Pterosthetops coriaceus, 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 : 439-443

publication ID	https://doi.org/ 10.11646/zootaxa.3811.4.2
publication LSID	lsid:zoobank.org:pub:99629EFB-F2F6-4DE8-AABA-D71069106912
DOI	https://doi.org/10.5281/zenodo.6129813
persistent identifier	https://treatment.plazi.org/id/03D687DB-E35A-0C12-BBB9-8E90FA7F9F08
treatment provided by	Plazi
scientific name	Pterosthetops coriaceus
status	sp. nov.

Treatment

Pterosthetops coriaceus View in CoL sp. nov.

( Figs 1 View FIGURE 1 A & 2A)

Type locality. South Africa, Western Cape, Cederberg mountains, seepages over exposed sloping rock beside stream @ 1,200 m below Wolfberg Arch, beside Matjiesrivier-Wupperthal road, D.T. Bilton leg. ( Fig. 5 View FIGURE 5 A).

Type material. Holotype (male): “ 23/ix/2011 South Africa WC// Cederberg—stream with seeps// over rock @ 1,200 m below// Wolfberg Arch D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( SAM).

Paratypes (9): South Africa: 4 ♂, 5 ♀ “ 23/ix/2011 South Africa WC// Cederberg—stream with seeps// over rock @ 1,200 m below// Wolfberg Arch D T Bilton leg.” ( CDTB, NMW, SANC, TMSA). All with red paratype labels.

Description. Size: Holotype: BL 2.15 mm; EL 1.4 mm; EW 0.8 mm. Paratypes: ♂s BL 2.15–2.2 mm; EL 1.4–1.45 mm; EW 0.8–0.85 mm. ♀s BL 2.2–2.25 mm; EL 1.4–1.55 mm; EW 0.8–0.85 mm. Dorsum ( Fig. 1 View FIGURE 1 A) dark brown to black with a weak golden sheen, particularly around elytral margins and on head and pronotum. Maxillary palpi pitchy to black, legs pitchy to black, with tibiae somewhat lighter. Venter predominantly dark piceous, with silvery hydrofuge pubescence.

Head: Labrum transverse, rounder apicolaterally, with marked apicomedian emargination, running approx. 0.3 of length. Sides of apicomedian emargination distinctly raised. Surface of labrum dull, with strong microreticulation and short, white decumbent setae around apical and lateral margins. Entire upper surface of head dull, with strong microreticulation. Scattered white decumbent setae present, especially close to lateral margins of clypeus. Fronto-clypeal suture weak but visible; stronger laterally. Frons with a central elevation, broken by a 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 onto frons. Lateral margins of frons and basolateral areas of clypeus thickened, ridged beside and in front of arcuate sulci. 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 coarsely crenulated and weakly to sharply arcuate over anterior 2/3, then almost straight to slightly acutely rounded posterior angles ( Fig. 1 View FIGURE 1 A). Anterior margin weakly bisinuate, with very narrow hyaline border in middle, which is scarcely visible. Posterior margin weakly bisinuate to centre. Entire upper surface dull, with strong microreticulation, except on parts of pronotal reliefs where it is reduced to small punctulae. Median longitudinal sulcus foveate anteriorly and posteriorly; both foveae elongate, anterior fovea running for approx ½ of pronotal disc, posterior one for approx 1/3. Sides of sulcus bordered by ridges where reticulation is weak. Anterior and posterior admedian fovea shallow and open, with long decumbent white setae; setal sockets with anterior rim raised slightly. Adlateral fovea deeper, rounded and pit-like, particularly posteriorly, and joined by a weakly marked, shallow longitudinal channel.

Elytra: Elongate and broadest at middle. Weakly rounded at sides from shoulder to apex. Explanate lateral margin present from shoulder to apex; widest towards apex. Apices separately rounded. Each elytron 10-seriate punctate and with two transverse depressions (saddles), one just before middle, occupying intervals 2–5, the second midway between first and apex, occupying intervals 2–4. Additional, shallow depressions present between second saddle and apex, occupying intervals 2–3, and between the two saddles, occupying intervals 5–8; deepest in intervals 6 & 7. Punctures of elytral striae each bearing a small seta. Puncture rows becoming slightly irregular in anterior saddle; random in posterior saddle, with series 2 & 3 ending in the depression between posterior saddle and apex. Intervals raised to varying degrees. Interval 1 raised along suture, particularly behind the middle. Interval 2 slightly raised in front of anterior saddle and between anterior and posterior saddles. Intervals 3 & 4 strongly raised into broad ridges, with relatively weak microsculpture, both in front of anterior saddle and between in and the posterior one. Interval 4 also raised in this manner behind posterior saddle. Interval 6 raised for some distance outside anterior saddle, then flat in region between anterior and posterior saddles, then elevated posteriorly. Interval 7 with elongate raised area adjacent to median saddle. Raised portions of elytra, and saddles, giving a somewhat tuberculate appearance. Elytal intervals with short, scattered setae. Elytral dorsal surface predominantly dull and microreticulate; less so on ridges of internal intervals, where microreticulation is weakest.

Venter: Mentum, submentum, genae and gular region shining but strongly microreticulate, giving a coriaceous appearance. Only gular suture visible. Long, golden setae present in anteriolateral areas of mentum and smaller decumbent setae on its lateral margins. Prosternum with a broad central ridge, flanked by two semicircular depressions. Surface finely reticulate and with dense hydrofuge vestiture. Pronotal hypomeron broad, with isodiametric microreticulation and sparse, long setae just outside hypomeral carinae. Meso and metaventrites with dense hydrofuge vestiture; vestiture shorter and less dense towards lateral and hind margins. Mesoventral plaques distinct, glabrous. Median ridge splitting to form admedian ridges apically, forming an inverted Y. Border between mesoventrite and anepisternum 2 marked by a broad glabrous ridge. Metaventrite with a well-marked longitudinal depression over posterior 0.75 of sternite, with a narrow median ridge anterior to this, extending to the hind border of the mesoventrite, between mesocoxae. Elytral pseudepipleurs broad and shallowly concave; strongly microreticulate. Epipleurs narrow and ridge like; microreticulate. Abdominal ventrites 1–4 fringed with long, closely-set squamiform setae at hind margins. Abdominal ventrites 1–4 entirely covered with hydrofuge vestiture, which is denser towards anterior margins and in triangular anteriolateral patches. 5th ventrite also with hydrofuge vestiture, except for the posterior 1/5, which is glabrous and microreticulate. Entire surface of ventrite 6 also glabrous and microreticulate. Ventrites 5 & 6 with transverse row of sparse, long, adpressed hair-like setae, positioned 0.8 of the way down the sternite.

Aedeagus: Strongly elongate, with parameres attaching close to base and extending beyond the apex of the main piece. Main piece with asymmetrical apical tooth, and long, curved, tube-like distal lobe, extending well beyond the paramere apices. ( Fig. 2 View FIGURE 2 A).

Female: Mesoventral plaques weaker than in males, otherwise without significant differences from males.

Variation: Paratypes vary somewhat in the development of the golden sheen on the dorsal surface. Some appear distinctly golden; others almost matt black. There is also some variation in the depth of elytral puncture rows, and the height of intervals. Raised intervals also vary in their degree of microreticulation—from weak to strong.

Differential diagnosis. Recognized by a combination of the very strongly microreticulate dorsum (including elytra), the lack of long recumbent setae on the elytral intervals, and the two weak elytral saddles, both restricted to intervals 2–4. Male genitalia also highly characteristic (see Fig. 2 View FIGURE 2 A).

Distribution. Known to date only the type locality, seepages on a sloping rock platform beside a stream in the southeastern part of the Cederberg range, in an area transitional between fynbos and succulent karoo biomes ( Fig. 9 View FIGURE 9 ). Etymology. Named in reference to the wrinkled appearance of the dorsal surface and some parts of the venter.