Discozantaena occidentalis, Bilton, David T & Perkins, Philip D, 2012

Bilton, David T & Perkins, Philip D, 2012, Two new species of Parhydraenini from South Africa (Coleoptera: Hydraenidae), Zootaxa 3342, pp. 51-59 : 52-53

Discozantaena occidentalis , new species

( Figs. 1 & 2 )

Type Material. Holotype (male): 1/x/2008, South Africa, Western Cape Province, West Coast National Park, permanent pond at Abrahamskraal, 33° 13’ 58.89” S, 18° 08’ 10.72” E, 3 m, D.T. Bilton leg. ( SAM). Paratypes (17): 2/x/2010, South Africa, Western Cape Province, West Coast National Park, Abrahamskraal, permanent waterhole with Juncus and reeds, D.T. Bilton leg. (2 SAM, 2 TMSA, 2NHM, 2 NMW, 2 MCZ, 7CBP).

Differential Diagnosis. Members of this species will key to D. genuvela in Perkins (2005). The two species differ in body shape and colour. D. genuvela is more broadly explanate (head, pronotum and elytra); the explanate margins of the elytra nearly attain the apices, and all explanate margins are usually much lighter in colour than the remainder of the dorsum. In D. occidentalis n. sp. the explanate elytral margins end well before the apices, the apices therefore appearing more accuminate, and there is less contrast in the colours of the margins and the remainder of the dorsum. In D. genuvela the pronotum is more transverse and less arcuate laterally, and the elytra are longer relative to the pronotal length (ca. 1.13/ 0.39 in D. genuvela ; 1.04/ 0.44 in D. occidentalis n. sp.). The male genitalia of the two species are similar in that both have a corkscrew-like flagellum. The aedeagus of D. occidentalis n. sp. differs diagnostically from that of D. genuvela , however, being much shorter and having a much wider mainpiece, especially apically ( Fig. 2 ).

Description. Size: (length/width, mm) holotype: body (length to elytral apices) 1.64/0.84, head 0.26/0.50, pronotum 0.44/0.69, elytra 1.04/0.84. Colour: Dorsum dark brown to piceous, with margins of pronotum, frontal angles of head and reflexed margins of elytra paler. Ventral surface piceous, elytral epipleurs and pronotal hypomera brown. Head: Frons relatively flat between oblique lateral fovea, disc shiny, weakly granulate; decumbent hyaline setae sparse and relatively long, directed largely posteriorly on disc, and centrally towards eyes. Clypeus transverse, weakly emarginated, with rounded anterior angles; smooth and shining in centre; rugose towards sides. Labrum shining and sparsely setose; apicomedian emargination strongly reflexed into a broadly elevated conical projection. Pronotum: Strongly transverse; anterior margin weakly arcuate, median ½ with narrow hyaline border; anterior angles sharply rounded; sides arcuate then emarginated before tooth-like posterior angles. Sides minutely denticulate; denticles with small, hyaline setae. Pronotal disc shining, with well-marked anterior and posterior broad U-shaped impressions. Pronotum with relatively fine and sparse, hyaline decumbent setae, each arising from a linearly elongate, backwardly-pointing granule; setae denser in depressions, sparser in explanate areas towards lateral margins. Hind margin with central 1/3 slightly raised, shiny and with sparse setae. Wings full-length. Elytra: Anterior angles sharply rounded, arcuate to just behind middle, then attenuate to narrowly truncate apices. Lateral margin narrowly explanate midway to interval outside tenth puncture series. Ten seriate punctate, with two additional, weakly differentiated series on explanate margins. Punctures of series transversely oval; shallow and relatively open towards hind margins, front margins steeper. Each puncture overhung by small granule, bearing a fine, backwardly-pointing decumbent hyaline seta; each seta reaching back as far as next granule in series. Punctures broader towards elytral base. Intervals lacking punctures or microreticulation; shining. Sutural margin raised in posterior 2/3. Venter: Metaventrite with weak median longitudinal impression. Thoracic sterna and abdominal ventrites 1–4 entirely and 5 basally clothed with sparse pubescence; longer setae present towards hind margins of metaventrite and abdominal ventrites. Aedeagus: Total length 0.44 mm; mainpiece length 0.28 mm; mainpiece short and stout, with characteristically shaped widened distal area. Flagellum short, stiff, with a corkscrew-like single coil. Female: Labrum lacking apicomedial conical projection. Pronotal impressions slightly deeper than in males. Median longitudinal impression of metaventrite deeper and more linear than in males. Variation: Paratypes vary slightly in overall shape, some having more broadly rounded elytral angles than observed in the holotype. Such variation is present in both sexes.

Etymology. Named in reference to the distribution on the west coast of the Western Cape Province of South Africa.

Distribution and Ecology. Currently known only from the type locality, Abrahamskraal ( Fig. 5 ), a permanent man-made waterhole north of Yzerfontein in West Coast National Park, Western Cape Province. At Abrahamskraal beetles were found living in damp marginal plant litter overlying silt, on limestone rock. Occupied areas had sparse algal biofilms, and were mostly shaded by spike-rush tussocks ( Juncus cf. krausii), which maintained a humid microenvironment. Beetles were collected by shore washing, or by scraping off surface debris by hand, and agitating this in shallow water until specimens floated to the surface. Abrahamskraal contains a rich water beetle fauna, with a range of Cape endemic species, particularly Dytiscidae , including Rhantus cicurus (Fabricius, 1787) , Coelhydrus brevicollis Sharp, 1882 , Darwinhydrus solidus Sharp, 1882 and Primospes suturalis Sharp, 1882 . Discozantaena occidentalis n. sp. was microsympatric with Ochthebius extremus Péringuey, 1892 and Ochthebius granulinus Perkins, 2011 .

Figures

FIGURE 1. Discozantaena occidentalis n. sp., dorsal and lateral habitus of holotype.

FIGURE 2. Discozantaena occidentalis n. sp., aedeagus of holotype.

FIGURE 5. Type Locality of Discozantaena occidentalis n. sp. Abrahamskraal, West Coast National Park, Western Cape Province, South Africa. Discozantaena found at far end of site, beneath spike-rush tussocks. Photo P. Cotton.