Rhithrops capensis, Bilton & Shepard, 2022

Bilton, David T. & Shepard, William D., 2022, Rhithrops capensis gen. et sp. nov., a new aquatic dryopid beetle from the Western Cape of South Africa (Coleoptera: Dryopoidea: Dryopidae), Zootaxa 5195 (6), pp. 539-553 : 541-546

Rhithrops capensis sp. nov.

( Figs 1–9 )

Type locality. South Africa, Western Cape, Cederberg, Matjies Rivier, Matjiesrivier , 32°31’07.42”S 19°21’00.4”E, 725 m. ( Fig. 9 ) .

Type material. Holotype (male): “ 22/ix/2011 South Africa WC// Cederberg , Matjies Rivier // Matjiesrivier 32°31’07.42”S // 19°21’00.4”E, 725 m. D T Bilton leg.” ( AMG).

Paratypes (23): 5♂, 10♀ same data as holotype ; 1♀ “ 21/ix/2010 South Africa WC// Cederberg, Matjies Rivier // Matjiesrivier 32°31’07.42”S // 19°21’00.4”E, 725 m. D T Bilton leg.” ; 2♂, 3♀ “ 22/ix/2011 South Africa WC// Cederberg, Matjies Rivier // Matjiesrivier 32°31’07.42”S // 19°21’00.4”E, 725 m. D T Bilton leg.” ; 1♂, 1♀ “ South Africa: W. Cape // Cederberg, Maalgat // Matjiesrivier // 28-29 XII 2004 820 m asl // 32°29’40”S 19°16’49”E // P. S. Cranston, leg.” ( AMG, CBP, DMSA, EMEC, NMW) .

Description: With all the above characters of the genus.

Size: Holotype: BL 4.10 mm; EL 2.65 mm; EW 1.35 mm; PL 0.85 mm; PW 1.20 mm. Paratypes: Males BL 4.40–4.75 mm; EL 2.60–3.00 mm; EW 1.45–1.60 mm; PL 0.85–1.05 mm; PW 1.20–1.35 mm. Females BL 4.65– 4.80 mm; EL 2.75–2.90 mm; EW 1.40–1.60 mm; PL 0.90–1.05 mm; PW 1.25–1.35 mm.

Head: Epicranium densely and shallowly punctate, with short decumbent setae, epicranial suture absent; frontal area twice as wide as one compound eye, antennal ridges absent, frontoclypeal suture straight between antennal bases.

Elytra: Conjointly twice as long as wide, parallel-sided, apices moderately protruding ( Figs 1 & 6D–E ).

Legs: Relatively long, elongate, with large, strongly-developed tarsi and claws ( Fig. 8A–C ).

Male: Last abdominal ventrite with broad, shallow apicomedial emargination ( Fig. 7E ). Labium with modified, spathulate setae on anteroventral margin ( Fig. 4F ). Anterior edge of sternite 8 with short median strut ( Fig. 9F ); sternite 9 as in Fig. 9C . Tergite 8 with numerous long setae close to posterior margin ( Fig. 9E ).

Aedeagus: Long and tubular ( Figs 8D–F & 9A, B & D ); basal piece:paramere ratio 0.6:0.4. Basal piece hookshaped basally, open on left side. Median lobe long, narrow, acute apically. Parameres parallel-sided, apically a little longer than median lobe, apices rounded on outer side, clasping apex of median lobe ( Fig. 8F ).

Female: Few external differences to males. The sublateral furrows of the pronotum are deeper and more evident ( Fig. 2B ). The last abdominal ventrite has a conical apex, somewhat raised centrally and lacks an apicomedian emargination ( Fig. 7F ). The labium has fewer, shorter modified setae on the anteroventral margin ( Fig. 4E ). Sternite 8 as in Fig. 10C .

Ovipositor: Elongate ( Fig. 10A–B ) and strongly sclerotized; type 1 (sensu Kodada et al. 2016); apically sharp-tipped. Valvifers ventral, asymmetrical, long, thin, forming a V-shaped sclerite. Coxites asymmetrical, laterally compressed, blade-shaped, apex very acute, dorsal side serrate, with basally directed long narrow dorsal extension.

Distribution and habitat. Known only from type locality, the Matjies River ( Fig. 11 ), a tributary of the Olifants River in the Cederberg, Western Cape Province, South Africa.

Etymology. The trivial name, capensis , refers to location of this species in the Western Cape Province of South Africa.

Figures

FIG. 1. Rhithrops capensis gen. et sp. nov., Holotype habitus. Scale bar = 1 mm.

FIG. 2. South African endemic dryopid genera, dorsolateral view of pronotal margins. A) Rhithrops capensis gen. et sp. nov., holotype male; B) Rhithrops capensis gen. et sp. nov., paratype female; C) Rapnus sp., female; D) Strina sp., female. C) & D) South Africa, Western Cape, Franschoek, Mont Rochelle. Scale bar = 0.5 mm.

FIG. 3. Rhithrops capensis gen. et sp. nov. A) head, posterolateral view; B) compound eye – arrow indicates inter-ommatidial seta; C) detail of dorsolateral sculpture of head, inside compound eye; D) antennae; E) antennomeres 1–2; F) antennomeres 3–10.

FIG. 4. Rhithrops capensis gen. et sp. nov. A) labrum, dorsal view; B) right mandible, ventral view; C) right maxilla, dorsal view; D) close-up of maxillary palp apex; E) female labrum and mentum, ventral view; F) male labrum and mentum, anteroventral view.

FIG. 5. Rhithrops capensis gen. et sp. nov. A) right mandible, ventrolateral view – teeth numbered as in text; B) left mandible, ventral view – pt = prostheca, Lf = lateral flange. Scale bar = 100 μm.

FIG. 6. Rhithrops capensis gen. et sp. nov. A) prothorax, dorsal view; B) close-up of sculpture of pronotal disc; C) Meso and metanotum, with scutellum; D) right elytron, dorsolateral view; E) detail of right elytral apex; F) prothorax, ventral view.

FIG. 7. Rhithrops capensis gen. et sp. nov. A) meso and metaventrites, ventral view; B) male abdomen, ventral view; C) female abdomen, ventral view; D) close-up of plastron vestiture at junction of abdominal ventrites 2–3; E) male abdominal apex; F) female abdominal apex.

FIG. 8. Rhithrops capensis gen. et sp. nov. A) male foreleg, ventral view; B) male foretarsus and tibial apex, ventral view; C) male hind tibia and tarsus, ventral view; D) aedeagus, ventral view; E) aedeagus, lateral view; F) aedeagal apex, ventral view.

FIG. 9. Rhithrops capensis gen. et sp. nov. A) aedeagus, ventrolateral view; B) aedeagus, lateral view; C) male sternite 9; D) aedeagal apex, ventral view (not to scale); E) male tergite 8; F) male sternite 8. Scale bars = 0.5 mm.

FIG. 10. Rhithrops capensis gen. et sp. nov. A) ovipositor, lateral view; B) ovipositor apex, lateral view (not to scale); C) female sternite 8. Scale bar (A & C) = 0.5 mm.

FIG. 11. Rhithrops capensis gen. et sp. nov. Type locality, South Africa, Western Cape, Cederberg, Matjies Rivier, Matjiesrivier, 32°31’07.42”S 19°21’00.4”E, 725 m. Photo D T Bilton.