Mesoceration caniplenum, 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 : 496-497

Mesoceration caniplenum sp. nov.

( Figs 1 , 2 & 5 )

Type locality. South Africa, KwaZulu-Natal, uKhahlamba Drakensberg National Park, Injisuthi, stream in Afromontane forest remnant below Van Heyningen’s Pass ( Fig. 5 A).

Type material. Holotype (male): “ 27/xii/2013 South Africa KZN// Ukhahlamba Drakensberg NP// 1st stream below Van Heyningen’s//Pass @ Injisuthi D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( SAM).

Paratypes (14): South Africa: 6 ♂ same data as holotype; 6 ♂, 2♀ “ 27/xii/2013 South Africa KZN// Ukhahlamba Drakensberg NP// 2nd stream below Van Heyningen’s//Pass @ Injisuthi D T Bilton leg.” ( CDTB, MCZ, NMW, SAM, SANC, TMSA). All with red paratype labels.

Description. Size: Holotype: BL 1.6 mm; EL 0.9 mm; EW 0.6 mm. Paratypes: ♂s BL 1.45–1.75 mm; EL 0.85–1.0 mm; EW 0.55–0.65 mm. ♀s BL 1.6–1.65 mm; EL 0.85–0.9 mm; EW 0.6–0.65 mm.

Colour: Dorsum ( Fig. 1 A) with head dark pitchy brown to black; ocelli, anteocellar sulci and area between sulci and compound eyes paler. Pronotum reddish brown on disc, broadly yellow towards lateral margins. Elytra yellow; suture, lateral margins and serial punctures darker. Legs pale yellow, maxillary palpi pale yellow with last segment infuscated over most of length. Venter with head, pronotum and elytral pseudepipleurs yellow; meso and metaventrites, abdominal ventrites and elytral epipleurs reddish brown. Prosternum, meso- and metaventrites, and much of abdomen silvery due to hydrofuge vestiture.

Head: Labrum quadrate, markedly broader anteriorly than posteriorly. Rounded apicolaterally with broad apicomedian emargination occupying approx. 0.5 of length. Sides of apicomedian emargination and apicolateral angles weakly raised. Surface shining, with fine, elongate microreticulation, obsolete on centre at base. Scattered fine punctures with short, fine, decumbent setae. Frontoclypeal suture strong, arcuate. Clypeus strongly shining, with scattered medium punctures bearing fine, decumbent setae, and traces of microreticulation lines laterally. Centre of frons and vertex shining; punctation and setation as clypeus, microreticulation absent. Anteocellar sulci shallow, dull, punctate and microreticulate; same sculpture between sulci and lateral margins of compound eyes. Ocelli large, flat, shining. Compound eyes moderate, occupying approx. 0.35 lateral margin of head, 12 ommatidia in longest series.

Pronotum: Cordate, transverse, broadest at middle. Anterior margin arcuate over median 0.6, without hyaline border; posterior margin straight. Anterior angles broadly rounded, posterior angles rectangular. Lateral margins sinuated from widest point to base; narrowly marginated and weakly crenulate. Disc relatively flat, shining, with band of transverse microreticulation over central 0.5 close to anterior margin, and partly obsolete isodiametric meshes in foveae, laterally and on parts of pronotal reliefs. Microreticulation absent from central reliefs. Pronotum with sparse, fine, shallow punctures, bearing long, fine, decumbent setae on explanate lateral margins. With 10 distinct foveae as follows: Anterior median fovea elongate, shallow, broadest in posterior 0.5; posterior median fovea shallow, circular. Anterior admedian fovea shallow, circular, open laterally; posterior admedian fovea shallow, oval, orientated anterolaterally. Anterior and posterior adlateral foveae shallow, circular, open laterally. Fields of coarse, deep, setose punctures present close to anterior and posterior margins.

Elytra: Elongate oval, broadest at middle. Subparallel over anterior 0.5, then weakly attenuated to conjointly rounded, narrowly truncate apices. Dorsally flattened, with shallow posterior declivity. Lateral margins explanate and weakly serrate. Elytral series of coarse, shallow punctures, not striate impressed. Serial punctures granulate, with fine, clear setae, reaching next puncture in row; punctures finer posteriorly. Elytral intervals with small, flat, widely-spaced granules, with fine decumbent setae. Granules spaced approx. 1– 2 x spacing of serial punctures. Series 5 and 6 separated by narrow interval. Interval 8 flat, without carina.

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

Venter: Mentum shining, microreticulate, meshes isodiametric in centre and elongate at sides. Surface with scattered, short, erect setae. Anterior margin of mentum, and palpifer with long, erect setae. Submentum shining, with traces of transverse microreticulation. Genae shining, with transverse microreticulation anteriorly; wrinkled behind. Gula shining with transverse microreticulation posteriorly. Prosternum with weak, glabrous central ridge. Remainder rugulose, covered in dense hydrofuge vestiture. pronotal hypomeron broad, weakly shining, with fine isodiametric microreticulation. Mesoventrite and metaventrite with dense hydrofuge vestiture. Mesoventral plaques glabrous, forming inverted Y; stem 0.2 length of arms, latter forming flat, glabrous patches. Metaventrite with shallow elongate median fovea over posterior 0.5; fovea flanked by broad, glabrous patches which extend to posterior margin and connect in a narrow glabrous band apicomedially, anterior to metacoxae. Elytral pseudepipleurs shining, traces of microreticulation; epipleurs shining, ridge-like. Abdominal ventrites 1–4 with dense hydrofuge vestiture. Abdominal ventrite 5 entirely glabrous over central 0.3; hydrofuge vestiture in anterior 0.5 laterally; glabrous part shining, with shallow transverse microreticulation. Junction between pilose and glabrous portions with irregular row of long, golden, decumbent setae. Abdominal ventrite 6 glabrous, with shallow, transverse microreticulation; double, irregular row of golden, decumbent setae approx. 0.4 from apex.

Aedeagus: Elongate, slightly arcuate in ventral view, with parameres attaching close to base and extending almost to the apex of the main piece. Main piece produced on left side in ventral view, thus appearing notched due to gap between this projection and the distal lobe. Distal lobe short, curved to the left in ventral view ( Fig. 2 A).

Female: Somewhat broader than makes, with broader, more strongly explanate elytral margins. Elytral apices with rounded posterolateral angles, and more broadly truncate; sutural angle more strongly emarginated. Glabrous area on metaventrite smaller, restricted to posterior margin. Abdominal ventrite 5 with glabrous area restricted to semicircular patch over posterior 0.4. Glabrous area with irregular row of golden, decumbent setae 0.5 from apex.

Variation: Paratypes vary somewhat in colouration, some being slightly darker, others slightly paler than the holotype.

Differential diagnosis. A member of the barriotum group sensu Perkins & Balfour-Browne (1994) and Perkins (2008), lacking a carina on the 8th elytral interval, and with elytral series 5 and 6 separate throughout. M. caniplenum sp. nov. is morphologically closest to M. drakensbergense Perkins, 2008 [note—automatic emendation of Mesoceration drakensbergensis Perkins ] and M. integrum Perkins, 2008 [note—automatic emendation of Mesoceration integer Perkins ], but differs from M. drakensbergense in its smaller size (BL 1.6–1.75 mm vs. ca. 1.89 mm), distinct colour pattern and aedeagus, which has a more pronouncedly toothed apicolateral projection on the main piece in the new species. M. integrum is approx. the same size as M. caniplenum sp. nov., and also has an aedeagus with a left-sided apicolateral projection on the main piece in ventral view, but like that of M. drakensbergense this is more rounded than that of the new species, as well as being shorter than in either. Externally, M. integrum is distinguished from the new species by its more rounded elytra, which are more highly arched dorsally, with a stronger posterior declivity. In addition, M. caniplenum sp. nov. has smoother elytral intervals, with finer granules, and finer, shallower punctures on the pronotal reliefs.

Distribution. Known to date only from two small streams at Injisuthi, in the uKhahlamba Drakensberg National Park. In the type locality ( Fig. 5 A) the species was found in water trickling over a vertical rock face at the opening of a small gorge formed in a rock outcrop in Afromontane forest. The second locality is at slightly lower altitude than the type locality, where the species was taken below stones in a small stream flowing through montane grassland.

Etymology. From the latin canis (= dog) and plenum (= satisfied; satiated). Injisuthi is an isiZulu name which can translate in English as “place of the well-fed dog”, referring to the formerly abundant game of this area.

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.