Nesocordulia evanida Bernard, Daraż & Dijkstra, 2025

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 : 156-159

Nesocordulia evanida Bernard, Daraż & Dijkstra sp. nov. —Little Knifetail

Figs 2 , 15– 19 , 20e

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Etymology. A declinable feminine Latin adjective meaning “vanishing from sight”, as males are almost impossible to follow for the observer’s eyes due to the combination of their behaviour, disruptive camouflage, and the dappled light in their microhabitat (see Behaviour section).

Type material. Holotype male (NHC-T-INS-000011), and six paratypes, five males (NHC-T-INS-000012, NHC-T-INS-000013, NHC-T-INS-000014, NHC-T-INS-000015, NHC-T-INS-000016) and a teneral female ( NHC- T-INS-000017), collected after emergence before maiden flight, all from the Simianona river , a bridge 1.9 km SSE of Antsiatsiaka, 16.3116° S, 48.8541° E, 853 m asl, Sofia Region, Madagascar, 7 and 12.12.2023, leg. R. Bernard, B. Daraż and Mamitiana Rakotohary.

Additional material. 1 male, incomplete, S7–10 missing ( RMNH.INS.1552539), the Manantenina river and adjacent rice fields, between Mandena village and the Marojejy National Park border, 14.4690° S, 49.8058° E, 107 m asl, Sava Region, 15.02.2018, leg. K.-D.B. Dijkstra.

Diagnosis. The smallest Nesocordulia species, separated from its probable closest relatives ( N. coloratissima and N. malgassica ) by the black rather than rufous S7–10 and its slightly, but distinctively distended cerci with black hair-like setae. Differs from other black-tailed species by the shape of the cerci and hamule, as well as the thoracic markings with two triangular and three roundish yellow spots on each side.

Description. Holotype male. Total length 44.3, abdomen (excluding appendages) 30.8, Fw 29.5, Hw 28.5, Fw Pt 1.8; cerci 2.0. Fw Ax 11, Fw Px 7, Hw Ax 6, Hw Px 8–9. Colouration generally dark, black and metallic green with yellow pattern ( Fig. 2a ).

Head. Face dark metallic with a yellow centre ( Fig. 2g ). Vertex and frons metallic, with green and blue reflections ( Figs 2c,g ). Frons sides brownish turning into metallic green with golden and copper reflections. Clypeus largely yellow, with metallic green sides. Labrum black, with two small yellow spots at the base ( Fig. 2g ). Labium yellow, median lobe paler with a small central darkish spot. Occipital triangle black. Postgenae black. Eyes in life purplish brown anterodorsally, and blue posteroventrally, with a bright green line in between ( Fig. 2a ).

Thorax. Synthorax mostly metallic (largely green and locally blue and copper), with darker lower parts (purplish-dark brown to blackish), and with five yellow spots on sides ( Figs 2a , 19 ). Two upper spots fairly large, elongated, irregularly triangular, with opposite tips: the mesepimeral pointing dorsally, and the uppermost metepisternal pointing ventrally. Along the lower margin, three small spots, the first on the metakatepisternum below the metastigma and two next on metepimeron, the last spot adjacent to mostly yellow poststernum (with brownish tip). Middorsal carina yellow, contrasting with the metallic green reflections on mesepisternum ( Fig. 2c ).

Wings. Membrane basally hyaline, without any tint. Pt medium-sized, black.

Abdomen. Black, with paired yellow pattern ( Fig. 2f ). The laterodorsal yellow spots on each side of S2 are of similar size: the anterior spot broad, with tapered tip directed dorsally, and the posterior one oval ( Figs 2a,f ). The lateroventral yellow spot stretched along most of the S2 length; narrow anteriorly, broad posteriorly, with a short dorsal branch pointing an auricle ( Figs 2a,d ). The laterodorsal yellow pattern on S3–6 incomplete, it consists of anterior stripes on S3–5, and posterior stripes on S3 and S4 (vestigial) ( Fig. 2a ). S7 with a basal dorsolateral yellow half-ring covering one quarter of the segment’s length and reaching the supplementary transverse carina; dorsally, the ring is complete, with a small apical notch flanked by two tiny distal projections ( Figs 2a,f ). Along the ventral carina: (a) on S3–6, a pale yellow line, broadened anteriorly on S3 only; (b) on S7, a small brownish yellow spot basally and a yellow to brownish stripe; (c) on S8, a large brownish spot (thinner distally), visible in lateral view ( Fig. 2e ).

Secondary genitalia. Hamule in lateral view, with a fairly shallow and rather narrow triangular apical incision between anterior and posterior branches, the former short and tapered and the latter slightly longer, broader and rounded apically ( Fig. 15 ). In ventral view, the inner lobe of the anterior branch broad and slightly tapered inwards; at the apex, the anterior branch shallowly divided from the posterior external branch, which is slightly twisted inwards and visible as pale roundish surface with a broad black margin ( Fig. 16b ). Genital lobe relatively narrow, directed obliquely posteriorly, with yellow hair-like setae.

Caudal appendages. Cerci fairly short, creamy white, black basally (brownish shade to 40% of the length), with black hair-like setae ( Figs 2a,h ). In dorsal view, gently arched inwards, with a longer (60%) and slightly distended outward arm ( Fig. 18 ). In lateral view, slightly bent down at one third of their length, further distally slightly distended thus looking hanging down ( Figs 2h , 17 ); the small bulge hardly discernible at one quarter of the length. Epiproct creamy white with a darkish base and blackish apex; fairly long, reaching 70% of the cerci length ( Figs 2h , 17 ).

Variation in males. Total length 43.2–44.6, abdomen (excluding appendages) 29.1–31.0, Fw 29.5–30.8, Hw 28.5–29.9, Fw Pt 1.8–2.0, cerci 2.0–2.2, Fw Ax 10–11, Fw Px 7–8, Hw Ax 6–7, Hw Px 7–9. Differences in colouration limited only to: (a) larger or smaller width of two upper synthoracic spots; (b) laterodorsal yellow pattern on S3–6 more or less developed in individuals from the same local population: the anterior stripes more frequently on S3–6 ( Fig. 2f ), but also on S3–5 (with that on S5 even vestigial, Fig. 2a ), and posterior stripes usually on S3 only, but also on S3–4; (c) the lateroventral spot on S2 without a dorsal branch in one male; (d) the background colour of S7–10 brownish black in one male; (e) various size of two small distal projections of the yellow half-ring on S7, from lacking to quite well developed with disintegrating brownish tips; (f) the brownish shade on cerci reaching their half-length and even three quarters of their length (each version in one specimen).

Paratype female. Teneral, preserved in poor condition. Total length 41.6, abdomen (excluding appendages) 29.6, Fw 31.7, Hw 30.9, Fw Pt 2.0. Fw Ax 13, Fw Px 8, Hw Ax 7, Hw Px 9–10. Although the colouration in this female is not fully developed, it is generally similar to that of the males with the following minor differences ( Fig. 2b ): (a) two upper thoracic spots, mesepimeral and metepisternal, wider (as in the male from Marojejy); (b) two metepimeral yellow spots partly merged into large one; (c) the laterodorsal pattern on S3–6 more complete, with anterior stripes on all segments (S3–6), and posterior stripes on S3–5 (on S5 vestigial); (d) pattern along the ventral carina: on whole S7, a broad yellow stripe broadened anteriorly, and on S8, a yellow spot, large and rounded in its anterior half, and narrowed in its posterior half. Gonapophyses ( Fig. 20e ): (a) anterior processes at the end of S8 (subgenital plate) in the form of two short and broad, rounded projections, laterally situated and partly covered by tergites; and (b) median processes on S9 as vertical, narrow, rather long and tapered warts. Cerci tiny (0.7), white with darkish shade dorsally along the basal half.

Distribution and ecology. Known from two localities situated 229 km apart in northeastern Madagascar ( Fig. 21 ), the type locality being in the ecoregion of Madagascar Subhumid Forests and the second site in the ecoregion of Madagascar Humid Forests ( One Earth 2024). Both sites are in the hydrographic ecoregion of Eastern Highlands ( Sparks & Stiassny 2022) at the foot of mountainous protected areas, the type locality lying just below Marotandrano Special Reserve and the second site below Marojejy National Park. The Simianona river originates in extensive foothill marshland and flows through a mosaic of forest, thickets and wetlands with a relatively low degree of human impact. The Manantenina river flows down from the Marojejy range, but the collection locality is in a cultivated landscape two kilometres from closed forest. The Simianona river ( Fig. 3 ) is mostly 7–10 (up to 15) m broad and relatively deep with water clear, but appearing dark brown due to its marshy origin. The flow rate is very low, slightly increasing only where the course narrows and at some small cascades. The banks are mostly overgrown by low trees with their branches and even trunks overhanging the water. Consequently, the river surface is a mosaic of complete shade, half-shade, dispersed light, and sunny clearings, while the shore zone is mostly shaded ( Fig. 3 ). At a few open sections, dense floating mats of ferns and sedges ( Cyperaceae ) extend over the water surface, with patches of Nymphaea caerulea waterlilies along them. The calm river changes its character on short sections with multi-stage cascades and rapids, where habitat conditions become more diverse.

Behaviour. Males were observed (and filmed) at the Simianona river almost only during sunny moments (with one exception), typically remaining for no more than 3–5 minutes. They only flew over shaded and half-shaded sections, never entering larger sunny clearings. Together with their colouration and rapid, erratic flight, this provided disruptive camouflage and made following them for more than a few seconds almost impossible. The areas patrolled covered only 3–10 m 2, the smallest being in deep shade above foaming water below a cascade, while the largest was occupied during the only observation in overcast weather. Territories were mostly close to the shore (0.2–1.5 m) or along overhanging trees further out; only occasionally males flew even further above open water. The males’ flight was highly erratic with rapid sharp turns after every 0.5–1.5 m section covered. Any moments of hovering were brief with the male facing the open river with its abdomen slightly raised. Males mostly flew only 20–30 cm above the water, ranging between 10 and 40 cm. Males of Hemicordulia similis ( Rambur, 1842) patrolled nearby but favoured more brightly lit sections, including completely sunny ones, and their flight was more predictable, going back and forth at a height of 30–50 cm without sudden turns; they hovered less often but did so for longer periods. A mid-air clash between males of N. evanida and H. similis ended with the latter being chased from the territory of the former.

Figures

FIGURE 2. Nesocordulia evanida sp. nov. (a) male habitus in lateral view; (b) female habitus in lateral view; (c) male head and thorax in dorsal view; (d) male secondary genitalia in lateral view; (e) male habitus in ventral view; (f) male abdomen in dorsal view; (g) male head in frontal view; (h) male terminalia in lateral view. Photos by Bogusław Daraż.

FIGURE 3. Habitat at type locality of Nesocordulia evanida sp. nov., Simianona river, Antsiatsiaka. Photo 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 16. Secondary genitalia in ventral view of the six new species of Nesocordulia: (a) N. coloratissima, (b) N. evanida, (c) N. lyricauda (only right side recognisable, the left one damaged), (d) N. odonator, (e) N. ipsio, and (f) N. fossa. Arranged vertically (head upwards) to aid comparison. Photos by Bogusław Daraż.

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 20. S8–9 of female Nesocordulia in ventral view, with gonapophyses: anterior processes (subgenital plate) on S8 and median processes on S9. a–b, N. ipsio; c–d, N. coloratissima, on figure d the anterior processes (subgenital plate) covered by tergites and only their common base discernible; e, N. evanida (the teneral female preserved in poor condition), the anterior processes (subgenital plate) partly covered by tergites (dotted line). Photos by Bogusław Daraż.

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”).