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 : 184-185

Key to males of Nesocordulia

The key is to males only, as females are available for only half of the twelve species. Caution is advised, moreover, as for six of the species characters are based on single specimens.

1 Abdomen largely reddish brown, without distinct yellow markings. Cerci and epiproct reddish brown, similar to abdominal colouration. Wing membrane with brown markings at base. Branches of hamule separated by deep and wide gap, with posterior branch pressed against genital lobe. Venation dense; 15–16 Ax in Fw; row between cubital and anal veins in Hw with 5–8 cells doubled (to multiplied)................................................................................. 2

– Abdomen at least partly black with contrasting yellow markings. Cerci at least on tips white to yellowish, contrasting with darker abdomen, in some species epiproct paler too. At base, wing membrane hyaline or at most tinted with yellow. Branches of hamule, if recognisable, closely apposed, with only slight or, if deep, narrow incision between them. Venation more open; 10–13 Ax in Fw, rarely up to 15; single row of cells between cubital and anal veins in Hw, with at most 2 cells doubled.... 3

2 (1) Clypeus all brown. Thorax without distinct yellow markings. S3–6 entirely reddish brown except for the black posterior field of tergites forming contrasting rings. Anterior branch of the hamule broad and bent down subapically, with beak-like tip. Cerci in dorsal view rather straight at base and diverging gradually in distal half. Rspl subtending doubled cell row for 3–7 cells................................................................................ N. rubricauda Martin, 1900

– Clypeus yellow at centre. Thoracic mesepimeron and metepimeron each with yellow spot contrasting with surrounding darker colouration. S3–6 each with a triangular black posterolateral smudge bordering the posterior black rings. Anterior branch of the hamule tapered distally into a triangular and unbent tip. Cerci in dorsal view with arched base and out-curved tips, thus appearing sinusoidal or lyre-shaped. Rspl subtending single row of cells............................. N. fossa sp. nov.

3 (1) Each of S7–10 largely yellow dorsally, only marked distally with black. Ventrolateral side of fore femora dark with contrasting yellow spot at about mid-length. Postclypeus entirely dark and glossy. Postgenae brown with contrasting yellow markings. Cerci ventrally at about third of their length from base with distinct downward spine. Anterior laterodorsal spots on S2 evenly narrow and arched............................................................ N. flavicauda McLachlan, 1882

– Each of S7–10 largely black or reddish brown dorsally, at most with yellow markings basally on S7–8. Ventrolateral side of fore femora with some yellow extending from their base. Postclypeus with broad yellow centre. Postgenae wholly black. Cerci ventrally smooth, without downward spine. Anterior laterodorsal spots on S2 broad, typically narrowing distally into a curved point................................................................................................ 4

4 (3) Poststernum dark brown, like the thoracic background. Epiproct dark brown to black. Lower yellow spot on metepimeron small, much less than half as long as posterior border of metepimeron and not reaching poststernum. Lateroventral yellow marking on S2 divided into two small well-separated spots. Lateral lobes of labium two-coloured, yellow with contrasting blackish markings. Wing membrane tinted with yellow at base.................................................. 5

– Poststernum predominantly yellow, like the thoracic spots. Epiproct largely white, yellow or pale brown. Lower yellow spot on metepimeron large, at least half as long as posterior border of metepimeron and reaching poststernum. Lateroventral marking on S2 single and large, at most narrowed. Lateral lobes of labium yellow, at most with faint dark smudges; brown in the Comoros. Wing membrane hyaline at base................................................................. 6

5 (4) Both branches of hamule broad and rounded, ear-like. Labium with lateral lobes largely blackish brown, only narrowly yellow on outer borders, like crescents. Basal two-thirds (up to 80%) of cerci dark, their pale tips covered with contrasting dark hair-like setae. Total length about 47 mm, Hw 33–34 mm .............................................. N. ipsio sp. nov.

– Both branches of hamule distinctly narrowed and pointed, like fingers. Labium with lateral lobes largely yellow, only narrowly dark along their inner borders. Basal third (up to 40%) of cerci dark only, remainder yellowish white covered mostly with similarly pale hair-like setae. Total length about 54 mm, Hw 37 mm ............................. N. odonator sp. nov.

6 (4) Cerci broadest apically, with clearly swollen tips, appearing clubbed. Labium brown, distinctly darker centrally. Only known from Mohéli, Comoros............................................................ N. villiersi Legrand, 1984

– Cerci not distended apically, even if broadest subapically, always gradually tapering towards apices. Labium pale (yellow, ochre yellow), at most with faint darker smudges. Only on Madagascar................................................ 7

7 (6) S8 black with pair of narrow dorsolateral yellow spots at base. Cerci angled at 40% of their length from base with a broad downward tooth (visible in lateral view) and with down- and in-curved tips, like an earwig’s forceps in dorsal view. Epiproct reaches about halfway cerci. Genital lobe pointed...................................... N. spinicauda Martin, 1902

– S8 entirely black or reddish brown. Cerci without a strong ventral tooth and gradually curving outwards distally. Epiproct reaches at least two-thirds of the cerci length. Genital lobe rounded.............................................. 8

8 (7) Cerci in dorsal view sinusoidal, with arched base and out-curved tips, recalling a Roman lyre. Basal yellow spot on S7 extends dorsally beyond the supplementary transverse carina and also extends laterally, merging with the yellowish markings on the ventral carina. Mesepimeron and metepisternum marked with a single narrow and kinked yellow stripe. Total length 58–60 mm, Hw 40–41 mm, Fw Ax 13–15, Fw Px 11–13, Hw Px 13–14.................................... N. lyricauda sp. nov.

– Cerci in dorsal view diverging gradually, rather straight at base. Basal spot on S7 more limited, not extending beyond the supplementary transverse carina and not reaching the yellowish markings on the ventral carina, or spot is absent. Mesepimeron and metepisternum with two distinct spots, which may be fused into one broad irregular marking. Total length 43–53 mm, Hw 28–35 mm, Fw Ax 10–13, Fw Px 7–10, Hw Px 7–11......................................................... 9

9 (8) S7–10 mostly reddish brown, contrasting with black remainder of abdomen...................................... 10

– S7–10 mostly black, like rest of abdomen................................................................. 11

10 (9) S7 dorsally reddish brown with large basal yellow spot (may be absent locally). Mesepimeron and metepisternum marked with single large, broad and irregular yellow spot, sometimes narrowly divided into two spots. Metepimeron with single long yellow marking. Occipital triangle yellow. Frons laterally pure yellow. Labrum with extensively yellow centre. In dorsal view, cerci fairly thick, basally converging and then diverging, with inner margin slightly angled near base..... N. coloratissima sp. nov.

– S7 uniformly reddish brown. Mesepimeron and metepisternum with two broadly separated spots. Metepimeron with two distinct yellow spots. Occipital triangle black. Frons laterally dark metallic (at most partly yellowish brown). Labrum with two small yellow spots at base. In dorsal view, cerci more slender, basally straight and while diverging for distal half subtly converging at extreme tips, with smooth inner margin.................................... N. malgassica Fraser, 1956

11 (9) Dorsal process (keel) on S10 long and rather erect. Supertriangles free of cross-veins. Metepimeron with two small and widely separated yellow spots. Yellow spot at base of S7 continuous across dorsal carina. In lateral view, posterior branch of hamule broader but not much longer than anterior branch. At least tip of genital lobe black. In dorsal view, cerci slightly arched inwards and relatively thick with slightly distended distal half.......................................... N. evanida sp. nov.

– Dorsal process (keel) on S10 short and almost horizontal, directed posteriorly. Supertriangles crossed in all wings. Metepimeron with one large (at most slightly incised) yellow spot. Yellow spot at base of S7 interrupted by black on dorsal carina. In lateral view, posterior branch of hamule much longer than anterior branch. Genital lobe completely yellow. In dorsal view, cerci almost straight, thin, and not distended................................................... N. mascarenica Fraser, 1948