Nesocordulia flavicauda 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 : 168-171

Nesocordulia flavicauda McLachlan, 1882 —Yellow-tailed Knifetail

Figs 8 , 15 , 17–19

Etymology. A feminine noun derived from Latin “flavus”, yellow, and “cauda”, a tail, undoubtedly, to emphasise the extent of yellow on S7–10. Unaware of its unique appearance, Dijkstra & Cohen (2021) called this species the “Yellow-tailed Knifetail”, a translation of the scientific name.

Type material. Holotype male (NHMUK 011253668), just labelled “ Madagascar ”, but obviously collected no later than 1882.

Additional material. Female ( MNHN), also just labelled “ Madagascar ”, but from René Martin’s collection and thus collected before 1921; described by Fraser (1956). Note: In the catalogue of corduliids ( Martin 1907), N. flavicauda is presented erroneously, as Martin must not have seen McLachlan’s holotype and thus misidentified a male in his own collection. The male described and illustrated (caudal appendages) by Martin (1907) is described above as the holotype of N. lyricauda sp. nov. The female described briefly by Martin (1907) as N. flavicauda is probably not this species either. Fraser (1956) found two females in Martin’s collection labelled as N. flavicauda : only one of them was originally identified correctly, but the second was identified and described by him as N. mascarenica . We seriously doubt this identification as well, however, see the section on unidentified specimens below. The brief description of a female by Martin (1907) does not allow us to determine precisely which female he described as N. flavicauda , although the provided measurements suggest Fraser’s ‘ mascarenica ’ rather than true N. flavicauda . Therefore, only Fraser’s (1956) work can be accepted as the first description of the female N. flavicauda .

Uncertain data. 2 males and 1 female ( National Museum of Nature and Science, Tokyo, Japan, most probably from the Erich Schmidt’s collection) : 1 male and 1 female, Sambirano (without closer data), Diana Region, NW Madagascar, 10.1933 –01.1934 ; 1 male, Madagascar (perhaps the same locality?), 02.1934 ( Kiyoshi 2024). Note : This material was unavailable for study and may well be misidentified .

Diagnosis. Fairly small Nesocordulia species, which is the most distinctive in the genus due to the spined cerci and numerous colouration details such as the entirely dark postclypeus, brown and yellow postgenae, two yellow spots on synthoracic sides, yellow central spot on ventrolateral surface of fore femora, evenly narrow and arched anterior dorsal yellow spot on S2, and very large yellow spots on S7–9. Dorsal process (keel) on S10 is shortly pointed and almost horizontal unlike in most other Nesocordulia species (except N. mascarenica ), in which it is more knife-shaped and vertically or at least obliquely protruding.

Description. Holotype male. Preserved in poor condition, in several damaged fragments ( Figs 8a,d ), but most features still sufficiently recognisable. Additionally, the original description from 143 years ago ( McLachlan 1882) has been confronted to make sure of the original colours and other features. Total and abdomen lengths unmeasurable in the present state, McLachlan (1882) gave 35 mm for the abdomen length (caudal appendages included?). Fw length 33.7, Hw 32.7 (34 according to McLachlan, 1882), Fw Pt 1.8, cerci 2.8 (3¾ according to McLachlan, on error). Fw Ax 10, Fw Px 8–9, Hw Ax 7, Hw Px 9–10. Colouration generally dark, black, brown and metallic green, with yellow pattern ( Figs 8a–d ).

Head. Face dark, largely brown and locally metallic, only with a narrow yellow stripe ( Figs 8f–g ). Vertex metallic green with golden reflections in posterior parts. Postfrons metallic with green and blue reflections ( Figs 8a,f ). Frontal shields of antefrons rich brown ( Fig. 8f ). Antefrons sides yellowish brown to metallic with green, copper and golden reflections ( Fig. 8b ). Postclypeus entirely dark, glossy black centrally and metallic green and bronze laterally.Anteclypeus yellow ( Figs 8f,g ). Labrum brown with patina green tint ( Figs 8f,g ). Labium variegated, with median lobe brown and lateral lobes two coloured: ochre yellow laterally and brown with green patina centrally ( Fig. 8g ). Occipital triangle brownish to black. Postgenae brown with yellow markings ( Fig. 8b ).

Thorax. Synthorax dark brown (tinted green patina locally) with metallic reflections locally and yellow spots ( Fig. 8b ). Middorsal carina brown. Mesepisternum largely metallic green. Synthoracic sides with three pale spots ( Figs 8b , 19 ): a small dull ochre yellow spot on the metakatepisternum below the metastigma and two large yellow spots: an upper oblong, comma-like spot on the mesepimeron, and a lower more oval spot along the posterior margin of metepimeron. Both bright spots encircled with metallic areas, with mostly green, but also blue, violet and reddish copper reflections, the last concentrated in a distinct patch below the mesepimeral yellow spot. No yellow spot on metepisternum. Poststernum brown ( Fig. 8b ). Legs generally black with (partly) brown coxae and trochanters. Fore femora, on ventrolateral surface, with yellow central spot flanked with brown basally and black distally ( Fig. 8b ).

Wings. Membrane tinted with yellow in a very small but bright basal spot in all wings ( Fig. 8a ). Pt short, rich brown ( Fig. 8a ).

Abdomen. Background dark brown and black, with increasing proportion of the latter from S2 posteriorly, patterned with paired yellow spots ( Figs 8a–d ). On S2, only anterior laterodorsal spots present, evenly narrow and arched ( Figs 8a,c ). In place of posterior laterodorsal spots, two paler brown transverse stripes. Lacking lateroventral spot on S2, only a small yellowish brown marking at the base of the genital lobe. Similarly, on S3–6, only anterior laterodorsal stripes, all gently curved with distal tips directed towards the twin stripe; in place of posterior stripes on S3–4, only paler brown irregular shade ( Figs 8a,c ). S7 with a large dorsal yellow spot covering the anterior half of the segment, with two distal projections reaching 70% of the segment’s length ( Fig. 8d ). S8 dorsally with two large triangular yellow spots, basally fused in a half-ring covering 40% of the segment’s length and distally diverging and dissipating in yellow-brown melange, with tips reaching 80% of the segment’s length ( Fig. 8d ). S9 dorsally mostly covered by two large spots, basally yellow and distally brownish, diverged by a blackish stripe along the dorsal carina. Dorsal process (keel) on S10 small, shortly triangular and almost horizontal ( Fig. 8e ).

Secondary genitalia. Hamule destroyed. Genital lobe rather narrow, directed downwards, brownish black with pale base.

Caudal appendages. Cerci medium-length and relatively stout, creamy yellow with blackish hair-like setae ( Figs 8d,e ). In dorsal view, almost straight in basal one third of the length and then strongly divergent and tapered into blunt tips ( Figs 8d , 18 ). In lateral view, almost straight, with a sharp triangular spine pointing ventrally at about one third of the length and with tips blunt with an undercut lower edge ( Figs 8e , 17 ). Epiproct chocolate brown, brightened subapically, but with a black apical tooth; short, reaching half of the cerci length, and stout ( Figs 8e , 17 ).

Female. Preserved in poor condition, in several parts ( Figs 8h,i ). Total and abdomen lengths no longer measurable, Fraser (1956) provided 35 mm as the abdomen length. Fw length 37.2, Hw 35.3, Fw Pt 1.9, cerci 1.2. Fw Ax 10–12, Fw Px 9–10, Hw Ax 7, Hw Px 10–12. Appears in pre-reproductive period, with pale yellow Pt, and collapsed eyes and synthorax. Many features are difficult to ascertain, although several agree with those of the male, notably the largely brown background colour of the head and synthorax, and the markings on the postgenae, synthorax, fore femora, wing bases, and S2 ( Fig. 8h ). Central postclypeus not uniform as in the male, but two-toned: brown with an upper yellowish line below the epistomal suture.

Distribution and ecology. Unknown.

Figures

FIGURE 8. Nesocordulia flavicauda. (a) male habitus (partial) in dorsal view; (b) male head, synthorax and S1–3 in lateral view; (c) male S1–4 in dorsal view; (d) male S7–10 and caudal appendages in dorsal view (falsely reddish tint, in fact, more yellow); (e) male S8–10 and caudal appendages in lateral view; (f) male head in frontal view (g) male head in anteroventral view; (h) female head and synthorax in lateral view; (i) female abdomen 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.