Gynacantha vanuatua Theischinger, Marinov & Bybee, 2020

Theischinger, Gunther, Marinov, Milen, Bybee, Seth, Jensen, Colin, Theuerkauf, Jörn & Rashni, Bindiya, 2020, The genus Gynacantha Rambur, 1842 in the South Pacific (Odonata: Anisoptera: Aeshnidae), Zootaxa 4778 (1), pp. 171-195 : 177-181

Gynacantha vanuatua Theischinger, Marinov & Bybee , sp. nov.

( Figs 6 , 15, 16 , 24 , 34c, 34d , 36m, 36q )

Holotype: ♂ (BYUIC-2020-01, MLBM), Republic of Vanuatu, Malekula Island , 16.2475°S, 167.6168°E, 09 May 2019, S. Bybee & C. Jensen leg.

Paratype: 1 ♂ (BYUIC-2020-02, MLBM), Republic of Vanuatu, Malekula Island , “Giving Stream” 16.1650°S, 167.4925°E, 07 May 2019, S. Bybee & C. Jensen leg.

Etymology. The name refers to the larger type locality; by adding an ‘a’ it forms an adjective conforming in gender and ending to the generic name.

Description of holotype

Head. Labium, bases of mandibles and labrum pale yellow; anteclypeus, postclypeus and antefrons dark green with slight yellow marks, on postclypeus appearing brownish; postfrons with a pale brown T-shaped mark on top contrasting with the yellow ground area, apical transverse bar of the T-shape laterally fading into dark green toward the anterior part of the frons; scape and pedicel dark yellow, on the pedicel slightly brighter with apical dark spot, flagellum pale brown; vertex brown; occipital triangle yellow; postgenae pale yellow with dark red transverse bar just behind the occipital triangle. Eyes pale brownish grey (by way of preservation).

Thorax. Prothorax pale yellow with a faint brown area on the dorsum of the middle lobe. Synthorax overall pale green merging into pale yellow, towards ventral portion yellow deepens in intensity along the sutures and bases of coxae; faint brown areas developed along the side of the heavily ridged dorsal carina, and dorsal ends of meso- and metapleural sutures; metaspiracle ring black with slight dark red reflection; another dark spot at the anterior end of the metapoststernum. Legs: coxae pale yellow with brighter yellow patches on the lateral surfaces, all femora bright with dark apical areas, colour intensifying from front (yellow-green) toward hind (dark orange) legs, all tibiae bright yellow, claws almost uniformly yellow with slightly reddish tips.

Wings. Membrane hyaline with yellow tinged areas at the base, most intensive between Sc and R+M; wing triangles with six cells (five on right Hw); Arc at the level of Ax3; no double cells in proximal half between CuP and A1 of Hw; anal triangle 3-celled; anal loop with 12 cells; nodal index 19–24 / 25– 20 in Fw and 24–18 / 21– 20 in Hw.

Abdomen. Ground colour brown—paler in anterior portion of segments and slightly darkening posteriorly, uniformly dark on the dorsum of S9; dorsum of S2 with a pattern of green and yellow markings as in Fig. 24 , green on the antero-ventral areas of S3 too; S3–8 with yellow spots and streaks as follows: paired spots at the dorso-posterior ends of the segments (very obscured on S8) sitting close together, separated by the dark brown segmental carina, yellow lines alongside posterior edge of the intersegmental transverse carinae, thin lines ascending from the venter along the anterior edges of the segments ending just dorsal of the lateral mid-section of the segments. Auricles of S2 with six spines on right and five on the left where two spines are doubled. Genital fossa with a subtriangular arrangement of 10–12 denticles restricted at the both sides posterior of the penis sheath, 5–6 of these larger than the rest, no denticles anterior of bend in the genital fossa; spines of anterior lamina weakly arched inward. Constriction of S3 0.4 times the posterior width of the segment.

Anal appendages. Superiors straight, parallel outer edges for almost the whole length, slightly incurved before the end which bears an outward directed sharp tip; dark orange-yellow at the bases which darkens to brown towards the tips; heavily setulose with black hairs; longitudinal carina developed alongside the outer edge with a grove developed for more than 2/3 of the length of the appendage from the base, inner carina beginning about the midpoint of the appendage and continuing to the tip where it meets the outer carina enclosing a depressed dilated apical zone. Inferior almost exactly 1/3 length of the superiors, brown at the base and very tip, pale yellow for the rest.

Measurements (in mm). Abdomen (including appendages) 55.0, appendage 7.0, HW 47.0.

Variation in the paratype. Identical to holotype in general habitus, structure and colouration. Variations in wing venation—13 cells in the anal loop of both wings; nodal index: 19–26 / 28– 21 in Fw, 22–21 / 19–23 in Hw, denticles on the auricles 7 on left and 6 on right.

Measurements (in mm). Abdomen (including appendages) 53.0, appendages 6.0, Hw 48.0.

Distribution. Only known from Malekula Island, Vanuatu.

Diagnostic characters: Postfrons with dark T-mark. Both Hw with space between CuP and A1 basally not expanded and without double cells in proximal half. Denticles along posterior portion of genital fossa rather formatted into a densely set subtriangular patch, no denticles present along anterior portion. Superior anal appendages straight with outer margin of approximately apical third very slightly convex and with apex rather widely curved posterolaterally into a moderately long point; inferior appendage almost exactly 1/3 as long as superiors, with lateral edges of basal portion convex and rather abruptly narrowing into narrowly trapezoidal apical portion.

Only species of Gynacantha known from the Republic of Vanuatu. Distinguished from all species of the G. rosenbergi Pacific group by (1) subtriangularly arranged group of denticles only along posterior part of genital fossa and absence of even an occasional denticle along the anterior part, (2) by the straight superior anal appendages with apex rather widely curved postero-laterally into a longer point and (3) by the longer inferior appendage.

Figures

FIGURE 24. Gynacantha vanuatua, male, Holotype; insert male: S2, ventral; anal appendages, dorsal.

FIGURE 34. Gynacantha sp. with superior anal appendages sharply pointed: (a) G. dobsoni from Australia; (b) G. dobsoni from New Caledonia, Lifou; (c, d) G. vanuatua; (e) G. vitiana; (f) G. koroana; (g) G. sp. cf stevensoni.

FIGURE 36. Key structures of males of Gynacantha species. (a, c, e) S2 and S3, ventral, (b, d, f) anal appendages, dorsal: (a, b) G. rosenbergi; (c, d) G. dobsoni; (e, f) G. apiaensis; (g, i) part of hindwing, (h, j) S2 and S3, dorsal: (g, h) G. amphora; (i, j) G. dobsoni; (k, l) head: (k) G. apiaensis; (l) G. cf. stevensoni; (m–p) genital fossa, (q–t) anal appendages: (m, q) G. vanuatua; (n, r) G. vitiana; (o, s) G. koroana; (p, t) G. sp. cf. stevensoni.

FIGURES 3–11. Gynacantha species, male S2, ventral (to show arrangement of denticles along genital fossa): (3) G. rosenbergi; (4) G. dobsoni; (5) G. amphora; (6) G. vanuatua; (7) G. vitiana; (8) G. koroana; (9) G. stevensoni; (10) Gynacantha cf stevensoni; (11) G. apiaensis.

FIGURES 12–21. Gynacantha species, male anal appendages dorsal (to show differences between width of S10 and length of superior anal appendages): (12) G. rosenbergi; (13) G. dobsoni; (14) G. amphora; (15, 16) G. vanuatua; (17) G. vitiana; (18) G. koroana; (19) G. stevensoni; (20) G. cf stevensoni; (21) G. apiaensis.