Nesocordulia, McLachlan, 1882

Bernard, Rafał, Daraż, Bogusław, Ravelomanana, Andrianjaka & Dijkstra, Klaas-Douwe B., 2025, Six new species of Nesocordulia McLachlan, 1882 reveal an insular evolutionary radiation of dragonflies on Madagascar (Odonata: Anisoptera: Libelluloidea), Zootaxa 5660 (2), pp. 151-193 : 153-154

Genus Nesocordulia

Nesocordulia McLachlan, 1882 —Knifetails

Etymology. From the Ancient Greek νήΣΟΣ (nêsos)— island ( McLachlan 1882) and Cordulia —the feminine form of Latinised adjective derived from Greek ΚΟΡδύλη —club or cudgel ( Fliedner & Endersby 2019).

Description. Rather small to medium-sized dragonflies, total length 41–60 mm, Hw 28–41 mm. Arched posterior border of eyes. All male tibiae with whitish tibial keels, contrasting with the dark background. Male with auricles on S2. Abdomen clubbed, S7–10 being expanded (with S8 the widest), although less so in females. Dorsum of male S10 with spine- or keel-like longitudinal tergal process, which ends distally in an acute point. Anal triangle of male Hw with 2 cells (large basal and small apical). Fw with 1 Cux, Hw with 2. Anal loop long and sack-shaped, ending well distal of triangle, with 12–20 (mostly 13–18) cells in males, and 15–22 (mostly 15–20) in females.

Colouration generally dark (partly with metallic reflections) with yellow patterning. Metallic reflections found on synthorax and head, but not on abdomen, and are mostly green, but also blue, violet, bronze, copper and golden. On head these are present regularly on vertex, frons and sides of postclypeus. A yellow centre of clypeus in all but one species. Labrum most frequently dark, labium pale or two-toned. Eyes when alive are purplish brown anterodorsally and blue posteroventrally, sometimes with bright green in between. On synthorax, metallic reflections occupy various areas, from three distinct stripes to almost whole strongly melanised surface. On mesepisternum, a metallic stripe with a non-metallic brown area in various proportions: regularly covers upper parts along the middorsal carina, but in some cases almost the whole surface except the brown anterolateral corner (sometimes with a blurred yellow spot). On mesepimeron, metallic reflections occur especially in its anterior parts, where green is frequently extended down with copper. On metepisternum, variably extensive metallic reflections encircle a yellow spot. On metepimeron, a metallic green stripe covers its anterior region. On synthoracic sides of all but one species, diagnostic pattern of 2–5 pure yellow spots. Poststernum pale (in colour of thoracic spots) or dark (in colour of thoracic background). Legs mostly dark, brown to black, with increasing amounts of yellow (or reddish brown in two reddish brown species) from hindlegs to forelegs, usually found on: (a) coxa in hindlegs, (b) coxa and trochanter in midlegs, and (c) coxa, trochanter and part of femur in forelegs, where spread from its base to two thirds of the length. Except reddish brown species, paired yellow pattern on black abdomen. In most species, S2 on each side with: (a) two yellow spots laterodorsally, and (b) a long lateroventral spot or two smaller spots, rearwards entering at least basally into the genital lobe. On each side of S3–6, the laterodorsal pattern including anterior and posterior stripes, the former frequently on all segments (in some cases reduced to S3–5 or S3–4) while the latter frequently limited to S3 and S4 only. In females, the yellow pattern is more complete. The anterior and posterior stripes differ in their form (best visible on S3): the former has its dorsal margin concave and the latter convex. The S3–6 pattern is interspecifically variable. In many species, paired basal laterodorsal yellow spots on S7, most frequently forming a continuous or broken ring or half-ring. Along the ventral carina of S3–6, pale yellowish lines, in some cases broadened anteriorly.

Descriptions of new species