Nososticta nicobarica, Chandra, 2017

Chandra, Kailash, 2017, Nososticta nicobarica sp. nov. (Odonata: Platycnemididae: Disparoneurinae) from Great Nicobar Island, India, Zootaxa 4311 (3), pp. 426-434 : 427-434

Nososticta nicobarica sp. nov.

Holotype. Reg. No. ZSI-ANRC-T-4418; 1 ♂, Great Nicobar Island , Gandhi Nagar , 30 km North South road, near stream in tropical forest (06° 50'.215'' N, 093° 53'.381'' E; 90 m asl), 11.ii.2016, S. Rajeshkumar leg. Paratypes: Reg. No. ZSI-ANRC-T-4419, 1 ♂, 1 ♀, tropical rain forest stream nearby Old Cingen village, Galathea (06° 49'.361'' N, 093° 51'.460'' E), 14.ii.2016; Reg. No. ZSI-ANRC-T-4420, 3 ♂, GNBR (Great Nicobar Biosphere Reserve), near check post at hanging bridge (06° 58'.528'' N, 093° 51'.514'' E, 96 m asl), 18.ii.2016, Great Nicobar Island, S. Rajeshkumar leg.

Etymology. The specific epithet is derived from the name of the locality ‘ Great Nicobar’ where the type specimens were collected.

Description of holotype

( Figs. 1 A; 2 A–H; 4 A, C, D)

Head. Labium, labrum, mandible, gena and anteclypeus black; postclypeus pale blue; anterior frons on both sides of clypeus with pale blue bar; frons and vertex deep black except near lateral ocellus with small pale orange patch; antenna, antennal sockets and following segments black; rear of head black.

Thorax. Pronotum black with two pale yellow-orange patches dorsolaterally on anterior and median lobe; posterior lobe black with small yellow-orange spot laterally. Synthorax black with narrow yellowish orange antehumeral patches covering ½ of width and ⅔ of length of mesepisternum; anterior and posterior edges of antehumeral patch blunt and smoothly curved; mesepimeron black without stripe; metepisternum possess broad yellowish orange patch curving down anterior to metastigma; metepimeron with a small yellowish orange patch less than ½ of metepimeron almost quadrangle in shape in the posterior part; anterior part of metepimeron almost black without any spot; ventral side of synthorax washed pale yellow; legs black; coxae and trochanter washed pale yellow; femora, tibia, tarsi and claws brown; spines blackish.

Wings. Membrane hyaline; veins black; pterostigma dark brown, overlying one cell; Px 18-16/18-16; CuP reaching the wing margin at about half a cell following the discoidal cell in fore wing and nearly two cells in hindwing.

Abdomen. S1–6 mostly brownish black, pale ventrally; S1 and S2 pale yellowish orange irregular spots laterally; S4, S5 and S6 much longer than other segments; S7–10 black, broader than rest of the segments; pale blue patch dorsally covering almost all of S8 while slightly constricted at posterior mid-dorsal keel of S9; S8–S9 pale blue patch extending laterally; anterior dorsum of S10 has restricted transverse pale blue patch without extending laterally.

Anal appendages. Cercus brownish to black, longer than S10, triangular dorsally with acute apex deeply bifurcate and distinctly curved downward; acute tooth on inner side reaching upper portion of paraprocts; paraprocts brownish to black, longer than cercus; almost straight with blunt apex slightly curved upward; pale inner margin with small and somewhat rectangular hook; paraprocts in dorsal view concavely rounded at the apical quarter and earlobe shaped.

Measurements (in mm). Total length (with appendages) 43.5; abdomen length (without appendages) 36.0; hindwing 22.0; Pt in forewing 0.9.

Variations in paratype males. Head. As in holotype

Thorax. As in holotype but blue in life and pale in apparently immature specimens after preservation.

Wings. Generally as in holotype; variations were established in the number of Px ranging from 15–18 in hindwing and CuP reaching wing margin at about 1½ cells distally of the quadrangle in 1 ♂ paratype specimen; however, other 2 ♂ paratypes are same as holotype.

Abdomen. Pale blue pattern on dorsum of S9 covered completely without leaving any notch at posterior middorsal keel in 2 ♂ paratypes.

Measurements (in mm). Total length (with appendages) 40.6–43.6; abdomen length (without appendages) 34.5–36.7; hindwing 20.8–23.1; Pt in forewing 0.9–1.0.

Description of female

( Figs. 3 A–G; 4 B, E–I)

Head. As in male.

Thorax. The anterior lobe of pronotum divergent with a paired horn-like processes, nearly equal the height of the prothorax measured from the crest of the median lobe; in lateral view appearing slender, bending slightly posteriorly over median lobe; in dorsal view broader at base then narrow, blunt apex; posterior lobe with two short club-shaped processes; pronotum with the anterior lobe dark brown to black with pale blue patch dorsolaterally, covering at least half of the long horn-like processes, median lobe black with large pale blue patch laterally almost spherical and posterior lobe black with small pale blue patch dorsolaterally, not connected to median lobe; synthorax as in male but with pale blue antehumeral patches; broad pale blue stripe on posterior metepisternum narrowed anterior of metastigma slightly longer than male; ventral side of synthorax same as male; legs are similar to male.

Wings. As in male but Pt dull brown to black; Px 16-16/16-16; incomplete in hindwing; length of hindwing smaller than male; CuP reaching the wing margin at about half a cell following the discoidal cell in forewing, but 1½ cell following discoidal cell in hindwing.

Abdomen. S1–S7 as in male; S8 with pale bluish anterior patch dorsally covering up to ¼ of segment, extending laterally in the same segment; S9 and S10 black without any patches; dark reddish brown ovipositor reaching beyond end of S10; a pair of black styli at caudal end; valves largely brown but black dorsally in apical half; approximately 38 sharp teeth along ventral margin.

Measurements (in mm). Total length (with appendages) 40.1; abdomen length (without appendages) 32.6; hindwing 21.0; Pt in forewing 0.9.

App.-appendages; HW-hindwing; mm-millimetre; Nos.-Numbers; Pt.-Pterostigma; Px-Post nodal cross veins; Ssegment [Sources: Lieftinck 1936 & 1953; Selys 1886; Förster 1896; Seehausen & Theischinger 2017]

Differential diagnosis. As in all species of the Sundaic region and the Lesser Sundas, the vein CuP in hindwing of N. nicobarica sp. nov. is long, reaching one or more entire cell following discoidal cell. This separates it from all Papuan and Australian species where CuP is shorter, commonly reaching less than one entire cell past the discoidal cell. The shape of the male anal appendages is much different from all Sundaic and Lesser Sunda species. Cerci with acute apex and distinctly curved downward rather than straight or without curving downward. Paraprocts almost straight with blunt apex slightly curved upward and the inner margin with small, somewhat rectangular hook is clearly distinct from all species of Lesser Sundas. Also the shapes of female pronotum lobes are quite different from all Sundaic and Lesser Sunda species. The anterior lobe of pronotum divergent with two long horn-like processes in N. nicobarica sp. nov. and is much longer than all Sundaic and Lesser Sunda species. The posterior lobe short, paired club-shaped processes unlike long horn-like processes as in all Sundaic and Lesser Sunda species. This new species also differs on the basis of colour pattern on synthorax and terminal segments (S8–10) of abdomen from N. diadesma , N. emphyla and N. selysi . Based on studied characters, two colour forms (yellowish orange and pale blue) of ante-humeral stripes were found in male. Apparently the adult male has yellowish orange thoracic stripes while they are pale blue in immature males; the yellowish orange pattern on prothorax is somewhat similar to N. impercepta and N. insignis . The antehumeral patch differs from N. insignis (covering half length and width of mesepisternum) by covering ½ of width and ¾ of length of mesepisternum. In N. impercepta the antehumaral patch narrows anteriorly but is smooth edged on both sides in N. nicobarica sp. nov. Further differences are the metepimeral stripe which is narrow without any split in N. nicobarica sp. nov. and terminal segments of the abdomen are pale blue and cover almost entire S8–9 ( Fig. 4 ). In female, S8 with a pale bluish anterior patch dorsally covering up to ¼ of segment in N. nicobarica sp. nov. ( Fig. 4 ), while two semicircular yellow patches anteriorly and transverse stripe posteriorly are present in N. impercepta . A detailed morphological comparison among all closely related species from Lesser Sundas is provided ( Table 1).

Habitat and Ecology. This species was common along small streams, particularly near waterfalls in the interior of the tropical rainforest where the adults perched in sunny patches on thick vegetation of endemic tree ferns ( Sphaeropteris albosetacea (Bedd.) R.M. Tryon ) ( Fig. 5 ).

Distribution. Nososticta nicobarica sp. nov. is to date known only from the type locality and was found only in tropical rainforest areas. After an extensive literature survey, it is presumed to be endemic to Great Nicobar Island.

Discussion

It is clear that N. nicobarica sp. nov. is distinct from any known species. Comparisons are to somewhat limited as in the genus Nososticta females are mostly undescribed. Therefore the significance of the highly unusual female thoracic armature is not entirely. It is however probable that the newly described species is most closely related to species found in Lesser Sundas in Southeast Asia none of which is conspecific with Papuan or Australian species.

Figures

FIGURE 1. Nososticta nicobarica sp. nov, in life: A. Adult ♂; B. Immature ♂; C. Mating pair.

FIGURE 2. Nososticta nicobarica sp. nov. ♂ A, B. Head and thorax: A (lateral view) B. (dorsal view); C. Frontal view of head; D. Wings; E. Secondary genitalia (ventral view); F – H. S 7 – 10 with anal appendages: F. Paraprocts (ventral view); G. Dorsal view of cerci; H. lateral view. All images (except G – paratype male) are of the holotype.

FIGURE 3. Nososticta nicobarica sp. nov. ♀ A. Head (dorsal view) and thorax (lateral view); B. Head and thorax (dorsal view); C. Frontal view of head; D. Wings; E – G. S 7 – S 10 (E. dorsal view; F. ventral view; G. lateral view).

FIGURE 4. Synthorax of Nososticta nicobarica sp. nov. (A. male (holotype); B. female); S 8 – 10 of the abdomen dorsal and lateral view (C & D-male (holotype); E & F- female); Pronotum of female (G. lateral view; H. dorsal view (without colour pattern); I. oblique view from left). Illustrations: S. Rajeshkumar.

FIGURE 5. Habitat of Nososticta nicobarica sp. nov. at type locality Great Nicobar Island.