Nesocordulia mascarenica Fraser, 1948

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 : 173-175

Nesocordulia mascarenica Fraser, 1948 —White-tipped Knifetail

Figs 10 , 15 , 17–19

Etymology. A feminine adjective, of unknown origin, but probably after the Mascarene Islands. Fraser (1948) did not explain why he named a dragonfly from Madagascar after these islands ( Mauritius, Réunion, Rodrigues) or their namesake, the Portuguese navigator Pedro de Mascarenhas. Unaware of the many dark species with pale appendages, Dijkstra & Cohen (2021) called this the “White-tipped Knifetail”.

Type material. Holotype male ( NHMUK 012502442 ), Mandritsara (without further data), Sofia Region , Madagascar, leg. W. Janson. Fraser (1948) described an allotype female ( MNHN), just labelled “ Madagascar ”, from René Martin’s collection, which must thus have been collected before 1921. This does not appear to be conspecific with the holotype (see section on unidentified specimens below).

Diagnosis. Rather small Nesocordulia species easily separated by the uniquely slender and almost straight cerci, as well as the hamule with its long posterior branch. The thoracic pattern of yellow spots, crossed supertriangles and wholly yellow genital lobe appear to be distinctive too. The short and down-turned, almost horizontal dorsal process (keel) on S10 is unlike in any other species except the otherwise very distinctive N. flavicauda .

Description. Holotype male. Total length 46.1, abdomen (excluding appendages) 31.4, Fw 32.2, Hw 32.3, Fw Pt 1.7, cerci 2.3. Fw Ax 12–13, Fw Px 8–9, Hw Ax 7, Hw Px 8–10. Colouration generally dark, black and metallic, with yellow pattern ( Figs 10a,b ).

Head. Face dark, metallic with a yellow centre ( Fig. 10d ). Vertex, frons and sides of postclypeus with metallic reflections: largely green, but also locally blue on vertex and postfrons, and copper on sides of frons and postclypeus ( Figs 10b,d ). Anteclypeus and central postclypeus yellow. Labrum glossy black ( Fig. 10d ). Labium ochre yellow. Occipital triangle black. Postgenae black.

Thorax. Synthorax largely metallic green and glossy black (with blue and copper reflections locally), with yellow spots ( Fig. 10b ). Middorsal carina brown. Mesepisternum metallic green with a brownish yellow spot in the anterolateral corner ( Figs 10a,b ). Yellowish spot on the mesokatepisternum. Synthoracic sides with four yellow spots in two lines ( Figs 10b , 19 ). In the upper line, two quite large, elongated spots, the mesepimeral triangular spot with a slightly curved and blunt tip obliquely pointing dorsally, and the metepisternal spot, ribbon-like and bluntly pointing ventrally. In the lower line, two markings along the lower margin of synthorax, a small spot on the metakatepisternum below the metastigma and a long and broad (at most slightly incised) spot, stretched along the most of metepimeron and adjacent to the yellow poststernum.

Wings. Membrane hyaline. Pt very short, dark brown ( Fig. 10a ). Supertriangles crossed in all wings ( Fig. 10a ).

Abdomen. Black, with paired yellow pattern ( Fig. 10a ). The laterodorsal spots on each side of S2 are of similar size: the anterior spot broad, with tapered tip directed dorsally, and the posterior one oval ( Fig. 10a ). The lateroventral yellow spot on each side of S2 stretched along most of the segment’s length; narrower anteriorly and broader posteriorly, distally covering the whole genital lobe ( Fig. 10b ). The laterodorsal yellow pattern on S3–6 consists of anterior stripes on all segments and posterior stripes on S3 only ( Fig. 10a ). S7 with a basal dorsolateral half-ring, covering one fifth of the segment’s length and broadly divided along the black dorsal carina ( Figs 10a,e ). Along the ventral carina of S3–6, a pale yellow line broadened anteriorly on S3 only ( Fig. 10c ). On S7, the yellow ventral carina broadened brownish; on S8, ventral carina yellowish to brownish, with a large yellowish spot above; both broadenings on S7 and S8 visible in lateral view ( Figs 10c,e ). Dorsal process (keel) on S10 weakly defined, short (shortly pointed) and down-turned, almost horizontal ( Fig. 10e ).

Secondary genitalia. In lateral view, the hamule large, with a significantly longer posterior branch forming a quite long tip like a blunt claw curved towards the front ( Figs 10b , 15 ). An adjacent anterior branch much smaller, nestled at the base of the posterior ‘claw’. Genital lobe relatively short, directed obliquely posteriorly, and totally yellow, with ochre yellow hair-like setae ( Figs 10b , 15 ).

Caudal appendages. Cerci fairly short and thin, creamy yellowish, with dark brown base (brownish shade up to one third of the length) and pale hair-like setae ( Fig. 10e ). In dorsal view, almost straight, slightly divergent in their distal half and not distended ( Fig. 18 ). In lateral view, slightly arched up, with a blunt kink at two thirds of the lower edge, and with straight and gently tapering tips ( Figs 10e , 17 ). Epiproct light brown, darkening towards the black tip, and fairly long, reaching three quarters of the cerci length ( Figs 10e , 17 ).

Distribution. Known only from the type locality in northeastern Madagascar ( Fig. 21 ). Since this site cannot be located precisely, it cannot be assigned to an ecoregion (possibly Madagascar Subhumid Forests, sensu One Earth 2024) or hydrographic ecoregion as both Northwestern Basins and Eastern Highlands ( Sparks & Stiassny 2022) are possible.

Figures

FIGURE 10. Nesocordulia mascarenica, male. (a) habitus in dorsal view; (b) head, synthorax and S1–3 in lateral view; (c) abdomen in ventral view (its colour falsely reddish, in fact, it is yellow); (d) head in frontal view; (e) S7–10 and caudal appendages in lateral view. Photos by Bogusław Daraż.

FIGURE 15. Lateral view of hamule and genital lobe of all species of Nesocordulia except N. flavicauda. Arranged according to similar form to aid comparison. Due to the poor quality of the available material, the actual shape of the N. malgassica hamule may differ in detail.

FIGURE 17. Lateral view of caudal appendages of all known species of Nesocordulia. Showed to scale. Hair-like setae not illustrated. Arranged according to similar form and size to aid comparison.

FIGURE 18. Dorsal view of caudal appendages of all known species of Nesocordulia. Showed to scale. Hair-like setae not illustrated. Arranged according to similar form and size to aid comparison.

FIGURE 19. Lateral view of synthorax of all known species of Nesocordulia. Arranged by extent and form of clear yellow spots (but not the indistinct brownish-yellow ones indicated by a slightly darker shade) to aid comparison. All darker colouration (i.e. more or less melanised, from reddish brown to black) is indicated by the dark shading.

FIGURE 21. Distribution of known localities of Nesocordulia. For further details see the species texts. “flavicauda?”— unconfirmed records in the Sambirano area; “Nesocordulia sp.”—several unidentified specimens from collections and photographs (see Fig. 14 and section “Unidentified specimens of Nesocordulia”).