Pterosthetops baini, 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 : 446-449

Pterosthetops baini sp. nov.

( Figs 3 A & 4A)

Type locality. South Africa, Western Cape, Witzenberg mountains, Michell’s Pass, wet rock face along R46 road, D.T. Bilton leg. ( Fig 5 B).

Type material. Holotype (male): “ September 2002 South Africa WC// Mitchell’s Pass nr. Ceres// madicolous seepages// D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( SAM).

Description. Size: Holotype: BL 2.1 mm; EL 1.35 mm; EW 0.85 mm. Dorsum ( Fig. 3 A) brown to black with a brassy greenish sheen on head, pronotum and elytra. Maxillary palpi pitchy brown, legs reddish brown; femora and tarsi darker than tibiae. Venter predominantly dark piceous, with silvery hydrofuge pubescence.

Head: Labrum transverse, strongly rounded at sides, with thickened anterior margin, and marked apicomedian emargination, running approx. 0.3 of length. Sides of apicomedian emargination distinctly raised. Surface of labrum dull, with well-marked microreticulation and moderately dense, short decumbent setae. Clypeus and much of frons and vertex with strong, punctulate microreticulation. Scattered decumbent setae towards front of clypeus and lateral areas of frons. Frons with a central elevation, broken by a slightly elongate shallow concavity between the large, shining ocelli, and arcuate sulci running from just in front of each ocellus towards the lateral corners of the frontoclypeal suture, opening onto clypeus. Elevated area of frons relatively smooth, with short decumbent setae, situated in irregular sockets/punctures. Frons and clypeus slightly raised and thickened anterior to eyes. Eyes large, occupying almost 0.5 of the lateral margins of the head; 12 convex facets in longest series.

Pronotum: Distinctly cordate, with strongly explanate sides. Anterior angles obtusely rounded. Sides crenulated, this crenulation being stronger anteriorly. Lateral margins weakly to sharply arcuate over anterior 0.75, then almost straight to rectangular posterior angles ( Fig. 3 A). Anterior margin almost straight, with very weak hyaline border in middle, which is scarcely visible. Posterior margin weakly bisinuate to centre. Entire upper surface finely microreticulate and coarsely punctate, each puncture with a short decumbent seta, as on head. Median longitudinal sulcus weak, very shallow, but foveate anteriorly and posteriorly; posterior fovea approx. 2x depth of shallower anterior fovea. Anterior fovea elongate; posterior more rounded. Sides of sulcus raised posteriorly and anteriorly. Anterior and posterior admedian fovea very shallow, open anteriorly. Adlateral fovea small, rounded and deep, opening somewhat anteriorly. Adlateral fovea deeper, particularly the posterior ones. Anterior and posterior adlateral fovea linked by a shallow channel.

Elytra: Elongate, with rounded shoulders and apex. Sides straight over approx. first 0.6, then rounded to apex. Broadest just 0.3 from apex. Explanate lateral margin narrow at shoulder, becoming wider towards apical third, and present to apex. Apices separately rounded. Each elytron 10-seriate punctate, and with small, shallow, transverse depression (saddle) close to middle, occupying intervals 2, and to a lesser extent 3–4. Punctures of elytral striae each bearing a small seta. Puncture rows 1–3 more irregular in saddle; more so on right elytron than left. Intervals raised, particularly towards elytral apex. Interval 8 more prominently raised than other intervals over most of its length. Each interval with a row of short, decumbent setae, these usually being situated on a small, apicallydirected tubercle. Entire elytral surface shining; lacking microreticulation.

Venter: Mentum rather shining, with strong, coarse microreticulation. Submentum shining, with very weak, obsolete, transverse microreticulation, and with scattered long decumbent setae. Genae with isodiametric microreticulation in front of weak transgenal ridges; transverse microreticulation behind. Gular with strong, fine transverse microreticulation. Pronotal hypomeron shining, lacking microreticulation, with scattered stout setae towards anterior margin. Prosternum finely rugose, with a very strong 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. 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 lacking microreticulation. Epipleurs narrow and ridge-like; shining. Abdominal ventrites 1–4 fringed with long, closely-set squamiform setae at hind margins. Ventrites 1–5 with relatively large triangular patches of hydrofuge setal vestiture anterio-laterally. 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. Ventrites shining. Central area of abdominal ventrites 1–4, and entire surface of ventrites 5 & 6 with shallow, open transverse microreticulation. Ventrites 5 & 6 with transverse row of long, adpressed hair-like setae, positioned 0.75 of the way down the sternite.

Aedeagus: Elongate, sinuous in lateral view, with parameres attached near base, and extending well beyond apex of main piece. Main piece characteristically shaped, with short, needle-like upturned ventrally directed process at apex. Distal lobe sinuous, curved strongly to the left in view, and extending below the apices of parameres ( Fig. 4 A).

Female: Unknown.

Differential diagnosis. Recognized by a combination of the shining elytra, which lack microreticulation, the short, single elytral saddle, and the punctate pronotal disc. Male genitalia characteristic (see Fig. 4 A).

Distribution. Known to date only the type locality, a wet rock face in Mitchell’s Pass in the Witzenberg in the Western Cape region ( Fig. 9 ).

Etymology. Named after Andrew Geddes Bain (1797–1864), geologist, road engineer, palaeontologist and explorer, who directed the construction of Mitchell’s Pass in 1848, inadvertently creating accessible habitat for Pterosthetops and other interesting water beetles.

Figures

FIGURE 3. Habitus of Pterosthetops holotypes. A) P. baini sp. nov.; B) P. pulcherrimus sp. nov.; C) P. tuberculatus sp. nov.; D) P. uitkyki sp. nov. Scale bar = 1 mm.

FIGURE 4. Aedeagi of Pterosthetops holotypes. A) P. baini sp. nov.; B) P. pulcherrimus sp. nov.; C) P. tuberculatus sp. nov.; D) P. uitkyki sp. nov. Scale bar = 0.5 mm.

FIGURE 5. Habitats of Pterosthetops species. A) Cederberg, seepage over sloping rock beside stream @ 1,200 m below Wolfberg Arch, beside Matjiesrivier-Wupperthal road— P. coriaceus sp. nov., P. hawequas, P. impressus; B) Witzenberg, Michell’s Pass, wet rock face along R 46 road - P. baini sp. nov., P. hawequas, P. impressus (arrow indicates larva of Aspidytes niobe Ribera, Beutel, Balke & Vogler, 2002); C) Cederberg, Uitkyk Pass, seepages over rock face beside road— P. harrisoni, P. hawequas, P. impressus, P. pulcherrimus sp. nov., P. tuberculatus sp. nov., P. uitkyki sp. nov.; D) Table Mountain, seepage over rock in Echo Valley— P. equestrius, P. impressus. Photos D T & R Bilton.

FIGURE 9. Distribution of Pterosthetops species in the Western Cape: closed white symbol P. baini sp. nov., blue symbol P. coriaceus sp. nov., green symbols P. harrisoni, open white symbols P. impressus, red triangle P. harrisoni, P. hawequas, P. impressus, P. pulcherrimus sp. nov., P. uitkyki sp. nov. & P. tuberculatus sp. nov. Basemap source: ESri, GigitalGlobe, GeoEye, i-cubed, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, Swisstopo and the GIS User Community.