Ranatra heoki, Tran & Poggi, 2019

Tran, A. D. & Poggi, R., 2019, The genus Ranatra Fabricius (Heteroptera: Nepidae) in Borneo, with a redescription of Ranatra spinifrons Montandon and the description of a new species, Zootaxa 4555 (2), pp. 236-246 : 241-244

Ranatra heoki sp.n.

( Figs. 17–27 )

Material examined. HOLOTYPE: male, Malaysia, Sarawak, 38 km towards Simunjan fr. Kuching – Sri Anam Rd, coll. HH Tan, 4 Sep. 1996, THH96100 ( ZRC) . Paratype: 1 male, same locality data as holotype ( ZRC) .

Description. General colouration: mostly brown; eyes dark brown; vertex yellowish brown; all coxae brown and mottled with yellowish brown; fore femur, fore tibia, fore tarsus, middle and hind femora yellowish brown and mottled with brown; middle and hind tibiae and tarsi annulated brown and yellow; ventral surface brown with sparse small whitish mottles.

Measurements: Males: body length 25.5–26.0 (holotype: 25.5); length of siphon 14.0–14.5 (holotype: 14.0); width of head 2.50–2.53 (holotype: 2.53); width of eye 0.84–0.86 (holotype: 0.84); interocular width 0.78–0.84 (holotype: 0.84); anterior width of pronotum 1.94; humeral width of pronotum 2.27; length of anterior lobe of pronotum along midline 5.00; length of posterior lobe along midline 2.00; fore leg: lengths of coxa 4.50, femur 7.45, tibia 3.00, tarsi 0.72; middle leg: lengths of femur 10.50, tibia 9.40, tarsi 1.75; hind leg: lengths of femur 10.80, tibia 13.25, tarsi 1.90.

Head ( Figs. 17, 18 ): Vertex raised above eyes into conical tubercle, the height of the tubercle about a half the height of eye on lateral view; width of eyes about same as interocular width; clypeus, higher than and surpassing lora, anteriorly with a low, conical tubercle; lora bearing long, pale setae along dorsal side, similar setae sparsely on vertex. Antenna: second segment with long, finger-like projection; finger-like projection about three quarters length of third segment.

Thorax: Prothorax in lateral view distinctly longer than fore coxa (about 1.8× the length of fore coxa) and slightly longer than fore femur; anterior lobe 2.2–2.3× as long as posterior lobe when measured along midline; anterior margin of pronotum with a tubercle on each side of midline, distinctly raised when viewed laterally; ratio of humeral width / anterior width about 1.17; posterior lobe with humeri broadly rounded ( Fig. 18 ). Scutellum with length 1.59–1.68× width, posterior section with narrowly rounded apex. Prosternum with low median carina on anterior part, anterior margin straight. Mesosternum with a pair of low tubercles on anterolateral margin, posterior projection between middle coxae truncate, weakly grooved along midline. Metasternum with anterior part weakly grooved along midline, posterior part slightly raised medially and grooved laterally, posterior margin deeply emarginated ( Fig. 19 ). Space between middle coxae narrower than that between hind coxae. Hemelytra uniformly textured, mostly brown, with membrane only reaching mid-length of abdominal tergum VI.

Legs: Fore femur ( Figs. 20–23 ): slender, widest at basal part, ratio of maximum width at basal part / maximum width at distal part: 1.15–1.17 (holotype: 1.17); ventral margin with a long median carina bearing dense short setae and a tooth on mesal surface situated distally to median carina; distal part with a very small black tooth on lateral surface of ventral margin, before pre-apical constriction on ventral margin, distal tooth shorter than setae on ventral side of femur; ratio of width of femur across median tooth (excluding tuft of setae) / width of femur at basal half: 1.00–1.06 (holotype: 1.06); ratio of width of femur across median tooth / width at base of tooth at distal side: 1.43– 1.55 (holotype: 1.43); ratio of width of femur across median tooth / width of femur across median carina (excluding setae, on proximal side of median tooth): 1.15–1.25 (holotype: 1.25). Middle femur subequal in length to hind femur; hind femur not reaching posterior margin of abdominal sternum VI when folded back parallel to body. Middle tibia shorter than middle femur; hind tibia longer than hind femur; middle and hind femora both bearing sparsely distributed long, thin, pale hairs along their lengths; middle and hind tibiae both bearing dense fringe of long hairs on posterior margins along their entire lengths.

Abdomen: Operculum of male ( Fig. 24 ) about as long as connexivum, medially keeled, apex pointed. Respiratory siphon with only sparse long, thin hairs along its length, not formed into a fringe.

Male genitalia: Paramere ( Figs. 26, 27 ): dorsoventrally thick, dorsal surface almost straight; strongly constricted at distal quarter before a broadly curved apical hook, inner side of the curve with short setae; apex of hook rounded; ventral side of paramere before apical hook bearing a sub-triangular elevation, with long setae. Phallotheca moderately sclerotised, as in Fig. 25 .

Female: Unknown.

Etymology. The new species is dedicated to Dr. Tan Heok Hui (Lee Kong Chian Natural History Museum), for his significant contribution to the water bug collection in the LKCNHM, including numerous samples of Ranatra .

Discussion. Ranatra heoki sp.n. also belongs to the R. gracilis species group (sensu Lansbury, 1972). It can be easily distinguished from other taxa of this species group by the following characteristics: (a) the height of the tubercle on the vertex is about a half the height of an eye in lateral view; (b) the clypeus has a small, but distinct tubercle above the lora ( Fig. 17 ); and (c) the paramere is dorsoventrally thick, with the dorsal surface almost straight, and strongly constricted at the distal quarter before a broadly curved apical hook, and its subapical process is sub-triangular, bearing long setae ( Figs. 26, 27 ).

Among taxa of the R. gracilis group, the general appearance of the paramere of this new species is most similar to that of R. schuhi from Myanmar. However, it can be easily distinguished from R. schuhi by the following characteristics: Ranatra heoki sp.n. has a shorter body, with length excluding siphon ca. 25 mm (in R. schuhi , body length is ca. 32 mm). The clypeus of the new species has a small tubercle above the lora (in R. schuhi , the clypeus above the lora is flat and without a tubercle). The ratio of length of the anterior pronotal lobe to length of the posterior protonal lobe is greater in R. heoki sp.n. (2.2–2.3: 1.0) than in R. schuhi (ca. 1.9: 1.0). In the new species, the pair of tubercles at the anterior margin of the mesosternum is less prominent than that in R. schuhi . The hemelytra of R. heoki sp.n. is uniformly textured, mostly brown and shorter, and the membrane reaches only midlength of abdominal tergum VI (hemelytra of R. schuhi is reddish brown with yellow maculated marks and longer, and the membrane reaches to the posterior margin of abdominal tergum VI). The fore femur of R. heoki sp.n. does not widen distally, the maximum width anterior to the median tooth is less than the maximum width posterior to the median tooth (in R. schuhi , the fore femur widens distally, with the maximum width anterior to the median tooth greater than the maximum width posterior to the median tooth). In R. heoki sp.n., the median tooth of fore femur is more prominent, the width of the femur across the median tooth is slightly greater than the maximum width of the basal part of the femur (in R. schuhi , the width of the femur across the median tooth is subequal to the maximum width of the basal part of the femur). The hind femur of R. heoki sp.n. is shorter and does not reach the posterior margin of abdominal sternum VI when folded back parallel to abdomen (the hind femur of R. schuhi is longer, reaching the anterior half of the operculum). In R. heoki sp.n., the respiratory siphon has only sparse setae along its ventral margin, without a fringe of dense erect setae (in R. schuhi , the respiratory siphon has a fringe of erect setae along the ventral margin in the basal half).

The parameres of these two species have a similar general appearance, but they differ in the following details. The paramere of R. heoki sp.n. is dorsoventrally thicker; its dorsal surface is almost straight, not sinuate, and is constricted in the distal quarter; its distal hook is shorter, with a more open curve, directing its apex ventrad; and the subapical process is more acute, and sub-triangular. In contrast, the paramere of R. schuhi is sinuate in the basal part and is constricted in the distal third; its distal hook is longer and recurved, directing its apex anteroventrad; and the subapical process is round.

Female specimen is not available for comparison.

Distribution. Borneo: Sarawak.

Figures

FIGURES 17–27. Ranatra heoki sp.n. (17) head and prothorax, lateral view. (18) head and prothorax, dorsal view. (19) metasternum. (20, 21) left fore leg and femoral teeth, lateral view. (22, 23) left fore leg and femoral teeth, mesal view. (24) operculum. (25) phallotheca. (26) paramere. (27) apical part of paramere. (scale bars: 17, 18, 20, 22 same scale; 21, 23 same scale; 19, 24 same scale).