Megalestes gyalsey Gyeltshen, Kalkman & Orr, 2017, sp. nov.

Megalestes gyalsey sp. nov.

(Figs 1–4)

Material examined. Holotype ♂. Bhutan, Trongsa District, along Wangdue – Trongsa Highway, (27.457N, 90.368E; 2450 m a.s.l.), 17.x.2015, leg. T. Gyeltshen & V.J. Kalkman. The type is stored at the collection of the National Biodiversity Centre, Bhutan (NBCB-00252). DNA material is stored at the collection of the RMNH (RMNH.5015087). The species was present at a small brook running through deciduous forest and was caught at a small open area where the brook reached the road verge (Fig. 2).

Etymology. The specific epithet gyalsey, is a noun in apposition. The species is named in honour of His Royal Highness Crown Prince of Bhutan, The Gyalsey, Jigme Namgyel Wangchuck, on the occasion of his first birthday.

Description of holotype male. Head: Labium pale yellow. Head shining metallic coppery green with pale yellow markings on anterior corners of labrum, mandibles except upper anterior corner, and genae directly adjacent to mandibles. Antennae black, ocelli pale. Posterior part of head, behind ocelli, matt greyish black.

Thorax: Pronotum with central two-thirds of both anterior and posterior lobe yellow, remainder metallic greenish to black. Posterior lobe normally developed, lacking specialised processes or excavations. Side of prothorax metallic greenish to black with lower margin adjacent to coxa a U-shaped yellow area. Synthorax intense metallic green on dorsum and sides, covering entire mesepimeron and most of mesinfraepisternum apart from a small yellow mark at posteroventral corner. Metepisternum and metepimeron largely yellow but with broad metallic green band along suture reaching to half breadth of spiracle and continued as dull black in most of anterior part of metainfraepisternum (Fig. 3). Coxae and trochanters of first two pairs of legs largely yellow, coxae and trochanters of third pair of legs yellow with large black patch as shown in Fig. 3. Remainder of legs black.

Wings: Membrane tinted light brownish amber, venation dark brown to black; pterostigma dark brown to black, narrow, elongate and slightly expanded in middle, extending over 3–4 cells. Wing base petiolated to about halfway between Ax1 and Ax2. Right Fw has 3 Ax, all other wings have 2 Ax. Px 18 in the Fw; 15–17 in Hw.

Abdomen:Largely dark with slight metallic green sheen, darker posteriorly; S1 and especially S2 bright metallic green dorsally and laterally. Ventral half of side of S1 and ventral third of S2 pale yellow. Dorsum of segments 9–10 pale pruinose blue. Anal appendages black and shaped as in Fig 4a–b. Cerci longer than S10, basally broad with a short, blunt, posteriorly directed finger-like process on the interior, remainder of interior margin smooth and lacking spines. In lateral view apical third bent downward and apex bifurcated with rounded upper process and slightly longer narrow acute lower process. Paraprocts a little over half as long as cerci, each with broad base, especially distinctive in lateral view, narrowing halfway and with apical half forming a strong, narrow, apically pointed finger-like process; tips slightly divergent in dorsal view.

Measurements (mm): total length 58; abdomen 47.5, Fw 36; Hw 35.

Female Unknown.

Differential diagnosis. Megalestes and Sinolestes are the only damselfly genera in mainland Asia with a pterostigma that is at least twice as long as broad, a metallic green colouration and a total length of over 50 mm. The only genus matching the first two characters is Lestes, but the species of that genus are smaller and have R4 and Ir3 originating well proximal of the subnodus (at the subnodus in Megalestes and Sinolestes). Megalestes gyalsey can best separated from all other species of Megalestes and Sinolestes based on its anal appendages: the paraprocts are slightly over half the length of the cerci and have a relatively simple structure with the apical half consisting of a strong apically pointed gently curved finger-like process and lacking small upcurved spines. Figure 4c–f shows the anal appendages of Megalestes major and M. irma, the two other species of the genus known from Bhutan.