Parhydraena cataracta, Bilton, 2018

Bilton, David T., 2018, A new humicolous Parhydraena d’Orchymont, 1937 from South Africa (Coleoptera, Hydraenidae), Zootaxa 4378 (2), pp. 284-288 : 285-287

Parhydraena cataracta sp. nov. ( Figs 1–2 )

Type locality. South Africa, Western Cape, Hex River Mountains, ca. 2 km W of Waaihoek peak, Green Gulley on SE slopes of Mostertshoek Twins , wet boulder scree beside stream below waterfall, 33° 28’ 20.86’’S 19° 17’ 14.61’’E, 1,320 m ( Fig. 2 ).

Type material. Holotype (male): “ 14/ii/2017 South Africa WC// Hexrivierberge, Green Gulley// 1,320 m, Mostertshoek Twins// wet boulders by stream D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( AMG).

Paratypes 10 ♀ same data as holotype ( AMG, CDTB, ISAM, NMW, SANC) . All with red paratype labels.

Description. Size: Holotype: BL 1.75 mm; EL 1.1 mm; EW 0.8 mm. Paratypes: BL 1.95–2.15 mm; EL 1.25–1.3 mm; EW 0.85–0.95 mm.

Colouration: Dorsum ( Fig. 1A ) head dark reddish brown to black; centre of vertex and frons and entire labrum blackish, sides of vertex, ocelli and frons paler. Pronotum and elytra pale reddish brown. Legs pale reddish brown; tarsi and maxillary palpi yellow. Antennal stem yellow, club blackish brown. Venter pale reddish brown; darkest in centre and paler towards margins.

Head: Labrum transverse, equal in length to clypeus, rounder apicolaterally, with broad, open, shallow apicomedian emargination, running approximately 0.4 of length and broadly rounded lateral lobes. Surface weakly shining, with isodiametric microreticulation and fine, sparse punctures bearing whitish recumbent to decumbent setae. Anterior and lateral margins with long, yellowish arcuate setae, densest along anterior margins close to apicomedian emargination. Frons weakly shining, microreticulate and punctate as labrum; microreticulation strongest close to compound eyes and towards hind margin. Fronto-clypeal suture strong, well impressed. Clypeus punctured as frons and labrum, microreticulation less strongly impressed, surface more shining. Ocelli small, indistinct, situated close to the base of a narrow, arcuate, groove-like longitudinal interocular fovea. Compound eyes relatively small, occupying approximately 1/3 lateral margin of head, 7 ommatidia in longest series when viewed dorsally. Maxillary palpi short, elongate, approximately 0.4 width of head; ratio of meres 2–4 approximately 4/2/9.

Pronotum: Broad, cordate, transverse; anterior margin straight, with very shallow emargination over median third, where there is a trace of a narrow hyaline border. Anterior angles obtusely rounded. Sides rounded, with broad, shallow crenulations; broadest just in front of middle, gradually narrowing and slightly sinuate to obtuse posterior angles. Posterior margin weakly bisinuate around centre. Discal reliefs shallow, with moderate to dense U-shaped punctures, each with centre of anterior margin extended posteriorly as a narrow, shining ridge, devoid of microreticulation, almost dividing the puncture in two. Relief cuticle between punctures weakly shining, with shallow, effaced, isodiametric microreticulation. Impressions shallow; anterior V-shaped, broadly open anteriorly, connecting laterally with anterolateral impression. Posterior impression broadly U-shaped. Lateral impressions broad, very shallow, opening to anterior or posterior angles. Cuticle of impressions dull, with strong, rugulose, isodiametric microreticulation. Punctures in impressions obsolete, only shining longitudinal ridges evident, contrasting with microreticulate background and 2– 4x length of ridges of relief punctures.

Elytra: Elongate oval, broadest at middle, attenuated posteriorly to truncately rounded apex. Lateral margins strongly explanate from just behind shoulder to apical 0.2; minutely serrate. Ten-seriate punctate, punctures becoming shallower behind posterior declivity. Punctures of series spaced 0.7–2.5 puncture widths apart; each puncture granulate anteriorly, granules bearing short, stiff recumbent to decumbent setae, reaching just beyond posterior margin of puncture. Intervals dull, finely microreticulate, 1.5– 2x as wide as serial punctures, with unilinear row of small, shining granules, each bearing a long, white recumbent to decumbent seta, reaching next granule in row. Granules approximately 1.2– 2x diameter of those in punctures of elytral series.

Venter: Mentum, submentum and genae dull. Mentum strongly microreticulate and densely punctate, punctures bearing long, yellowish, recumbent to erect setae. Submentum, genae and gula as mentum, but with small, scattered, shining longitudinal ridges. Prosternum dull, microreticulate and punctate, with dense hydrofuge vestiture. Pronotal hypomeron broad, dull, with strong, isodiametric microreticulation, mesh diameter approximately equal to that of a single ommatidium. Wet hypomeron glabrous; bubble hypomeron with sparse, short setae. Meso- and metaventrites strongly microreticulate, punctate, with hydrofuge vestiture. Basal 0.5 of metaventrite with strong longitudinal carina; apical 0.5 with shallow, elongate-oval median fovea, deepest anteriorly. Elytral pseudepipleurs broad, flat, shining, narrowed approximately 0.2 from base; with short, stiff bristle basally, otherwise glabrous. Epipleurs narrow, ridge-like. Abdominal ventrites 1–4 strongly microreticulate, punctate; covered in hydrofuge vestiture; ventrite 5 with same vestiture in narrow band along anterior margin. Remainder of ventrite 5 and ventrite 6 glabrous, weakly shining, with open, isodiametric microreticulation. Irregular transverse row of medium punctures bearing decumbent setae approximately 1/3 from apex of ventrite. Last ventrite asymmetrical, apex with short elongate lobe and stout setae; last tergite with short setae on either side of narrow apicomedian notch into which fits lobe of last ventrite.

Legs: Relatively short, basal 3 pro- and mesotarsomeres with pads of suction setae.

Aedeagus: Main piece strongly arcuate in lateral view; widest at trilobed apex. Gonopore tube small, weakly chitinized, elongate and tube-like, broadest at base and rapidly tapering to fine point. Distal piece elongate, arcuate, spine-like. Parameres relatively thin; left shorter than right ( Fig. 1B ).

Female: Elytral apices more strongly acuminated and less truncate than males; lateral margins of elytra slightly more broadly explanate ( Fig. 1B ). Last ventrite elongate, with bluntly pointed apex, weakly microreticulate, scattered, long, whitish recumbent setae in apical half. Last tergite slightly elongate, broadly rounded apex, sparsely punctate, punctures bearing short, stiff, recumbent to erect setae; apical margin with short, dense, peg-like setae. Tarsi without suction setae.

Variation: Paratypes vary somewhat in colouration and in the intensity of the dorsal reticulation, particularly on the pronotum. In some instances the head is paler than the holotype, in others the pronotum and elytra darker, but in all specimens (except tenerals) the head is darker in colour than the pronotum and elytra.

Differential diagnosis. Parhydraena cataracta sp. nov. would key to P. toro in Perkins (2009) , resembling this species in both external and aedeagal morphology. It differs from P. toro in the paler colouration, with the head darker than the pronotum and elytra, the shallower pronotal impressions with less evident punctation, the presence of shining longitudinal ridges (remnants of punctures) over the majority of the pronotal disc (such sculpture is restricted to margins in P. toro ), the stronger elytral interval granules and on details of the aedeagus, particularly the longer distal lobe, which surpasses the apex of the main piece ( Fig. 1C ).

Distribution and habitat. To date only known from the type locality ( Fig. 2 ), a cool, shaded, south-facing gulley (known locally as Green Gulley) on the SE slopes of Mostertshoek Twins in the Hex River Mountains, Western Cape Province. Here P. cataracta sp. nov. was flushed from boulders and gravels beside a small stream immediately below a vertical rockface. The occupied microhabitat was kept moist by spray/mist from the falls, even at the height of summer when the specimens were collected. P. cataracta sp. nov. occurred together with Discozantaena cf. karoo Perkins, 2005.

Etymology. Named in reference to the habitat, from the Latin cataracta (= waterfall). The specific epithet is a noun in apposition.

Figures

FIGURE 1. Parhydraena cataracta sp. nov. A) male holotype habitus; B) female paratype habitus; C) Aedeagus, ventral and lateral views.Scalebar (A & B) = 1 mm;(C) = 100 µm.

FIGURE 2. Parhydraena cataracta sp. nov. type locality, South Africa, Western Cape, Hex River Mountains, Green Gulley on SE slopes of Mostertshoek Twins. A) overview of Green Gulley, location of area occupied below arrow; B) wet boulder/gravel scree belowwaterfall where specimens werecollected.