, D.T. Bilton leg. ( Fig. 7 A).

Type material. Holotype (male): “ 24/ix/2009 South Africa WC// Groote Swartberg seepages on// Rock faces beside R328 road 2 km // N of junction with De Hell track// D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( SAM).

Paratypes (2): South Africa: 2 ♀ “ 24/ix/2009 South Africa WC// Groote Swartberg seepages on// Rock faces beside R328 road 2 km // N of junction with De Hell track// D T Bilton leg.” ( CDTB, SANC). All with red paratype labels.

Description. Size: Holotype: BL 2.2 mm; EL 1.4 mm; EW 0.85 mm. Paratypes: ♀s BL 2.25–2.45 mm; EL 1.5–1.55 mm; EW 0.85–0.9 mm. Dorsum ( Fig. 1 C) dark brown to black with a brassy metallic sheen on head, pronotum and elytra. Maxillary palpi pitchy to black, legs dark chestnut brown; femoro-tibial junctions and tarsi darker. Venter predominantly dark piceous, with silvery hydrofuge pubescence.

Head: Labrum transverse, with thickened anterior margin, and marked apicomedian emargination, running approx. 0.5 of length. Sides and apices of apicomedian emargination distinctly raised. Surface of labrum dull, with well-marked microreticulation and stout decumbent white setae around apical and lateral margins. Frontoclypeal suture weak but visible. Clypeus, frons and vertex, with strong, punctulate microreticulation; deeper towards lateral margins of frons and on vertex. Small patches on central vertex in front of ocelli smoother, with scattered larger punctures. Ocelli large; shining. Scattered stout, decumbent setae, particularly towards lateral margins of frons. Frons with a central elevation, broken by a slightly elongate concavity between the well-marked, shining ocelli, and arcuate sulci running from just in front of each ocellus towards the lateral corners of the frontoclypeal suture, opening onto clypeus. Frons and clypeus with weakly raised and thickened lateral margins in front of eyes. Eyes large, occupying slightly less than 0.5 of the lateral margins of the head; 11 convex facets in longest series.

Pronotum: Distinctly cordate, relatively flat, with strongly explanate sides. Anterior angles obtusely rounded. Sides weakly crenulated and weakly to sharply arcuate over anterior 0.75, then almost straight to rectangular posterior angles ( Fig. 1 C). Anterior margin almost straight, with very weak hyaline border in middle, which is scarcely visible. Posterior margin very weakly bisinuate to centre. Upper surface, with the exception of raised areas between posterior coarse punctures, with very weak, isodiametric microreticulation; meshes transverse towards anterior and posterior margins. Median longitudinal sulcus shallow, foveate anteriorly and posteriorly; posterior fovea approx. 2x depth of anterior fovea. Anterior fovea elongate; posterior more rounded. Sides of sulcus raised posteriorly and anteriorly. Anterior admedian fovea shallow, transverse and open towards the front and sides. Posterior admedian fovea deeper, elongate, well-marked and orientated anteriolaterally. Adlateral fovea small, rounded and deep, opening somewhat anteriorly. Posterior adlateral fovea deeper than anterior ones. Front and rear of pronotal disc with transverse fields of coarse, setose punctures, most bearing a small flat, decumbent seta. Punctures becoming larger towards posterior margin, and somewhat confluent close to anterior margin. Lateral and central areas of pronotum with short decumbent setae; anterior rims of setal sockets elevated.

Elytra: Elongate, with rounded shoulders and apex. Sides straight and parallel-sided in middle 0.3; rounded to apex in apical 0.3. Broadest just behind middle. Narrow explantae lateral margin present from just behind shoulder to apex. Apices truncately rounded. Each elytron 10-seriate punctate, and with a shallow, transverse depression (saddle) just behind middle, occupying intervals 2–4. Punctures of elytral striae each bearing a small seta. Puncture rows 1–2 more irregular in saddle. Intervals 1–9 weakly raised outside saddle region. Each interval with a row of short, decumbent setae, these usually being situated on a small, apically-directed tubercle. Entire elytral surface shining; lacking microreticulation.

Venter: Mentum rather shining, with open microreticulation. Submentum also shining, with weaker microreticulation. Genae with strong isodiametric microreticulation in front of weak transgenal ridges; more transverse towards sides and rear. Gular region with fine, slightly transverse microreticulation. Pronotal hypomeron shining, finely wrinkled, with scattered stout setae towards anterior margin. Prosternum finely rugose, with a wellmarked central ridge, and distinct hydrofuge vestiture, particularly towards lateral margins. Meso and metaventrites with well-developed squamose hydrofuge vestiture; vestiture shorter and less dense towards lateral and hind margins. Mesoventral plaques visible, glabrous, but dull, forming an inverted Y. Border between mesoventrite and anepisternum 2 marked by a glabrous ridge. Metaventrite with distinct longitudinal depression over rear 0.6 of sternite; depression of even depth—not foveate. Elytral pseudepipleurs shining and finely wrinkled. Epipleurs narrow and ridge-like; shining. Abdominal ventrites 1–4 fringed with long, closely-set squamiform setae at hind margins. Ventrites 1–5 with a triangular patch of hydrofuge setal vestiture anteriolaterally. Ventrite 1 also with hydrofuge setae below hind coxae, and narrowly along much of anterior margin; these setae resembling those on lateral and hind margins of metaventrite. Central area of ventrites 1–4 smooth lacking microreticulation in centre, but with traces of fine, open, transverse microreticulation on sides, just inside areas with vestiture. Ventrites 5 & 6 with transverse row of long, adpressed hair-like setae, positioned 0.75 of the way down the sternite. Ventrite 5 with fine, open transverse microreticulation anterior to the setal row; strong transverse microreticulation posterior to it. Ventrite 6 with open transverse microreticulation throughout.

Aedeagus: Elongate, sinuous in lateral view, with parameres attached near base, and extending well beyond apex of main piece. Main piece characteristically shaped, with long, ventrally-directed apical process, resembling a bird’s beak, this being located towards the left of the centre in ventral view. Distal lobe elongate and sinuous, curved in lateral and ventral view, and extending slightly beyond apices of parameres ( Fig. 2 C).

Female: Microreticulation on head and pronotum somewhat stronger than that seen in the male.

Variation: One of the female paratypes has the arcuate sulci on the head more strongly marked and pit-like at the base.

Differential diagnosis. Recognized by a combination of the shining elytra, which lack microreticulation, the short, single elytral saddle, the strong microreticulation and lack of distinct punctures on the pronotal disc and (compared to Pterosthetops indwei sp. nov), the relatively flat pronotum with shallower sulcus and fovea. Male genitalia characteristic; differing from P. indwei sp. nov. in the shape of the apex of the main piece, and the attachment site of the apical process (see Fig. 2 C).

Distribution. Known to date only from the type locality, a seasonally wet rock face in the Groote Swartberg range of the Western Cape region ( Fig. 8 ).

Etymology. Named after the Swartberg mountain range.

Figures

FIGURE 1. Habitus of Pterosthetops holotypes. A) P. coriaceus sp. nov.; B) P. indwei sp. nov.; C) P. swartbergensis sp. nov. Scale bar = 1 mm.

FIGURE 2. Aedeagi of Pterosthetops holotypes. A) P. coriaceus sp. nov.; B) P. indwei sp. nov.; C) P. swartbergensis sp. nov. Scale bar = 0.5 mm.

FIGURE 7. Habitats of Pterosthetops species. A) Swartberg, seepage on sloping rock face beside R 328 road, north of Swartberg Pass, 2 km N of junction with Gamkaskloof road— P. br i nc k i, P. swartbergensis sp. nov. Seepage dry, January 2014; B) Cederberg, seepage at top of Uitkyk pass— P. hawequas, P. tuberculatus sp. nov. C) Cederberg, view from summit of Uitkyk Pass. Photos D T Bilton & A Foggo.

FIGURE 8. Distribution of Pterosthetops species in the Western Cape: red symbols P. br i nc k i, green symbols P. equestrius, yellow symbols P. hawequas, white symbols P. indwei sp. nov., blue symbol P. swartbergensis sp. nov. Basemap source: ESri, GigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, Swisstopo and the GIS User Community.