Pterosthetops nitidus, Bilton, David T., 2016

Bilton, David T., 2016, Two new water beetles from the South African Cape (Coleoptera, Hydraenidae), Zootaxa 4137 (4), pp. 585-591 : 586-588

Pterosthetops nitidus sp. nov.

( Figs 1–3 )

Type locality. South Africa, Western Cape, False Bay, small stream on R44 road below Boskloff Peak ( Fig. 3 A).

Type material. Holotype (male): “ 3/x/2014 South Africa WC//Kogelberg – stream with seepages along R44 road// D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( ISAM).

Paratypes (16): South Africa: 10 ♂, 6 ♀ same data as holotype ( CDTB, ISAM, MCZ, NMW, OUMNH, SANC, TMSA). All with red paratype labels.

Description. Size: Holotype: BL 2.1 mm; EL 1.3 mm; EW 0.8 mm. Paratypes: ♂s BL 2.0– 2.1 mm; EL 1.25– 1.3 mm; EW 0.8 mm. ♀s BL 1.95–2.25 mm; EL 1.25–1.35 mm; EW 0.8–0.85 mm.

Colour: Dorsum ( Fig. 1 A) black, with a brassy green metallic sheen, particularly evident on elytra. Ocelli reddish brown. Maxillary palpi pitchy brown to black, legs dark reddish brown; femora darker than tibiae. Venter predominantly dark piceous, with silvery hydrofuge pubescence; pronotal hypomera and elytral pseudepipleurs paler.

Head: Labrum transverse, broadly rounded at sides and front angles, with marked, open apicomedian emargination, running approx. 0.5 of length. Surface of labrum shining, weakly microreticulate, with long, sparse, white decumbent setae over entire surface. Upper surface of head shining, with coarse, rugulose microreticulation. Clypeus with sparse decumbent setae, as on labrum. Similar setae present on centre of frons and around ocelli, but these originating at anterior margins of shallow, transverse punctures. Fronto-clypeal suture strong, arcuate. Lateral margins of frons and adjacent posterolateral area of clypeus somewhat raised. Anteocellar furrows broad, opening anterolaterally. Ocelli well-marked, shining. Frons raised in centre, and falling abruptly posteriorly, between ocelli. Compound eyes large, occupying approx. 0.4 of side of head; 15 ommatidia in longest series.

Pronotum: Distinctly cordate, with broadly and strongly explanate sides. Anterior angles obtusely rounded. Sides very weakly crenulated and weakly to sharply arcuate over anterior 0.6, then almost straight to slightly acute posterior angles. Anterior margin broadly rounded, with weak hyaline border in middle. Posterior margin strongly bisinuate to centre. Surface somewhat shining, with coarse, rugulose microreticulation. Irregular fields of sparse, coarse punctures close to anterior and posterior margins. Smaller, shallower punctures present on discal reliefs, these each bearing a long, whitish decumbent seta. Median longitudinal sulcus foveate anteriorly and posteriorly; anterior foveae somewhat elongate, posterior rounded. Anterior admedian foveae obsolete, obscured by puncture field. Posterior admedian foveae shallow, oval, orientated anterolaterally. Adlateral foveae rounded, pit-like, posterior deeper than anterior.

Elytra: Elongate oval, broadest at middle and weakly rounded at sides from base to apex. Explanate lateral margin present from shoulder to apex; narrow just behind shoulder, and broadest at middle. Apices separately rounded. Each elytron 10-seriate punctate, and with a shallow, transverse depression (saddle) just before middle, occupying intervals 2–4 and approx. 0.2 of elytral length; flat region of interval 4 extending the saddle region in front of the flat areas of intervals 2–3 by approx. same length; intervals 2–3 flat to apex behind saddle. Additional, very shallow depression posterolateral to saddle, occupying intervals 6–7. Remaining intervals raised, particularly in anterior 0.6. Punctures of elytral striae each bearing a small seta. Intervals with small, setose tubercles; setae long, white, decumbent, reaching and slightly overlapping next tubercle on interval. Entire upper surface shining, with no microreticulation visible.

Venter: Mentum shining, strongly microreticulate with sparse, golden setae; erect anteriorly, decumbent posteriorly. Submentum also shining, with traces of transverse microreticulation and scattered, coarse punctures bearing long, decumbent setae. Genae shining, with open, rugulose, isodiametric microreticulation in foveae and transverse microreticulation towards posterior margins. Gula shining, with transverse microreticulation.

Prosternum dull, finely wrinkled, with dense hydrofuge vestiture. Weak, glabrous central ridge visible in posterior 0.4. Pronotal hypomeron broad, shining, with rugulose isodiametric microreticulation and scattered golden decumbent setae. Meso and metaventrite cloathed in dense hydrofuge vestiture. Median ridge of mesoventral plaques forming an inverted Y; stem and arms of equal length; weaker admedian and lateral ridges also visible. Metaventrite with distinct longitudinal depression over rear 0.5 of sternite; foveate in centre. Elytral pseudepipleurs with weak microreticulation; shining. Epipleurs narrow and ridge-like; shining. Abdominal ventrites 1–4 fringed with long, closely-set squamiform setae at hind margins. Ventrite 1 with narrow band of hydrofuge vestiture along anterior margin, extending to the posterior in a triangular patch laterally. Ventrites 2–5 with traces of hydrofuge vestiture laterally. Ventrites 1–6 shining, with open, transverse microreticulation; more transverse on ventrite 6 than preceding ventrites. Ventrites 5–6 with irregular transverse row of fine punctures approx. 0.3 from posterior margin; punctures bearing long, decumbent setae.

Aedeagus: Elongate, with parameres attached near base, and extending well beyond apex of main piece. Main piece with small, but distinct tooth in ventral view, and stout ventral setae. Distal lobe elongate and tube-like; almost straight, and extending just beyond apices of parameres ( Fig. 2 A).

Female: Microreticulation of head and pronotum stronger than that of males; elytra more explanate at lateral margins; venter with stronger microreticulation throughout; abdominal ventrites dull.

Variation: Elytral sheen varies amongst paratypes, sometimes being almost absent.

Differential diagnosis. This new species would key to P. uitkyki Bilton, 2014 using the key in Bilton (2014) due to its shining elytra which lack evident microreticulation and the single, relatively long elytral saddle which does not extend onto interval 1. It is readily distinguished by its smaller size (1.95–2.25 mm vs. 2.25–2.65 mm) the stronger microreticulation on the abdominal ventrites, and the very different aedeagus (see Fig. 2 A), which is closer to that of Pterosthetops tuberculatus Bilton, 2014 , differing from this species in particular by the much narrower apex of the main piece (see Fig. 4C in Bilton 2014).

Distribution and ecology. Known to date only from the type locality, a madicolous seepage over rock beside a small stream flowing into False Bay, in the Western Cape close to Gordon’s Bay ( Fig. 3 A).

Etymology. Named in reference to the shining dorsal surface. The specific epithet is a noun in the genitive case.

Figures

FIGURE 1. Dorsal habitus of A) Pterosthetops nitidus sp. nov.; B) Oomtelecopon namaqum sp. nov. Scale bars = 1 mm.

FIGURE 2. Aedeagus of A) Pterosthetops nitidus sp. nov.; B) Oomtelecopon namaqum sp. nov. Scale bar = 0.5 mm.

FIGURE 3. Type localities of A) Pterosthetops nitidus sp. nov. — South Africa, Western Cape, small stream on R 44 road below Boskloff Peak, specimens collected from shaded wet rock faces at the right-hand side of the stream; B) Oomtelecopon namaqum sp. nov. — South Africa, Northern Cape, Kamiesberg, stream in Langkloof ca. 15 km NE of Garies, 1,000 m, specimen splashed from mossy area on bank below tree. Photos D. T. Bilton.