Oligoaeschna sirindhornae, Ngiam & Orr, 2017

Ngiam, Robin W. J. & Orr, Albert G., 2017, Oligoaeschna sirindhornae sp. nov., a new dragonfly species from Thailand (Odonata: Anisoptera: Aeshnidae), Zootaxa 4353 (1), pp. 195-200 : 195-199

Oligoaeschna sirindhornae sp. nov. ( Figs 1–3 )

Holotype. ♂, Thailand, Nakhon Ratchasima Province, Sakaerat Silvicultural Research Station, ‘ Khao Sunt’ forest , 14.49467N 101.87100E, alt. 606m a.s.l., 27 vi 2014, R. W. J. Ngiam leg. To be deposited at Lee Kong Chian Natural History Museum (LKCNHM), Singapore .

Etymology. We humbly dedicate this species to Her Royal Highness, The Princess Maha Chakri Sirindhorn of Thailand, in recognition of her continuing support of nature conservation and as a mark of personal admiration by the authors. The specific epithet sirindhornae is a noun in the genitive case.

Description of holotype. Head. Labium almost entirely brown and broad basally; labial palps generally brown and slightly darkened apically. Labrum dark brown, its lower part black laterally. Mandibles black. Anteclypeus dark brown. Postclypeus dark brown with the upper half much darker. Frons entirely black except for a slight yellowish horizontal stripe on both sides. In dorsal view frons moderately produced with corners and anterior margin rounded ( Fig. 1 ); margin with dense fringe of moderately long setae. Antennae black. Vertex shiny yellow, rectangular with rounded corners. Ocelli pale yellowish. Occiput entirely black except for two pale yellowish horizontal stripes, one on each sides of lower half occiput the occiput lower half. Eyes typical of the genus; dark green in life.

Thorax. Prothorax almost entirely black. Synthorax black with greenish dorsal stripes angled inwards on the mesepisternum, and transverse greenish stripes below the pre-alar ridge. Greenish spots present on the mesoscutum, mesopostnotum, metascutum, metascutellum, and humeral and axillary sclerites of all wings. Laterally ( Fig. 2a ), greenish stripe on the mesepimeron; metepimeron almost entirely green. Legs black.

Wings ( Fig. 3 ). Fw with 17 antenodal cross-veins (Anx) and nine postnodal cross-veins (Pnx). Pterostigma (Pt) dark, overlaying three cells. Two cubital cross veins (Cux). In Hw, 13 antenodal and 11 postnodal cross-veins. Pt dark, overlaying three and a half cells. Two Cux. Three cells in anal triangle and three cells in anal loop. Three cells in the triangle in both wings, membranule in both wings small, dark brown.

Abdomen ( Fig. 1 ). Overall broad at base, moderately constricted at S3 and thereafter moderately spindle shaped. Black with bright green or yellowish markings. S1 black with thick tuft of setae dorsally; dorsum S2 with rounded green spot anteriorly, paired transverse green dashes behind transverse carina and pair of smaller spots at base. Dorsal setae sparse. Laterally, large irregular green to yellowish antero-ventral spot extending to ventral side of auricle and smaller green medio-apical spot. Auricles pale greenish-yellow, more strongly yellow above. S3 maximally constricted at one third of its length from base; small paired green spots medially and paired transverse green spots posteriorly. Dorsal pattern on S4 similar to S3. S5 to S9 with only paired transverse green spots apically, these decreasing in size from S5 to S9. S10 entirely black.

Anal appendages ( Fig. 2b–c ). Black. Cerci in dorsal view ( Fig. 2b ) long and robust; nearly twice length of S10; with slightly sinuous outline, medially kinked in outer margin, distal half approximately an elongate oval shape with strong longitudinal ridge. In lateral view ( Fig. 2c ) cerci rather angulate, broad anteriorly narrowing maximally at two-fifths length from base; small pointed sub-basal process present ventrally; apical three-fifths forming a narrow approximately triangular shape with vertices on the midpoint of dorsum at the corner of a ventral flange and apically; apex slightly truncated obliquely. Epiproct about half length of cerci, narrow basally and narrowing slightly further towards apex which expands narrowly to form a moderately excavated fork; in lateral view, curving smoothly upward with terminal re-curved spine.

Accessory genitalia. With spine of anterior lamina small; anterior hamule slightly serrated with small spines. Penis ( Fig. 2d ) strongly curved, basal joint of (seminal vesicle) thick and with fleshy lobe. Second joint of penis as thick as posterior of basal joint, heavily folded, fleshy lobes large, heavily folded, terminating in a sharp pointed tip, no flagellum.

Measurements [mm]. Hw 40, abdomen without anal appendages 42, cerci ca 4.1, epiproct ca 2.1

Diagnosis. This new species distinctly differs from all other congeners by the unique shape of its cerci in both dorsal and lateral view. The nearest relatives geographically are known from Peninsular Malaysia. These are Oligoaeschna amata (Foerster, 1903) and Oligoaeschna foliacea Lieftinck, 1968 , in which the cerci are very dissimilar from this species (see the illustrations in Orr 2005).

Habitat. Oligoaeschna sirindhornae sp. nov. was found in mixed dipterocarp forest, at a shallow stream with small boulders at the bottom of a ravine by the edge of a silviculture plantation ( Fig. 4 ). It was collected in late June when the stream was dry during a period of low rainfall. The specimen was caught when it was flushed from the undergrowth and rested among a thicket of palms.

Figures

FIGURE 1. Oligaeschna sirindhorni sp. nov. holotype,habitus.

FIGURE 2. Oligaeschna sirindhornae sp. nov. holotype: a. synthorax lateral view; b. anal appendages, dorsal view; c anal appendages, lateralview; d. detail of penisshowing absenceof flagellum on terminal segment.

FIGURE 3. Oligaeschna sirindhornae sp.nov. holotype:wing venation.

FIGURE 4. Habitatwhere the holotype of O.sirindhornae sp. nov. was captured.