Rhithrops capensis gen. et sp. nov., a new aquatic dryopid beetle from the Western Cape of South Africa (Coleoptera: Dryopoidea: Dryopidae) Author Bilton, David T. 0000-0003-1136-0848 School of Biological and Marine Sciences, University of Plymouth, Drake Circus, Plymouth PL 4 8 AA, UK. d. bilton @ plymouth. ac. uk; https: // orcid. org / 0000 - 0003 - 1136 - 0848 & Department of Zoology, University of Johannesburg, PO Box 524, Auckland Park, Johannesburg 2006, South Africa. d.bilton@plymouth.ac.uk Author Shepard, William D. 0000-0003-4664-2597 Essig Museum of Entomology, 1101 Life Sciences Bldg. # 4780, University of California Berkeley, CA 94720 USA. William. Shepard @ csus. edu; http: // orcid. org / 0000 - 0003 - 4664 - 2597 hepard@csus.edu text Zootaxa 2022 2022-10-17 5195 6 539 553 journal article 168727 10.11646/zootaxa.5195.6.3 893c13e2-2785-463d-b114-a499cbe8a7c8 1175-5326 7223884 EB51F148-8EFC-4B22-9B74-1DBE4EB3A544 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 ) . 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. 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. 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. 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 ). 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. 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 .