Ranatra brevicauda, Tran & Zettel, 2021

Tran, A. D. & Zettel, H., 2021, Taxonomic review of the Ranatra gracilis group sensu Lansbury, 1972 (Nepomorpha: Nepidae), with descriptions of four new species, Raffles Bulletin of Zoology 69, pp. 45-70 : 57-61

Ranatra brevicauda , new species

( Figs. 1D , 5 , 6 )

Material examined. Holotype (male): “ Philippines: Leyte \ Hilusig, rivers\ leg. H. Zettel ” ( PNM).

Paratypes ( NHMW, UPLB, ViSCA, ZCW, ZRC): PHILIPPINES: Leyte : 10 males, 9 females, Leyte Province, same collecting data as holotype ; 1 male, Leyte Province, east of Ormoc, Lake Danao ; 1 male, 1 female, Leyte Province, Makinhas, river ; 2 males, 3 females, Leyte Province, Makinhas, Pacdanganan River ; 1 female, Leyte Province, rivers at Hilusig ; 3 males, 2 females, Leyte Province, Hilusig, Mahaplag ; 1 male, Leyte Province, Baybay, ViSCA, 50 m a.s.l., stream near Forestry ; 1 male, Southern Leyte Province, east of Sogod , large stream ; 1 male, 2 females, Southern Leyte Province, north of Maasin, small stream east of Lonoy ; 1 male, Southern Leyte Province, Amparo, Amparo River near bridge . Biliran: 1 female, Biliran Province, Caibiran, road to Naval, Mainit, stream . Samar: 2 males, Northern Samar Province, Veriato, El Amigo, Veriato Falls . Luzon : 1 male, Sorsogon Province, Ticol, west of Sorsogon City ; 10 males, 6 females, Albay Province, 40 km N Legaspi, 1 km W Malilipot, Busai Falls ; 1 male, Camarines Sur Province, 20 km east of Naga, 3 km east of Carolina, Mainit Spring (at “Hydro”) ; 1 male, 1 female, Camarines Sur Province, Lagonoy, 1 km west of San Sebastian, Kinayangan River ; 1 female, Camarines Sur Province, Lupi, Sooc, near Bicol NP ; 1 male, 1 female, Camarines Sur Province, Lupi, Sooc, creek near dam ; 1 female, Camarines Sur Province, Lupi, Sooc. Description. General colouration: mostly light brown to brown; eyes dark brown; all coxae brown; all femora and tibiae usually distinctly annulated brown and yellow; fore tarsus yellowish brown, darker at apex; apices of middle and hind tibiae, middle and hind tarsi dark brown. Hemelytra uniformly textured, light coloured or brown .

Measurements. Males: body length 29–33 (holotype: 32); length of siphon 7.1–9.7 (holotype: 8.9); width of head 2.53–2.77 (holotype: 2.72); interocular width 0.95–1.07 (holotype: 1.04); width of eye 0.78–0.89 (holotype: 0.84); pronotal length 8.08, anterior pronotal length 6.67; posterior pronotal length 2.92; anterior width of pronotum 2.41; posterior width of pronotum 2.95; lengths of leg segments: fore leg: coxa 5.17, femur 8.33, tibia 3.67, tarsus 0.74; middle leg: femur 11.7, tibia 10.7, tarsus 1.92; hind leg: femur 12.1, tibia 13.4, tarsus 1.87.

Females: body length 35–40; length of siphon 8.3–11.3; width of head 2.64–3.02; interocular width 1.04–1.20; width of eye 0.80–0.97; pronotal length 8.42, anterior pronotal length 6.75; posterior pronotal length 3.33; anterior width of pronotum 2.51; posterior width of pronotum 3.16; lengths of leg segments: fore leg: coxa 5.33, femur 8.83, tibia 3.92, tarsus 0.98; middle leg: femur 12.3, tibia 11.4, tarsus 1.92; hind leg: femur 12.7, tibia 14.25, tarsus 2.12.

Head ( Fig. 5B, C ): Vertex above eyes with an obtuse tubercle, narrow in dorsal view; width of eye clearly less than interocular width; clypeus smooth and convex, in lateral view slightly lower than lora and slightly surpassing lora anteriorly; lora swollen, with a small, but distinct dorsal nodule, bearing very few sparse, long, pale setae along dorsal side (nodule less distinct in some samples). Antenna ( Fig. 5A ): finger-like projection of second antennal segment about one third the length of third segment.

Thorax: Prothorax in lateral view distinctly longer than fore coxa (about 1.5–1.7× the length of fore coxa) and about 0.9–1.1× the length of fore femur; anterior lobe about 1.86–2.28× as long as posterior lobe; anterior collar of pronotum distinctly raised and bituberculate; ratio of posterior width / anterior width 1.17–1.29; posterior lobe with humeri broadly rounded, on each sublateral side with two swellings separated by a longitudinal groove ( Fig. 5B, C ). Scutellum with length ca. 1.83–2.14× width, usually swollen at midpoint followed by a transverse depression before posterior third, apex pointed. Prosternum with paired broad, shallow longitudinal depressions separated by low and blunt median carina; median carina rather indistinct in posterior half. Mesosternum slightly raised on anterolateral margin, posterior projection between middle coxae truncate, weakly grooved along midline. Metasternum with anterior part grooved along midline, posterior part distinctly raised along midline and grooved sublaterally, posterior margin angularly emarginated ( Fig. 5F ). Space between middle coxae subequal to or slightly greater than that between hind coxae. Hemelytra: membrane only reaching anterior third of abdominal tergum VI.

Legs: Fore femur ( Fig. 5D, E ): in both sexes relatively thick (ratio of length / maximum width of femur: 9.9–11.5, holotype 10.7), widest at basal part, distal part nearly as wide as basal part, ratio of maximum width at basal part / maximum width at distal part in males: 1.07–1.17 (holotype 1.11), in females: 1.09–1.42; flexor side with a median carina bearing dense short setae and a tooth on mesal (anterior) surface situated distally to median carina; distal part with a pair of small teeth on lateral (posterior) surface of flexor side, proximal to sinuous pre-apical margin; distal teeth slightly longer than surrounding setae on flexor side of femur (more prominent in female); ratio of width of femur across median tooth (excluding tuft of setae) / width of femur at basal part: 0.97–1.16 (holotype 1.05); ratio of width of femur across median carina (excluding setae) / width of femur at basal part: 0.78–1.00 (holotype 0.95). Middle femur slightly shorter than hind femur; hind femur, when folded back parallel to body at most reaching to anterior third of abdominal sternum VI (in males) or at most slightly surpassing posterior margin of sternum V (in females). Middle tibia shorter than middle femur; hind tibia longer than hind femur; middle and hind tibiae both bearing dense fringes of long hairs on posterior margins along their distal two-thirds.

Abdomen: Operculum of male ( Fig. 5G ) slightly shorter than connexivum, sometimes reaching end of connexivum, medially keeled, apex pointed. Sternum VI of female with median keel distinctly raised at posterior half. Operculum of female clearly longer than connexivum, surpassing the apex of connexivum of about one third the length of operculum. Respiratory siphon clearly shorter (0.65–0.91×) than the length of sterna III–V combined, with sparse long, thin hairs along its length, more on apical part.

Male genitalia: Paramere ( Fig. 6 ): dorso-ventrally strongly thickened at basal third, constricted at distal third; ventral margin gradually tapering from basal third towards the constricted part, then followed by a large, acute trapezoidal process bearing tuft of setae; on inner face, pre-apical process bearing a pointed projection slightly shorter than tuft of setae; apical hook long, slender, broadly curved with narrow, rounded tip; dorsal margin of paramere sinuate, degree of sinuosity varying among populations, from slightly convex to strongly convex at constricted distal section of the paramere ( Fig. 6A, D, G, J ). Phallotheca strongly sclerotised.

Etymology. The species epithet is composed of the Latin adjective brevis (= short) and the Latin noun cauda (= tail) and refers to the short siphon of this species.

Remarks. The paramere is similar to that of R. bendanilloi , new species. See also Remarks under R. pangantihoni , new species.

Distribution. Philippines: Greater Mindanao region: Leyte, Biliran, Samar; extending northwards to Greater Luzon region: Southern Luzon (Camarines Sur, Albay, Sorsogon).

Figures

Fig. 1. Habitus of Ranatra spp., all males. A, R. stali Montandon, 1905; B, R. bisaya, new species; C, R. bendanilloi, new species; D, R. brevicauda, new species; E, R. pangantihoni, new species (all of same scale).

Fig. 5. Ranatra brevicauda, new species, male. A, antenna; B, C, head and prothorax, lateral and dorsal views; D, E, fore femur, lateral and mesal views; F, metasternum; G, operculum. (B, C same scale; D, E same scale; F, G same scale).

Fig. 6. Parameres of Ranatra brevicauda, new species, of specimens from various localities. A–C, from Leyte; D–F, from Samar; G–I, from Sorsogon; J–L, from Albay. A, D, G, J, lateral view; B, E, H, K, apical part, sub-caudal view; C, F, I, L, apical part, inner view (all of same scale).