Pleciobates bengalensis Jehamalar, Basu & Zettel

Jehamalar, E. Eyarin, Chandra, Kailash, Zettel, Herbert, Basu, Srimoyee, Barman, Bijita, Gupta, Susmita & Subramanian, K. A., 2014, Two new species of Pleciobates (Hemiptera: Gerromorpha: Gerridae) from India, with a key to the species of Pleciobates, Zootaxa 3866 (3), pp. 435-445 : 437-440

Pleciobates bengalensis Jehamalar, Basu & Zettel , NEW SPECIES

( Figs. 1A–M )

Material examined. Holotype (apterous male): INDIA, WEST BENGAL, Jalpaiguri District, Alipurduar Division, Raidak River, 26.488474 N, 89.692725 E, alt. 51 m, 19.iv.2013, coll. Srimoyee Basu. Paratypes 14 apterous male, 1 apterous female, same data as for holotype; 2 apterous females, Buxa Tiger Reserve, Damanpur Forest, Dima River, 26.6353 N, 89.50495 E, alt. 85 m 17.iv.2013, coll. Srimoyee Basu; 4 apterous males, 1 apterous female, Jalpaiguri District, Alipurduar Division, Sikuiajuora stream, 26.586383 N, 89.557166 E, alt. 65 m, 17.iv.2013, coll. Srimoyee Basu.

Repository. The type specimens are deposited in the CEL, ZSI, New Alipore, Kolkata, West Bengal, India. Holotype Reg. No. 3453/H15 and Paratypes Reg. No. 3444/H15 to 3446/H15.

Etymology. Pleciobates bengalensis is named after West Bengal, where the species has been collected.

Diagnosis. The males of Pleciobates bengalensis sp. nov. can easily be distinguished from the most closely related species, P. expositus , by a prominent silvery white fascia on each side of the sublateral region of the mesonotum; the straight posterior margin of abdominal tergite VII; the concave posterior margin of tergite VIII; and the structure of endosomal sclerites. Further, females can be identified by the well developed, erect metanotal tubercle that reaches to the middle of abdominal tergite I and possesses a blunt tip; by the relatively long hairy process of the sixth connexival segment; and by the straight and wide posterior margin of abdominal sternite VII.

Description. Apterous male (holotype measured; range of five specimens given in parentheses for some characters): ( Figs. 1A, D, E, H–L ). Body length 6.21 (6.07–6.90); body width (across mesoacetabula) 1.80 (1.80–1.76).

Colour. Dorsum of body dark brown to black except yellowish brown head (with a crown-shaped black mark in front of eyes), pronotum with yellow median oblong mark; mesonotum sublateral region with posteriorly widened silvery white fascia; posterior region of acetabula and posterior region of abdominal segment VIII to tip of abdomen yellowish brown. Venter pale yellowish brown except anterior three fourths of mesosternum black, mesosternum one fourth from the posterior region with W-shaped angulated yellowish brown mark, prominent in alcohol. Eyes black. Antenna black. Rostrum yellowish brown except apex of third and entire fourth segment black. Legs: coxa and trochanter of all legs yellowish brown; forefemur yellow with two brown to black broad stripes fused apically; foretibia and foretarsus black; mid and hind legs black except yellowish brown base of midfemur. Dorsum of body clothed with minute silvery white hairs, prominent on meso- and metanotal sulcations and on abdominal tergites, more pronounced on median junctions between metanotum and first abdominal tergite and between first and second abdominal tergites.

Structural characters. Head length 0.85, maximum head width across eyes 1.14; minimum interocular width 0.40; eye length 0.54, eye width 0.33. Head apex slightly produced in dorsal aspect; antennal tubercle well developed. Dorsum of head with rows of few setae from base of antennal tubercle along inner eye margins to base of head. Rostrum not surpassing forecoxa. Lengths of antennal segments I–IV, 3.09 (2.69–3.09), 0.81 (0.55–0.81), 0.80 (0.75–0.87), 0.76 (0.64–0.76); base of first antennal segment at lower margin with one long and a few short setae; fourth antennal segment with two to four evenly distributed, short setose spines along outer concavity; antennal segments two and three without setae.

Pronotum with anterior margin almost straight and posterior margin straight to concave; pronotal length 0.59 (0.58–0.61), pronotal width 1.20. Prosternal length 0.38, mesonotal length 1.94 (1.89–2.09); mesosternal length 2.74, metanotal length 0.58 (0.58–0.64); metasternal length 0.24. Meso- and metanota with median longitudinal sulcus, clothed with minute silvery white hairs; combined length of meso- and metanota 2.52 (2.50–2.67).

Lengths of legs segments: foreleg: femur 3.14 (2.92–3.14), tibia 2.42 (2.20–2.42), tarsus I–II 0.84 (0.78–0.84), 0.55 (0.54–0.57); mid leg: femur 9.68 (8.87–9.68), tibia 4.60 (4.27–4.60), tarsus I–II 1.73 (1.53–1.78), 0.41 (0.35–0.41); hind leg: femur 8.77 (8.10–8.77), tibia 2.28 (2.12–2.28), tarsus I–II 0.09 (0.09–0.11), 0.16 (0.14–0.16). Forefemur width 0.42 (0.39–0.42).

Foreleg: trochanter with 4–6 long setae on ventral region. Femur dorsally with two broad black stripes, one on anterior margin and another about one fifth from posterior margin, both confluent near apex ( Fig. 1A ); ventrally without prominent stripe, apically margined with piceous hue. Flexor side of femur with 9–11 setose spines, apex with three minute spines in addition to fringe of setae. Apex of tibia angularly produced on flexor side, with prominent spine subapically, with few erect setae; anterior apical margin fringed with several procumbent setae.

First tarsal segment basally with few procumbent hairs at anterior margin, with evenly distributed erect setae continuing to subapex of second tarsal segment; apex of second tarsal segment with three long setae on outer margin. Claws prominent. Middle leg: ventral region of trochanter with two to five denticles; posterior margin of femur from subbasal to beyond middle with short, curved, stout, evenly distributed spines; lower apical margin of femur with three long outwardly curved setae, apex with seven stout spines and fringed with long hairs; posterior margin of tibia fringed with long setae except base, maximum hair length 0.36 (0.32–0.36); first tarsal segment at base of inner margin with minute, apically curved hairs, second tarsal segment apically with one minute seta; claws absent. Hind leg: hind trochanter at posteroventral region with one to three thin short brown spines; femur at base of inner margin with three thin erect hairs; apex of femur with few stout spines; tibia and first tarsal segment without characteristic setae; separation between first and second tarsal segments distinct; second tarsal segment with one long and one short seta; claws absent.

Abdomen: dorsal length 2.28 (2.24–2.70); abdominal venter densely clothed with silvery white hairs; anterior margin of tergite I distinctly convex and posterior margin distinctly concave; separation between tergites I and II distinct; lengths of tergites I–IX, 0.26, 0.16, 0.12, 0.14, 0.16, 0.24, 0.62, 0.36, 0.23, combined length of tergites I–VII 1.69 (1.63–1.79); posterior margin of tergite VII straight to slightly convex; posterior margin of sternum VII straight to widely concave, connexivum angularly produced posteriorly ( Figs. 1A, E ); anterior region of sternum VIII with transverse depression; lengths of sternites II–VIII, 0.11, 0.12, 0.14, 0.16, 0.20, 0.28, 0.44, combined length of sternites II–VII 1.02. Proctiger (= suranal plate) very broad at base, suddenly narrowed beyond midlength to short posterior lobe, clothed with dense hairs ( Fig. 1J ). Pygophore with W-shaped median notch at base, its apical part produced into tongue-like lobe, clothed with minute hairs, posterolateral region of basal part blunt in lateral view ( Fig. 1H ), pygophore length 0.97, width 0.59 (measured after dissection). Paramere basally stout, curved before middle, outer margin beyond middle curved, apical part with pilosity, tip blunt and slightly bent to middle ( Fig. 1D ); paramere visible externally at abdominal tip ( Figs. 1A, E ). Endosoma: dorsal sclerite deeply split anteriorly and basally; formed of right and left sclerites; right dorsal sclerite reaching endosomal base, missing below; apex of dorsal sclerite forming C-shaped lobes, with outer lobe short and stout and inner lobe elongated and tip slightly inwardly bent in lateral view; left dorsal sclerite curved basally and fused with ventral sclerite; ventral sclerite broad, long, curved upward, beyond middle gradually tapered, subapex outwardly bent and reaching near anterior edge of dorsal and apical sclerites; ventral sclerites underlined by conjuctivum to subapex; basal region of lateral sclerites less sclerotised; outer margin of lateral sclerites emarginated and apex angulated; saddle-shaped apical sclerite placed between apex of dorsal and ventral sclerites, its lower margin concave, its outer margin straight; paired ovate membranous lobes with two to three vein-like dark lines, placed at apical part of endosoma ( Figs. 1K, L ).

Apterous female (paratypes). ( Figs. 1B, C, F, G, M ). Similar to holotype, with following exceptions (one female measured; range of all four specimens given in parentheses for some characters). Body length 6.97 (6.43–7.10), width at mesoacetabula 2.47 (2.13–2.50), head length 0.93, width at eyes 1.16, dorsal minimum width between eyes 0.41, eye length 0.55, eye width 0.30, antennal segments I–IV 2.73 (2.45–2.83), 0.77 (0.68–0.77), 0.84 (0.71–0.84), 0.73 (0.67–0.74); pronotal length 0.64 (0.56–0.64), pronotal width 1.15, posterior margin of pronotum almost straight, mesonotal length 1.99 (1.89–2.01), mesosternal length 3.01, median yellowish brown hue intruded into darker portion from lower region wider than in male; metanotal length (measured along midline upto tip of tubercle) 0.89 (0.85–0.91); metanotal tubercle well developed, erect, blunt, reaching posterior margin of abdominal tergite I, length 0.22 (measured at lateral region); metasternal length 0.25; combined length of mesonotum and metanotum 2.88 (2.72–2.91).

Legs. Lengths of leg segments: Foreleg, femur 2.65 (2.62–2.79), tibia 2.15 (2.15–2.26), tarsus I–II 0.86 (0.85–0.96), 0.64 (0.64–0.71); mid leg, femur 8.56 (7.63–8.56), tibia 4.56 (4.44–4.56), tarsus I–II 1.75 (1.64–1.75), 0.39 (0.36–0.39); hind leg, femur 7.93 (7.11–7.93), tibia 2.35 (2.23–2.35), tarsus I–II 0.10 (0.10–0.12), 0.17 (0.15–0.17). Forefemur width 0.28 (0.28–0.31). Length of hair fringe on mid tibia 0.38 (0.31–0.41); dorsal abdominal length 2.36 (2.28–2.44) (measured from tip of metanotal tubercle to tip of abdomen); lengths of tergites I–IX, 0.22 (maximum length of tergite I), 0.30, 0.22, 0.20, 0.26, 0.49, 0.45, 0.11, 0.31, combined length of tergites II–VI 1.47 (1.26–1.47), anterior margin of abdominal tergite II convex; lengths of sternites II–VII, 0.13, 0.16, 0.20, 0.27, 0.42, 0.79, combined length of sternites V–VI 0.69; posterior margin of sternum VII straight ( Fig. 1G ); anterior width of sternum VII 1.37, posterior width of sternum VII 0.76; connexival segment VI with long, tubular, yellowish brown process clothed with numerous short hairs; connexival process length, left 0.87, right 0.89 (measured along inner margin); connexival process surpassing abdominal tip, except in one specimen reaching abdominal tip; genital segments, gonapophyses processes rarely exposed (except for one female gonapophyses fully retracted into abdominal segment VII); posterior margin of tergite VI straight, tergite VII convex, VIII almost straight ( Figs. 1B, F ); proctiger (= segment IX) square to cylindrical ( Fig. 1M ); gonapophyses with brown sclerotised stripes prominent in lateral aspect; first gonapophysis (G-I) with several long setae basoventrally on both sides and with numerous medium-sized setae dispersed throughout ventral region; apically with a thorn-like blunt process, length of process I (GP-I) 0.14; distal region of second gonapophysis (G-II) clothed with setae, posterior margin with one pair of thorn-like blunt process, between two process at middle with small sclerite on second gonapophysis, length of gonapophysis process II (GP-II) 0.15, GP-II stouter than GP-I, below GP-II; apex of gonapophysis II with a pair of small sclerites, fringed with short setae on outer margin, inner margin emarginated, length of sclerite on apex of second gonapophysis 0.04; sclerites and processes on gonapophysis dark brown except tip of processes less sclerotised ( Fig. 1M ).

Distribution. Presently known from Jalpaiguri District, West Bengal, India ( Fig. 3 ).

Comparative notes. See under comparative notes of P. expositus .

Figures

FIGURES 1 A – M. Pleciobates bengalensis Jehamalar, Basu and Zettel, new species (A, D, E, H – L: male; B, C, F, G, M: female): A and B, dorsal view; C, metanotum and abdomen, lateral view showing metanotal tubercle; D, left paramere, lateral view; E, abdominal segment VIII and genitalia, ventral view; F, abdominal tip, dorsal view showing connexival process, tergites VI – VIII, and proctiger; G, abdominal tip, ventral view; H, genital capsule, lateral view; I, pygophore, ventral view; J, proctiger, dorsal view; K, endosoma, dorsal view; L, endosoma, lateral view showing sclerites; M, gonapophyses and proctiger, lateral view (as—apical sclerite; ct—conjunctivum; ds—dorsal sclerite; G-I—first gonapophysis; G-II—second gonapophysis; GP-I—process of first gonapophysis; GP-II—process of second gonapophysis; ls—lateral sclerite; ml—membranous lobe; pa—paramere; pr—proctiger; py—pygophore; sd—seminal duct; sl—sclerite; vp—ventral projection; vs—ventral sclerite).

FIGURES 3 A – C. Distribution of new species of Pleciobates. A, India; B, marked area denoting Assam and West Bengal in Northeast India; C, records of Pleciobates bengalensis Jehamalar, Basu and Zettel, new species in Jalpaiguri, West Bengal (triangles) and of Pleciobates expositus Jehamalar, Chandra and Zettel, new species in Dhubri, Assam (circles).