Mesoceration foggoi, 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 : 500-501

Mesoceration foggoi sp. nov.

( Figs 1 , 2 , 5 & 6 )

Type locality. South Africa, Western Cape, Matsikammaberg, permanent stream 1 km SE of Sewefontein farm ( Fig. 6 A).

Type material. Holotype (male): “ 21/ix/2014 South Africa WC// Matsikammaberg stream// 1 km SE of Sewefontein farm// permanent D T Bilton leg.” (genitalia extracted and mounted on same card) and red holotype label ( SAM).

Paratypes (36): 13 ♂, 13 ♀ same data as holotype; 6 ♂ “ 21/ix/2014 South Africa WC// Matsikammaberg stream// 1 km NW of Sewefontein farm// D T Bilton leg.”; 1 ♂, 1 ♀ “ 21/ix/2014 South Africa WC// Matsikammaberg seepage stream// over rock at head of Elandskloof// D T Bilton leg.”; 1 ♂ “ 20/ix/2014 South Africa WC// Gifberg—stream in Gifberg Pass// above Vanrhynsdorp// rocky stream D T Bilton leg.”; 1 ♂ “ 20/ix/ 2014 South Africa WC// Gifberg-vertical wet rock face// in Gifberg Pass nr. Vanrhynsdorp// A Foggo leg.” ( CDTB, MCZ, NMW, OUMNH, SAM, SANC, TMSA). All with red paratype labels.

Description. Size: Holotype: BL 1.7 mm; EL 1.05 mm; EW 0.6 mm. Paratypes: ♂s BL 1.65–1.75 mm; EL 1.0– 1.05 mm; EW 0.6–0.65 mm. ♀s BL 1.65–1.85 mm; EL 1.05–1.1 mm; EW 0.6–0.65 mm.

Colour: Dorsum ( Fig. 1 B) with head and pronotum dark piceous brown to black; ocelli slightly paler than rest of head. Elytra paler; orange-brown, suture pitchy, and explanate margins paler. Legs orange-brown, tarsi and femoro-tibial junctions infuscated; tarsal claws pale yellow. Maxillary palpi pitchy brown to black. Venter dark brown to black, with silvery hydrofuge vestiture; pronotal hypomeron and elytral pseudepipleurs paler.

Head: Labrum slightly transverse, rounded apicolaterally with broad apicomedian emargination running approx. 0.4 of length. Sides of apicomedian emargination and anterior angles weakly raised. Surface shining, lacking microreticulation and with scattered fine punctures bearing long white decumbent setae. Frontoclypeal suture strong, arcuate. Clypeus, frons and vertex strongly shining. Clypeus with medium scattered punctures bearing decumbent setae; devoid of microreticulation over central 0.8, with weak longitudinal meshes at lateral margins. Central portion of frons sculptured as central clypeus; punctures slightly larger and sparser. Anteocellar sulci well-marked, broad, open laterally. Sulci and area inside compound eyes rugulosely microreticulated. Ocelli small, shining. Head behind ocelli with sharp declivity. Vertex and occiput rugulose, with transverse microreticulation. Compound eyes large, occupying approx. 0.5 lateral margin of head, 14 ommatidia in longest series.

Pronotum: Cordate, slightly transverse, broadest just before middle. Anterior margin arcuate over median 0.5, without hyaline border; posterior margin straight. Anterior angles obtusely rounded, posterior angles rectangular. Lateral margins sinuated from widest point to base; broadly marginated and crenulate. Surface shining, lacking microreticulation except for areas of transverse meshes in narrow strips in central 0.5 close to anterior and posterior margins. With 10 distinct foveae as follows: Anterior median fovea elongate; posterior median fovea transverse oval. Anterior admedian fovea circular; posterior admedian fovea oval, orientated anterolaterally. Anterior adlateral fovea circular, open laterally; posterior adlateral fovea oval, open laterally. Field of coarse punctures just behind anterior margin in central 0.5, punctures extending into anterior 0.5 of anterior median and anterior admedian foveae. Double row of coarse punctures along posterior margin in central 0.6; remainder of disc with scattered fine—medium punctures bearing long white decumbent setae.

Elytra: Elongate oval, broadest at middle. Subparallel over middle 0.3, then attenuated to truncately rounded apex. Apical angles rounded, slightly emarginated around suture. Sides explanate; minutely serrate. Punctures of elytral series evident to apices; punctures relatively coarse; larger in anterior 0.5. Discal series striate impressed, especially in anterior 0.3. Series 1 and 2 confluent just behind middle, in front of posterior declivity. Series 5 and 6 confluent over anterior 0.3. Serial punctures bearing fine, white, decumbent setae, which reach anterior margin of next puncture in row. Elytral intervals minutely granulate; granules each with fine puncture posteriorly, which bears long, white, decumbent seta which overlaps next seta in row by approx. 0.5 of length. Interval 8 carinate almost to apex.

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

Venter: Mentum weakly shining, rugulosely microreticulate; meshes elongate along lateral margins and isodiametric in centre. Submentum shining, lacking microreticulation. Genae with transverse microreticulation anteriorly; hydrofuge vestiture posteriorly. Gula with transverse, open microreticulation. Prosternum with narrow, distinct, shining and glabrous central ridge. Rest of surface rugulose, with dense hydrofuge vestiture. Pronotal hypomeron broad, shining, lacking microreticulation. Mesoventrite and metaventrite with dense hydrofuge vestiture. Mesoventral plaques glabrous, forming inverted Y. Adlateral and admedian ridges also visible on mesoventrite. Metaventrite with broad, elongate median fovea over posterior 0.5. Metaventrite with small, shining glabrous patch apicomedially, close to metacoxae. Elytral pseudoepipleurs broad, shining, lacking microreticulation; epipleurs shining, ridge-like, with hydrofuge vestiture over anterior 0.2. Abdominal ventrites 1– 4 with dense hydrofuge vestiture. Abdominal ventrite 5 glabrous over posterior 0.8 in central 0.3, with scattered hydrofuge setae and dense, medium punctures bearing long, white, decumbent setae in posterior 0.5 of glabrous patch. Abdominal ventrite 6 shining, traces of transverse microreticulation and double row of irregular punctures along posterior margin, with long, decumbent setae in centre of row, and shorter, stouter, peg-like setae laterally.

Aedeagus: Elongate, with parameres attaching close to base and extending well beyond the apex of the main piece. Main piece relatively broad in ventral view, with strong, stout, curved apical tooth, and long, tube-like distal lobe, extending just beyond the paramere apices. Distal lobe bifurcated approx. 0.25 from apex—this structure being unique so far within the genus ( Fig. 2 B).

Female: Elytra broader and flatter than in males, more strongly explanate along lateral margins. Apex more strongly truncated and emarginated around suture. Abdominal ventrite 5 with glabrous area occupying central 0.3, with weak transverse microreticulation and moderate, medium punctures over apical 0.2, each bearing a yellow decumbent seta. Setae longer centrally; shorter, stouter and peg-like laterally. Anterior tarsi simple.

Variation: Paratypes vary somewhat in colouration, some specimens being paler than the holotype, with yellowish brown elytra and brownish pronotum. This is not, apparently, due to tenerality.

Differential diagnosis. A member of the rivulare group, which would key to M. splendorum Perkins & Balfour-Browne, 1994. Compared to M. splendorum , M. foggoi sp. nov. is larger (BL 1.65–1.85 mm vs. ca. 1.6 mm). Within the rivulare group, the new species can be further distinguished by the elytral series, which are wellmarked throughout, with the discal series striate impressed. The most similar species in size and colouration is M. hantam Bilton, 2014, which has less impressed elytral series, composed of smaller punctures. The aedeagus of M. foggoi sp. nov. is closest to M. rapidense Perkins, 2008 [note—automatic emendation of Mesoceration rapidensis Perkins ] in overall structure, although these species differ in the detail of the apical tooth, and the bifurcated distal lobe of M. foggoi sp. nov. is so far unique within the genus. M. rapidense is also very different externally, with a much narrower forebody than M. foggoi sp. nov., with weak elytral series, which are not striate impressed.

Distribution. Known to date only from a number of localities on the Gifberg-Matsikammaberg massif in the northern part of the fynbos biome of the Core Cape Floristic region ( Manning & Goldblatt 2012). Apparently a relatively common and widespread species in these mountains, found abundantly in all running-water sites investigated in 2014. Taken together with two other apparent regional Gifberg-Matsikammaberg endemics, Mesoceration umbrosum Perkins, 2008 and Mesoceration sewefonteinense sp. nov. Particularly abundant where thin trickles of water flowed over algae-encrusted sheets of sandstone bedrock in stream margins (e.g. Fig. 5 B). Some of the specimens collected were tenerals.

Etymology. Named after my friend and colleague Dr Andy Foggo, who enthusiastically assisted with water beetle sampling on the Gifberg-Matsikammaberg, including the collection of the type series.

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.

FIGURE 6. Habitats of Mesoceration species in South Africa. A) Western Cape, Matsikammaberg, permanent stream 1 km SE of Sewefontein farm— M. foggoi sp. nov., M. sewefonteinense sp. nov., M. umbrosum; B) Western Cape, False Bay, small stream on R 44 road below Boskloof Peak— M. sinclairi sp. nov., M. brevigranum; C) Western Cape, Groote Swartberg, permanent stream below Kangoberg on Gamkaskloof road— M. barriotum, M. littlekarroo, M. reticulatum, M. splendorum; D) Western Cape, Table Mountain National Park, Table Mountain, stream in Echo Valley— M. abstrictum, M. tabulare. Photos D. T. Bilton.