Vanuatubasis rhomboides, Saxton & Marinov & Bybee, 2022

Saxton, Natalie A., Marinov, Milen G. & Bybee, Seth M., 2022, Revision of Vanuatubasis Ober & Staniczek, 2009 (Odonata, Coenagrionidae), with description of seven new species, ZooKeys 1128, pp. 129-169 : 129

Vanuatubasis rhomboides sp. nov.

Figs 9 , 21H

Type material.

Holotype (1 ♀ NZAC). (NZAC04230978, New Zealand Arthropod Collection, Auckland, New Zealand), locality data: Republic of Vanuatu, Malekula Island, Stretch of Lakatchkach River flowing through Postanle Area (-16.1437, 167.4671 to -16.1474, 167.4649; 15-51 m a.s.l.): 17 May 2017; M. Marinov & S. Bybee leg.

Paratype (1 ♀ NZAC). NZAC04231074, Malekula Island, Litslits (-16.1435, 167.4671; 15 m a.s.l.): 07 May 2019, S. Bybee & G. Powell leg.

Description of holotype.

Head: Labium pale yellow, labrum, mandibles (except for the reddish tips), whole clypeus, frons and genae along the eyes up to the dorsal ends of the scapes, scapes citron yellow except for dark fuscous to dark reddish spots at the dorsal corners of the mandibles at the ends of the lateral proximal corners of the postclypeus plus lateral sides of labrum running down for almost the whole length to the anterior edge; pedicels brownish; flagella dark red; scape: pedicel 0.5; vertex black with slight dark red sheen with three yellow spots - two are horn-like expansions of the yellow on the postfrons into the dark vertex and the third is just in front of the median ocellus; rear part of the head yellow which is continuing up toward the occipital area and visible from the dorsum in a shape of two pear-like yellow areas on the postocular lobes and a small spot on the occipital bar; two roughly circular occipital spots formed by pale pruinescence; eyes orange yellow with pale fulvous areas on the dorsal part.

Thorax: Dark wide bar (slightly tapering towards posterior end) with slight reddish sheen passing on the dorsal part of pro- and pterothorax encompassing ~ 3/4 of the dorsal part of the mesostigmal plate and 1/2 of mesepisternum (faint pale line along the dorsal carina starting approximately midway and gradually becoming lighter towards the pre-alar area), at the posterior end the dark bar abruptly curves ventrally at a near 90° angle and joins the posterior end of mesopleural suture with a semicircular curvature; dark elongated spots with same color developed also as follows: two sitting on the dorsal edges of the meso- and metapleural sutures at their posterior ends and connecting to two dark shiny spots at the alar areas by a tiny bridge with the same color and a solid bar on the posterior edge of poststernum; legs almost entirely yellow save for darken areas on the inner surfaces of the front tibia in the proximal 2/3 and dorsal part of all femora occupying as follows: distal 1/2 of front femora, 9/10 of the distal part in the middle and hind legs, all dark areas with characteristic pale spots giving a barred-like appearance, pale spots on front femora weakly developed forming serrated outer edges; dark spots at the joints between femora and tibiae and distal tips of the last tarsal segments; claws orange with darker reddish tips; all the leg spines black; mesostigmal plate triangular in shape with dorsoposterior end enlarged and extruded into an auricle-like lobe, ventral side wide rounded and slightly elevated and separated from the thorax; hind lobe of the prothorax is triangular with two parallel carinae ventrally arising out from the lateral sides of the hind lobe and running posteriorly to the dorsal edge.

Wings: Hyaline; venation generally dark especially at the distal ends becoming paler towards the bases with pale spots at the nodus at both outer and inner sides; pterostigma with protruding posterior proximal end into a sharp angle which is dissimilar in both front and hind wings differing in the following: front wing smaller with central fuscous area outlined with pale yellow, hind wing larger with anterior end 2/3 of the length of posterior, bicolored with dark area continuing towards the sharp proximal end of the pterostigma and pale yellow anterior part; CuP slightly proximal to halfway between antenodals in front wings and halfway in hind wings sitting on the top CuP and AA distal at the point where the latter is leaving the wing edge; arculus at second antenodal in front wings and slightly distal to it in hind wings; discoidal cells dissimilar in shape - in front wings anterior side is ~ 1/3 of the posterior and in hind wings anterior side is more than ½ of posterior; two postdiscoidal cells before nodus; nodal index: 12/2-2/12 in front wings and 10/2-2/10; MA and MP very long reaching to surpassing the midway between nodus and pterostigmas, CuA surpassing the nodus and ends proximal to the midway between nodus and pterostigma.

Abdomen: Black dorsal area running from S1 to S8 continuing on the dorsal 1/2 of S9 where it descends on the lateral side of the segment outlining a wide circular beige spot on each side of the segment and joining the posterior end of the segment, dark area on the dorsum of S9 ends up at two round lobes, posterior dorsal 1/2 of S9 with a pale brownish bar, S10 with a dark area on the dorsum which is constricted at both lateral sides by the beige expansions from the lateral sides of the segment giving the dark area a roughly X-shape when viewed from the dorsum; dark area with dorsal invaginations forming lateral bulbous expansions at proximal ends on S2 and S3 and yellow bars continuing up almost meeting on the dorsum of S3-S5; ventral side of the abdomen yellow with slim dark lines on the ridges of the sternites 2-8, those lines faint on second segment occupying approximately mid-area and continuing more towards the anterior part of the segment, slightly skewed towards the anterior end on segments 3-5 and equidistant from both ends of the segments on 6-8; posterior end of the eight sternite lacking tooth; cerci fuscous with pale tips; ovipositor yellow surpassing the posterior end of S10 with the tip reaching just before the distal tips of the cerci, styli yellow at the extreme base and gradually darkening becoming deep dark red distally with very weak yellow lightening at the tips, styli surpassing the cerci.

Measurements (in mm): total length 35.5, abdomen 30.0, hind wing 22.5.

Diagnosis.

Vanuatubasis rhomboides has a mesostigmal plate with the dorso-posterior end raised as an auricle. This shape is found only in three other congeners: V. kapularum , V. nunggoli , and V. malekulana. The height of the auricle is less pronounced in the first two species, but V. malekulana has a similarly high auricle to V. rhomboides . The latter is distinguished by all other congeners by the rhomboidal shape of the pterostigmata which are characteristically bicolored in HW.

Variation.

Body overall green and predominantly yellow on the ventral side; dark area on the dorsum of S9-10 reduced. Measurements (in mm): total length, abdomen 30.0, hind wing 22.5.

Distribution.

Malekula, Vanuatu.

Etymology.

The name Vanuatubasis rhomboides is Latinized form of Greek ῥομβοειδής, - ής, - έϛ = like a rhombus, rhomboid, in reference to the shape of the pterostigmata {adjective}.

Notes.

This species is only known from female specimens as no males were able to be associated.

Figures

Figure 9. Vanuatubasis rhomboides Holotype (♀ NZAC) A dorsal thorax B lateral terminalia. Scale bars: 0.5 mm.

Figure 21. Female face and dorsal terminalia of A V. bidens B V. discontinua C V. evelynae D V. insularivorum E V. kapularum F V. malekulana G V. nunggoli H V. rhomboides I V. santoensis J V. xanthochroa.