Pterosthetops tuberculatus, 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 : 451-452

Pterosthetops tuberculatus sp. nov.

( Figs 3 C & 4C)

Type locality. South Africa, Western Cape, Middelberg mountains, wet rock face along R303 road in Middelberg Pass above Blinkwater, D.T. Bilton leg. ( Fig 6 A).

Type material. Holotype (male): “ 20/ix/2010 South Africa WC// Middelberg Pass on 303 road// above Blinkwater—seepages with algae// D.T. Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( SAM).

Paratypes (29): South Africa: 4 ♂, 4 ♀ “ 20/ix/2010 South Africa WC// Middelberg Pass on 303 road// above Blinkwater—seepages with algae// D.T. Bilton leg.” ( CDTB, NMW); 1 ♂ “ Sept. 2002 South Africa WC// Bainskloof Pass above// Wellington—seeps on rockface// D.T. Bilton leg.” ( SANC); 1 ♂ [lacking head] “ Sept. 2002 South Africa WC// Cederberg seeps along R364// Ca. 20 km E of Clanwilliam// D.T. Bilton leg.” ( CDTB); 2 ♂, 1 #f “ 25/ix/2009 South Africa WC// Franschhoekpas, 500m wet rock// faces beside R45 road// D.T. Bilton leg.” ( CDTB, MCZH); 1 ♀ “ South Africa WC// Tulbagh Nuwekloofpas on R44// Ca. 5 km W of Tulbagh wet rock// D.T. Bilton leg.” ( CDTB); 4 ♂, 6 ♀ “ 21/ix/2010 South Africa WC// Cederberg Uitkyk Pass above// Algeria—rockface seepages// D.T. Bilton leg.” ( CDTB, NHM, NMW, OUMNH); 1 ♂ “ 22/ix/2010 South Africa WC// madicolous seeps on// rock in Bains Kloof Pass// D.T. Bilton leg.” ( TMSA); 3 ♂ “ 24/ix/2012 South Africa WC// Cederberg madicolous seeps// at top of Uitkyk pass// D.T. Bilton leg.” ( CDTB, NHM); 1 ♂ “ 24/ix/2012 South Africa WC// Cederberg madicolous seeps// at bottom of Uitkyk pass// D.T. Bilton leg.” ( TMSA). All with red paratype labels.

Description. Size: Holotype: BL 2.05 mm; EL 1.3 mm; EW 0.75 mm. Paratypes: ♂s BL 1.95–2.1 mm; EL 1.2–1.35 mm; EW 0.7–0.8 mm. ♀s BL 2.05–2.15 mm; EL 1.25–1.35 mm; EW 0.75–0.85 mm. Dorsum ( Fig. 3 C) blackish brown with a distinct golden brassy sheen; particularly marked on pronotum elytra. Maxillary palpi dark blackish Brown; darkest at apex. Legs with femora and tarsi dark Brown; tibiae dark reddish brown. Venter predominantly dark piceous, with silvery hydrofuge pubescence.

Head: Labrum transverse, with weakly raised and thickened anterior and lateral margins, and marked apicomedian emargination, running approx. 0.3 of length. Sides of apicomedian emargination weakly raised. Surface of labrum dull, with well-marked microreticulation and stout white decumbent setae. Clypeus, frons and vertex with strong, pounctulate microreticulation throughout. Frontoclypeal suture narrow but distinct. Scattered stout, decumbent setae, particularly towards lateral margins of frons. Frons with a central elevation, broken by a small rounded 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 on clypeus. Frons and basal part of clypeus distinctly raised and thickened anterior to eyes. Decumbent white setae present on clypeus and anteriolateral edges of frons. Eyes large, occupying slightly less than 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 weakly crenulated and weakly to sharply arcuate over anterior ¾, then almost straight to rectangular posterior angles ( Fig. 3 C). Anterior margin weakly rounded, with traces of weak hyaline border in middle, which is scarcely visible. Posterior margin bisinuate to centre. Entire upper surface dull, with a wrinkled, imbricated appearance due to strong microreticulation. Coarse, shallow punctures visible in two irregular transverse rows close to posterior margin. Median longitudinal sulcus shallow, but with raised borders; foveate anteriorly and posteriorly; both foveae elongate and rather shallow, especially anterior one. Anterior and posterior admedian foveae shallow and open towards the front and sides. Adlateral foveae distinct; deep, rounded and pit-like, joined by a very shallow longitudinal furrow.

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. Explanate lateral margin present from shoulder to apex; narrow in front, rapidly widening behind shoulders and broadest close to posterior angles. Apices conjointly rounded. Each elytron 10-seriate punctate, and with two well-marked, transverse depression (saddles), one just in front of and one just behind middle, occupying intervals 1–4. Anterior saddle extending forward over intervals 4 & 5, with some traces of a keel in interval 5. Punctures of elytral striae 1–5 rather irregular, and often apparently double in front of anterior saddle. Punctures confluent and irregular in both anterior and posterior saddles. Each elytron with an additional shallow depression laterally, occupying intervals 6–7, positioned between the anterior and posterior saddles. Interval 2 strongly raised before anterior and posterior saddles. Intervals 3–4 raised between saddles and (especially in the case of interval 3) behind the posterior saddle. Intervals 5–9, outside depressions, strongly raised. Overall, the pattern of depressions and ridges creating a somewhat tuberculate appearance. Intervals 5–9, outside depressions, strongly raised throughout. Intervals with rows of short decumbent setae. Entire elytral surface finely microreticulate; microreticulation weaker than that on the pronotum; strongest on sides, weakest on raised discal intervals.

Venter: Mentum somewhat shining, with strong, isodiametric microreticulation. Submentum with weaker, more transverse microreticulation. Genae with strong isodiametric microreticulation, with raised margins to the meshes. Gular region with fine transverse microreticulation. Pronotal hypomeron with fine, isodiametric microreticulation. Prosternum finely microreticulate, with a well-marked 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, but covered in short vestiture. Median ridge splitting to form admedian ridges apically, forming an inverted Y. Border between mesoventrite and anepisternum 2 marked by a ridge, which is glabrous in front half only. Metaventrite with distinct longitudinal depression over rear 0.6 of sternite; depression of even depth—not foveate. Elytral pseudepipleurs with strong isodiametric microreticulation. Epipleurs narrow and ridge-like; microreticulate. 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 anterio-laterally. Ventrite 1 also with hydrofuge setae below hind coxae; these setae resembling those on lateral and hind margins of metaventrite. Central area of ventrites 1–5 shining, but with fine isodiametric reticulation. Ventrite 6 also microreticulate, but meshes more transverse. Ventrites 5 & 6 with transverse row of long, adpressed hair-like setae, positioned 0.75 of the way down the sternite.

Aedeagus: Elongate, with parameres attached near base, and extending well beyond apex of main piece. Main piece with truncate, asymmetrically toothed apex. Distal lobe elongate and tube-like, and extending slightly beyond apices of parameres ( Fig. 4 C).

Female: Explanate lateral margin of elytra generally somewhat narrower than in males.

Variation: Paratypes vary somewhat in the degree to which the elytral intervals are elevated, and the width of the elytral saddles; the anterior saddle extending into interval 6 in some specimens. The development of the dorsal sheen also varies, but it is present in all specimens available.

Differential diagnosis. Recognized by a combination of the entirely microreticulate dorsum, with elytra less strongly microreticulate than the pronotum, the lack of long recumbent setae on the elytral intervals, and the relatively large elytral saddles, with the anterior saddle occupying intervals 2–5, and extending forwards over intervals 4 & 5. Male genitalia also characteristic (see Fig. 4 C).

Distribution. Records run in a north-south direction, from the mountains near Franschhoek, to the Cederberg and Middelberg in the Western Cape region ( Fig. 9 ).

Etymology. Named in reference to the tuberculate appearance of the elytra.

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 6. Habitats of Pterosthetops species. A) Middelberg Pass, seepages over rock with algae on R 303 road above Blinkwater— P. hawequas, P. tuberculatus sp. nov.; B) Franschhoekpas, 500 m wet rock face formed by stream beside R 45 road— P. hawequas, P. impressus, P. tuberculatus sp. nov.; C) View along Great Escarpment from Vanrhyns Pass— P. hawequas was abundant on seep below tree at bottom left of photo. Photos D T 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.