Nesocordulia spinicauda Martin, 1902

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 : 177-179

Nesocordulia spinicauda Martin, 1902 —Pincer-tipped Knifetail

Figs 12 , 15 , 17–19

Etymology. A feminine noun derived from Latin “cauda”, a tail, and “spina”, a thorn or spine, probably describing the spinelike dorsal process on S10. Dijkstra & Cohen (2021) followed the scientific name in calling the species “Spine-tailed Knifetail”. As the spinelike keel on S10 is found in all Nesocordulia males, a new common name recognising the uniquely shaped appendages is proposed above.

Type material. Two males and three females ( MNHN), lectotype male and four paralectotypes designated by Legrand (1984); Fort-Dauphin (present Tôlanaro), Anosy Region, Madagascar, leg. Charles Alluaud, January of 1901, the year not given in the original description, but deduced from details known of the expedition ( Jeannel 1952).

Diagnosis. Medium-sized Nesocordulia species, unique among the black-tailed species by its comparatively long (relative to both abdomen and epiproct) and forcipate cerci, sharply pointed genital lobe, and narrow dorsal yellow markings on S8. By contrast, the undivided hamule has rather a simple form. The markings on the synthorax are similar only to those of N. lyricauda , which however also differs by its greater size, distinctive divided hamule ( Fig. 15 ), and both shape and size of basal yellow spots on S7.

Description. All specimens, 124 years ‘old’, preserved at most in a moderate state, with damaged or partly damaged male appendages and partly faded or darkened yellow pattern.

Lectotype male. Total length 52.2, abdomen (excluding appendages) 36.2, Fw 36.5, Hw 35.3, Fw Pt 2.1, cerci 3.5. Fw Ax 11–12, Fw Px 8, Hw Ax 7–8, Hw Px 9. Colouration generally dark, black and metallic, with yellow pattern ( Fig. 12 ).

Head. Face dark, largely metallic, with a yellow slightly trapezoidal centre ( Fig. 12c ). Vertex metallic blue and violet. Frons with brown background (visible in frontal shield), largely with metallic reflections (green, blue, violet, copper and bronze) ( Fig. 12c ). Postclypeus broadly yellow centrally with metallic green sides. Anteclypeus yellow ( Fig. 12c ). Labrum dark, glossy black and bronze ( Fig. 12c ). Labium yellow ( Fig. 12a ). Occipital triangle black. Postgenae black.

Thorax. Synthorax largely with metallic reflections, mostly green and blue and locally dark bronze and copper, and with large yellow spots ( Figs 12a,b ). Mesepisternum with metallic green and blue reflections and yellowish brown anterolateral corner. Mesokatepisternum brown. Three yellow spots on synthoracic sides: (a) a single upper stripe on mesepimeron and metepisternum, long, narrow and kinked; (b) a small spot on the metakatepisternum below the metastigma; and (c) a long and wide rectangular marking covering the posterior half of metepimeron and adjacent to the yellow poststernum ( Figs 12a,b , 19 ).

Wings. Membrane not tinted yellowish, at most a trace at the Hw base. Pt short, brown.

Abdomen. Black with paired yellow pattern. The laterodorsal spots on each side of S2 are of different shape and size: the anterior patch broad, with tapered tip directed dorsally, and the posterior one small, angular, directed obliquely ventrally. The broad yellow lateroventral spot on each side of S2 stretched along the whole segment and penetrating the genital lobe, with a dorsal black ‘bay’ below an auricle ( Fig. 12d ). The laterodorsal paired yellow pattern on S3–6 consists of anterior stripes on each segment and posterior stripes on S3 only. S7 with two basal laterodorsal yellow spots, broadly diverged dorsally and fairly small, covering one fifth of the segment’s length and not reaching far laterally (at most to the segment’s half-height) ( Fig. 12e ). S8 with two very narrow transverse yellow spots at the base ( Fig. 12e ). The pale pattern along the ventral carina (yellow to brownish yellow, partly faded/darkened): (a) on S3–7, a line, broadened anteriorly on S3 only, on S7 without any adjacent spot; (b) on S8, a large irregularly triangular spot, the broadest in its anterior half ( Fig. 12f ); (c) on S9, an anterior broad spot; spots on S8–9 visible in lateral view ( Fig. 12a ).

Secondary genitalia. In lateral view, the hamule not divided into branches, rectangular, with wavy anterior margin and rounded tips ( Figs 12d , 15 ). Genital lobe exceeding the hamule tip and strongly narrowed terminally, spine-like, with a bent posterior margin thus pointing obliquely posteriorly ( Figs 12d , 15 ); largely dark (brown to black) with a yellow posterobasal area and yellowish ochre hair-like setae.

Caudal appendages. Cerci long and fairly narrow, creamy yellow, basally brown, with brownish shade up to a quarter of the length ( Fig. 12a ). In dorsal view, arched outwards in their distal half with tips pointing inwards, thus resembling carpenter pincers ( Fig. 18 ), but their arch is more gentle in comparison with the original tool, and also with the cerci illustrated in Fraser (1956). In lateral view, straight, with a strong, wide ventral tooth at 40% of their length and with a tip bent and pointing ventrally ( Figs 12a , 17 ). Epiproct creamy yellow, basally brownish, and short, reaching half of the cerci length ( Figs 12a , 17 ).

Variation in males. The paralectotype is smaller, total length 49.5, abdomen (excluding appendages) 35.1, Fw 34.9, Hw 33.4, Fw Pt 2.0, cerci 3.3. Fw Ax 11, Fw Px 7–8, Hw Ax 8, Hw Px 7–8. The colour pattern almost the same, only the posterior laterodorsal spot on S2 larger, of similar size as the anterior one.

Paralectotypes females. Total length 47.6–49.9, abdomen (excluding appendages) 34.4–36.9, Fw 36.4–37.0, Hw 33.2–35.1, Fw Pt 2.4–2.5, cerci 2.1–2.2. Fw Ax 11–13, Fw Px 7–8, Hw Ax 7–8, Hw Px 8–10. The female colour pattern very similar to that of the males ( Fig. 12h ) with the following minor differences: (a) abdominal paired yellow pattern on S3–6 complete, although posterior stripes on S5–6 very short in two females ( Fig. 12g ), and in one female a small posterior spot even on S7; (b) basal laterodorsal spots on S7 longer than wide, slightly trapezoidal ( Fig. 12g ); (c) broad wing bases tinted with bright yellow to Ax3, including supertriangles in Fw and triangles in Hw ( Fig. 12i ). Cerci relatively long (2.1–2.2), creamy yellowish (possibly whiter in live) ( Fig. 12g ).

Distribution. Known only from Tôlanaro in southeastern Madagascar ( Fig. 21 ) in the ecoregion of Madagascar Humid Forests ( One Earth 2024) and the hydrographic ecoregion of Eastern Lowlands ( Sparks & Stiassny 2022).

Figures

FIGURE 12. Nesocordulia spinicauda. (a) male habitus in lateral view; (b) male synthorax in lateral view; (c) male head in frontal view; (d) male hamule and genital lobe in lateral view; (e) male S7–9 in dorsal view; (f) male S7–9 in ventral view; (g) female habitus in dorsolateral view; (h) female head and synthorax in lateral view; (i) female left wings. 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”).