Elmomorphus sarawakensis Chujo & Sato 1964

Elmomorphus sarawakensis Chûjô & Satô, 1964 Figs 14, 15, 16, 19 F Elmomorphus sarawakensis Chûjô & Satô, 1964: 193. Material examined. Holotype. Malysia – Sarawak • male; “ Kaleti SARAWAK ”; 30 Jan. 1962; G. Imadate leg.; OMNH. Additional material. Malaysia – Sabah • 1 male; R. Karamuak, 7 km SSE Telupid; 1–7 Sep. 1977; M. E. Bacchus leg.; at light; NHMUK – Sarawak • 8 males, 14 females; Mulu NP, stream near Deer Cave [19]; 3 March 1993; M. Jäch leg.; NMW, CKB • 8 males, 10 females; Mulu NP, near base camp; May – Sep. 1978; P. M. Hammond & J. E. Marshal leg.; at light; NHMUK • 1 male; Mulu NP, Long Melinau env. [site 17]; Mar. 1978; J. D. Holloway et al. leg.; low secondary forest on riverbank; NHMUK • 2 females; Mulu NP, Camp 2. [site 13]; Feb. 1978; J. D. Holloway et al. leg.; mixed dipterocarp forest; NHMUK • 10 males, 12 females; Batu Niah; 12 Dec. 1968; M. Satô leg.; CSN • 15 specimens; Mulu NP, Paku River [41]; 04.037183°N, 114.828933°E; alt. 70 m; 12 Oct. 2018; J. Kodada & D. Selnekovič leg.; CKB, JK 55, JK 1852 to JK 1854. Diagnosis. Elmomorphus sarawakensis (Fig. 14) ranks among the largest species of the genus, measuring 3.90–4.46 mm in total length. The dorsal plastron scales (PS, Fig. 15 B) are interspersed with flat, lustrous tubercles (T, Fig. 15 B), together covering the entire cranial surface, the lateral margins of the pronotum, and most of the elytral surface, except for a narrow, subtriangular area along the suture in the anterior half. Males are distinguished by a transverse row of prominent long setae on the labrum (Fig. 15 A), a cluster of moderately elongate setae at the base of the protrochanter (Fig. 15 C), and a distinctly concave metaventral disc (Fig. 15 D). Females lack long setae on the labrum and protrochanter, the metaventral disc is flat to moderately convex (Fig. 15 E), and the elytral apices are produced and bent ventrad to fit into the apical emargination of ventrite 5. The aedeagus is characterised by a markedly enlarged, bulbous proximal portion of the phallobase with complex sclerotisation and a comparatively small, laterally positioned basal orifice (Fig. 16). This combination of features is unique among all known species of Elmomorphus. Elmomorphus sarawakensis is readily identifiable by its COI DNA barcode, which shows clear separation from all other examined species. Its nearest neighbour is E. striatellus, from which it is separated by an interspecific p - distance of 12.67–13.41 %; the maximum intraspecific divergence is 0.97 % (Suppl. material 4). The species is further characterised by unique sequences at the 28 S, ITS 2, and CAD loci. Re-description. Measurements (mm): TL: ♂♂ 3.90–4.22 (4.04 ± 0.14, n = 4), ♀♀ 4.13–4.26 (4.18 ± 0.06, n = 5); PL: ♂♂ 0.92–1.03 (0.98 ± 0.05, n = 4), ♀♀ 0.88–1.01 (0.96 ± 0.05, n = 5); PW: ♂♂ 1.52–1.63 (1.60 ± 0.05, n = 4), ♀♀ 1.60–1.65 (1.62 ± 0.02, n = 5); EL: ♂♂ 3.01–3.26 (3.10 ± 0.11, n = 4); ♀♀ 3.12–3.34 (3.25 ± 0.08, n = 5); EW: ♂♂ 1.87–1.94 (1.92 ± 0.04, n = 4), ♀♀ 1.91–1.96 (1.93 ± 0.02, n = 5); PhL: 1.38–1.41 (n = 2); PrL: 0.48–0.50 (n = 2). Habitus (Fig. 14). Body elongate-ovate, widest near the middle of the elytra, dorsally convex. Dorsal integument dark brown to black (in mature specimens collected from water); mouthparts, antennae, and legs reddish-brown; ventral side reddish-brown. Pubescence consisting of short, decumbent, yellowish setae. Dorsal plastron scales (PS, Fig. 15 B) cover the entire cranial surface, the lateral sides of the pronotum, and most of the elytral surface, except for a narrow, subtriangular area along the suture in the anterior half; plastron scales intermixed with flat, lustrous tubercles (T, Fig. 15 B). Ventral plastron setae present on the ventral surface, except for the prosternal process, the median portions of the prosternum and metaventrite, and the median parts of ventrites 1 and 2. Head with small, round setiferous punctures (Fig. 15 A, B) distinctly smaller than the eye facets, associated with flattened, smooth tubercles separated by 1–3 × facet diameter; cranial surface entirely covered with plastron scales. Labrum transverse, setose; in males with a transverse row of conspicuous long setae (Fig. 15 A). Anterior margin of clypeus arcuate. Eyes oval, large, protruding (Fig. 15 A); ocular index: ♂♂ 2.01–2.25 (2.14 ± 0.08, n = 14), ♀♀ 1.90–2.12 (1.99 ± 0.07, n = 16). Antennae 11 - segmented. Pronotum transverse, widest at base, moderately convex; PW / PL: ♂♂ 1.59–1.68 (1.64 ± 0.04, n = 4), ♀♀ 1.62–1.83 (1.69 ± 0.08, n = 5); surface smooth, with round setiferous punctures less coarse than the eye facets, becoming moderately larger and nearly rasp-like posteriorly. Lateral sides covered with plastron; the plastron bands narrowed posteriorly, each covering ~ 1 / 3 of pronotal width near the anterior margin and ~ 1 / 5 near the posterior margin. Anterolateral portions strongly deflexed, anterior angles strongly produced. Lateral margins convergent, nearly straight. Prosternal process smooth, with moderately raised lateral sides; median keel moderately convex; evenly setose in both sexes. Scutellum smooth, with small setiferous punctures. Metaventrite covered with plastron except for the median portion. Metaventral disc concave in males, flat to weakly convex in females, evenly setose in both sexes; metaventral process with weakly raised lateral margins (Fig. 15 D, E). Elytra widest at approx. the middle; EL / EW: ♂♂ 1.57–1.68 (1.62 ± 0.05, n = 4), ♀♀ 1.62–1.73 (1.68 ± 0.04, n = 5); in females, the apices produced and bent ventrad, fitting into the apical emargination of abdominal ventrite 5. Surface covered with plastron except for a narrow, subtriangular area along the suture in the anterior half; at its widest, this area spans ~ 1 / 3 of the elytral width and extends slightly beyond the midpoint towards the apex. Faint traces of longitudinal striae present in some specimens. In males, the protrochanter bears a cluster of dense, moderately elongate setae (Fig. 15 C). Tibiae straight; protibia ~ 1.5 × as long as protarsus; terminal protarsomere as long as all preceding tarsomeres combined; claws ~ 0.4 × as long as the terminal protarsomere. Abdominal ventrites covered with plastron except for the median portions of ventrites 1 and 2 (Fig. 15 D, E); admedian keels on ventrite 1 absent. Ventrite 5 in males subtruncate or very shallowly emarginate at apex; in females deeply emarginate. Aedeagus (Fig. 16) very distinctive. Distal portion of phallobase tubular, markedly long and narrow, with strongly sclerotised dorsal and lateral walls, the median ventral area largely membranous. Proximal portion of phallobase strongly expanded and bulbous, appearing to consist of several parts with complex sclerotisation; basal orifice small and laterally positioned. Parameres slender, strongly bent ventrad in their posterior half, with flat admedian faces and narrow, subacute apices (in lateral aspect); PhL / PrL 2.82–2.85 (n = 2). Penis narrow, reaching to the apical quarter of paramere length, gradually narrowed from base to an acuminate apex (in ventral aspect). Fibula narrow but distinct, present in the membranous median area of the phallobase. Bursa copulatrix with a longitudinal cluster of minute, densely arranged spines on each side (Fig. 19 F). Secondary sexual dimorphism. Males with long setae on the labrum and protrochanter (Fig. 15 A, C); metaventral disc concave; ventrite 5 subtruncate or shallowly emarginate at apex. Females without clusters of long setae; metaventral disc flat to weakly convex; elytral apices produced and bent ventrad; ventrite 5 deeply emarginate at apex (Fig. 15 E). DNA sequences. Three sequences of COI, two of 28 S, and two of CAD have been deposited in GenBank and BOLD; accession numbers are listed in Suppl. material 1. (No ITS 2 sequence was obtained for this species.) Distribution. Malaysia (Sabah, Sarawak). Habitat and syntopic species. In Mulu National Park, Sarawak, specimens were collected from the Paku River, a shallow stream running through primary forest (Fig. 3 E), on submerged dead logs, together with two species of Stenomystax.