Mesoceration hirsutum, Bilton, David T., 2015

Bilton, David T., 2015, New species and new records of Mesoceration Janssens, 1967 from South Africa (Coleoptera, Hydraenidae), Zootaxa 3972 (4), pp. 495-520 : 503-504

Mesoceration hirsutum sp. nov.

( Figs 1 , 2 & 5 )

Type locality. South Africa, Western Cape, Cederberg, Breëwaterkloof stream, ca. 2 km SE of Uitkyk Pass, 1,050m ( Fig. 5 C).

Type material. Holotype (male): “ 23/ix/2014 South Africa WC// Cederberg stream ca. 2 km // SE of Uitkyk Pass 1,050 m // D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( SAM).

Description. Size: Holotype: BL 1.8 mm; EL 1.05 mm; EW 0.65 mm.

Colour: dorsum ( Fig. 1 D) black, with golden-yellow setae on pronotum and elytra; ocelli dark reddish brown. Legs dark reddish brown. Maxillary palpi pitchy. Venter dark pitchy brown to black; elytral pseudepipleurs paler in posterior 0.5. Much of ventral surface of thorax and abdomen silvery due to hydrofuge vestiture.

Head: Labrum slightly transverse, strongly rounded apicolaterally, with apicomedian emargination over 0.5 of length. Sides of apicomedian emargination and anterior angles weakly raised. Surface shining, with weak, obsolete microreticulation and sparse punctures, each bearing a fine decumbent seta. Frontoclypeal suture obsolete, weak, arcuate. Clypeus shining, finely wrinkled, with sparse punctures bearing fine, decumbent setae. Frons and vertex shining, coarsely and confluently punctate; punctures bearing short, recumbent, golden-yellow setae. Anteocellar sulci broad, shallow, open laterally; sulci and areas between sulci and compound eyes sculptured as central frons. Ocelli small, shining. Compound eyes relatively large, occupying approx. 0.5 lateral margin of head, 16 ommatidia in longest series.

Pronotum: Cordate, somewhat transverse, broadest at middle. Anterior margin arcuate over central 0.5, without hyaline border; posterior margin weakly rounded. Anterior angles obtusely rounded; posterior angles obtuse. Lateral margins sinuated from widest point to base; broadly marginated and strongly crenulated in anterior 0.5, weakly crenulated in posterior 0.5. Discal reliefs and posterior 0.5 of lateral explanate areas coarsely and confluently punctate; punctures bearing long, golden-yellow, recumbent setae. Explanate lateral margins shining, impunctate in anterior 0.5. Microreticulation restricted to narrow band of transverse meshes close to anterior margin. With 10 distinct foveae as follows: Anterior median fovea elongate, shallow and punctate over anterior 0.5, deeper and impunctate, smooth behind; posterior median fovea circular, deep and impunctate, shining. Anterior admedian fovea shallow, transverse oval, punctate; posterior admedian fovea shallow, elongate oval, orientated anterolaterally, punctate, punctures shallower than on reliefs, traces of microreticulation. Anterior adlateral fovea elongate, oval, open laterally, shining and impunctate; posterior adlateral fovea small, deep, circular.

Elytra: Elongate oval, broadest behind middle. Sides rounded; gradually attenuated to shoulders and apex. Apicolateral angles obsolete, apices conjointly rounded to suture. Sides narrowly explanate, entire. Punctures of elytral series evident to apex; larger in anterior 0.5, smaller behind. Discal series striate impressed. Series 1 and 2 confluent behind posterior declivity. Series 5 and 6 confluent in anterior 0.3. Serial punctures with long, recumbent, golden-yellow setae, reaching next puncture in row. Intervals 2–3 transversely rounded; outer ones flat. Intervals coarsely granulate, granules bearing recumbent setae similar to those in elytral series. Interval 8 carinate to approx. 0.1 from apex.

Legs: Apical protarsomere with two stout ventral setae; basal three protarsomeres with suction setae.

Venter: Mentum shining, with rugulose isodiametric microreticulation; smooth and lacking microreticulation in centre close to posterior margin. Elongate, white, erect setae close to anterior margin of mentum and on palpifer. Submentum smooth and shining, finely wrinkled behind, with scattered punctures bearing white, recumbent setae. Genae shining, with fine transverse wrinkles. Gula smooth and shining anteriorly, with fine, transverse microreticulation posteriorly. Prosternum with well-marked central ridge, somewhat thickened in posterior 0.5; with broad, shallow depression either side of centre, reaching to above outer angles of procoxae. Surface rugulose, with dense hydrofuge vestiture. Pronotal hypomeron smooth and shining, with deep, circular depression at level of anterior edge of procoxae. Mesoventrite and metaventrite with dense hydrofuge vestiture. Mesoventral plaques glabrous, forming inverted Y, stem 0.5 length of arms. Apex of arms connecting with ridges along posterior median projection of mesoventrite, to form trapezoidal ridge. Admedian and adlateral ridges present, but under hydrofuge vestiture. Metaventrite with broad, elongate, median fovea over posterior 0.6 and small semicircular glabrous patch posteromedially. Anteromedial margin of metaventrite with M-shaped longitudinal ridge, pits present inside and outside arms of M, below mesocoxae. Elytral pseudepipleurs broad, shining, attenuated to apex over posterior 0.3; elytral epipleurs narrow, ridge-like. Abdominal ventrites 1–4 with dense hydrofuge vestiture. Abdominal ventrite 5 with broad, semicircular, shining, glabrous patch occupying posterior 0.5. Junction between pilose and glabrous areas marked by irregular row of fine, decumbent setae. Similar row halfway down glabrous patch. Abdominal ventrite 6 glabrous, shining, traces of transverse microreticulation. Row of setae close to apex, sparser than those on ventrite 5.

Aedeagus: Relatively large, highly elongate, straight in ventral view, with parameres attaching close to base and extending beyond the apex of the main piece. Main piece with strong, stout apical tooth on left side, tooth overhanging base of distal lobe. Distal lobe elongate, extending well beyond paramere apices; apex expanded ( Fig. 2 D).

Female: Unknown.

Differential diagnosis. A rather isolated species morphologically. Would key to the rivulare group in Perkins & Balfour-Browne (1994) on account of the carinate 8th elytral interval, 5th and 6th elytral series confluent anteriorly, and the apparent lack of microreticulation on the pronotal reliefs. This apparent lack of microreticulation is, however, a result of the coarse confluent punctation of the reliefs, and this species does not actually appear to belong to the rivulare group, whose species are otherwise very different in both external and aedeagal anatomy (see Perkins & Balfour-Browne 1994; Perkins 2008). Instead, the new species seems to belong to the endroedyi group sensu Perkins & Balfour-Browne (1994), some of whose members it more closely resembles in having granulate elytral intervals and a coarsely punctate pronotum. Discal pronotal microreticulation, is also actually present in M. hirsutum sp. nov., but only visible in some of the fovea. The aedeagus of the new species most closely resembles M. piceum Perkins, 2008 , a species with which the new taxon was sympatric in the Cederberg. M. hirsutum sp. nov. differs from M. piceum in the much more strongly punctate pronotum, the more strongly granulate elytral intervals, as well as the presence of golden-yellow decumbent setae on the pronotum and elytra, the larger size (1.8 mm vs. 1.53 mm), and details of the aedeagus, which is larger, has a stronger lateral tooth on the main piece, and a much straighter distal lobe in the new species.

Distribution. To date known only from the type locality ( Fig. 5 C), a high-altitude east facing stream flowing through Cederberg Sandstone Fynbos (sensu Mucinia & Rutherford 2006) in Breëwaterkloof, at the head of the Matjies River in the Cederberg range. The only known specimen was collected under a boulder in a riffle. Other beetles found in the same stream included Mesoceration dissonum Perkins & Balfour-Browne, 1994 , M. granulovestum Perkins, 2008 , M. jucundum Perkins & Balfour-Browne, 1994, M. languidum Perkins & Balfour- Browne, 1994, M. periscopum Perkins, 2008 , M. piceum , M. repandum Perkins, 2008 and M. rivulare Perkins & Balfour-Browne, 1994 —this apparently being the largest number of co-occurring species of the genus so far reported.

Etymology. Named in reference to the stiff golden-yellow hairs on the pronotum and elytra.

Figures

FIGURE 1. Habitus of Mesoceration holotypes. A) M. caniplenum sp. nov.; B) M. foggoi sp. nov.; C) M. helmei sp. nov.; D) M. hirsutum sp. nov.

FIGURE 2. Aedeagi of Mesoceration species. A) M. caniplenum sp. nov., holotype; B) M. foggoi sp. nov., holotype; C) M. helmei sp. nov., holotype; D) M. hirsutum sp. nov., paratype. Scale bar = 0.25 mm.

FIGURE 5. Habitats of Mesoceration species in South Africa. A) KwaZulu-Natal, uKhahlamba Drakensberg National Park, Injisuthi, stream in Afromontane forest remnant below Van Heyningen’s Pass— M. caniplenum sp. nov., beetles collected from the wet rockface on the right hand side of the stream; B) Western Cape, Matsikammaberg, stream 1 km NW of Sewefontein farm— M. foggoi sp. nov., M. umbrosum; C) Western Cape, Cederberg, Breëwaterkloof stream, ca. 2 km SE of Uitkyk Pass, 1,050 m— M. hirsutum sp. nov., M. dissonum, M. granulovestum, M. jucundum, M. languidum, M. periscopum, M. piceum, M. repandum, M. rivulare; D) Western Cape, Franschhoek Pass, wet rock faces beside stream crossing R 45 road, 500 m— M. rugulosum sp. nov. Photos D. T. Bilton.