Hemicordulia atrovirens, Dijkstra, Klaas-Douwe B., 2007

Dijkstra, Klaas-Douwe B., 2007, Gone with the wind: westward dispersal across the Indian Ocean and island speciation in Hemicordulia dragonflies (Odonata: Corduliidae), Zootaxa 1438, pp. 27-48 : 34-36

Hemicordulia atrovirens n. sp.

Figs 4, 9 , 14 .

Hemicordulia asiatica nec ( Selys, 1878) – Couteyen & Papazian (2000: 107).

Hemicordulia atrovirens n. sp. Holotype ♂ and paratype Ψ: Réunion, Rivière de Sainte-Suzanne, 730 m a.s.l., 8– 9.iv.1996, A. Martens (RMNH) [examined].

Further material: RÉUNION: 1 Ψ (Coll. Martin), “ Réunion ” ( MNHN); 2 ď, Bras Cabot, 1325 m a.s.l., 4.iv.1996, A. Martens (Coll. A. Martens); 2 ď, Rivière des Marsouins, 1330 m a.s.l., 4.iv.1996, A. Martens (Coll. A. Martens); 3 ď, ravine near Rivière Langevin, 350 m a.s.l., 14.iv.1996, A. Martens (Coll. A. Martens); 1 ď, Chemin-de-Ceinture, forêt de ravenales, 12.ii.1999, J. & Cl. Pierre ( MNHN); 1 Ψ, commune de Saint- Philippe, Ravine Basse Vallée, altitude 280 m a.s.l., 22.v.1999, S. Couteyen (Coll. M. Papazian); 1 ď, Saint- Paul, old watermill, 2 m a.s.l., 1.v.2000, A. Martens (Coll. A. Martens); 2 ď, Saint-Benoit, Bras Cabot, 1100 m a.s.l., xii.2001, S. Couteyen (Coll. M. Papazian); 1 ď, La Plaine des Palmistes, Forêt de Bébour, Rivière des Marsouins, 1330 m a.s.l., 14.ii.2003, D. Grand (Coll. D. Grand).

Diagnosis. Largest and darkest species, with the most extensive and deepest metallic green markings of all species under consideration (see H. virens ).

Description. Holotype male. Measurements (mm): entire length: 51, abdomen length (without appendages): 34, Fw length: 35, Hw length: 34.5, Fw Pt: 2.0. Labium beige, darker anteriorly (discoloured?). Mandibles, genae, labrum, clypeus and narrow area on lower frons brownish yellow; darker on edges. Vertex and dorsum of frons deep metallic green-blue, merging via a deep brown band into yellow area on antefrons (latter is not visible in dorsal view). Antennae, occipital triangle, occiput and postgenae black; paired rounded swellings on occiput lower than in H. africana . Labrum, clypeus, frons, vertex and occipital triangle with long bristly black hairs. Labium, genae and occiput with finer whitish hairs. Prothorax dark brown. Synthorax deep metallic green with weakly contrasting brownish yellow areas on anterior half of mesepisternum and centres of mesepimeron, metepisternum and metepimeron: metallic areas are much wider than the pale areas between them making entire synthorax almost uniformly green. Mesokatepisternum, metakatepisternum and synthoracic venter brownish yellow with metallic green lustre; poststernum posteriorly dark. Synthorax covered with dense pale long hairs, especially long on mesepisternum; shorter, darker and denser hairs on antealar sinus. Legs black save for yellow coxae and a hint at base of fore femora. Keels present on anterior face of apical half of fore tibiae and almost whole length of hind tibiae (just falling short of their bases), but absent on middle tibiae. Venation blackish. Wing membrane evenly but very lightly tinted brown, tinged yellower at extreme bases. Membranule dark brown, slightly paler at extreme base. Pt dark brown. Venation as for genus. 8 Ax in both Fw, 6 in Hw. 7–8 Px in Fw, 9 in Hw. Fw and Hw triangles with single cross-veins. Discoidal field of 2 rows of cells at base. Anal loops of 18 cells. Abdomen black with green- and blue-purple gloss, tergites unmarked except for an indistinct brownish yellow lateral spot on S2, S2–3 intersegmental ring and narrow streaks on lateral carinae S3. Sternites black. Cerci and epiproct slender, black ( Figs 4, 9 ). Cerci with thick, blunt tips. Secondary genitalia similar to H. africana (cf. Fig. 1 ), hamule blackish brown.

Paratype female. Measurements (mm): entire length: 55, abdomen length (without appendages): 39, Fw length: 39, Hw length: 38, Fw Pt: 2.5. Larger and slightly paler than holotype. Paired rounded swellings on occiput more strongly swollen than in male, only with long pale hairs. Pale areas on synthorax larger and brighter, appearing as distinct spots. Fore femora ventrally largely pale. Basal yellow in wings more extensive than in male, to Cux and almost to Ax 1 in Fw, and just beyond Cux and to Ax 1 in Hw. 8–9 Ax in Fw, 6 in Hw. 7 Px in Fw, 9 in Hw. Anal loops of 19–21 cells. Vulvar scale appressed, dark brown, extending over less than a third of sternite S9, semi-circular with deep cleft ( Fig. 14 ). Cerci black, long and slender, 2.5x longer than S10.

Variation. Limited. Pale markings are slightly more extensive in females; teneral specimens were not examined.

Etymology. The Latin atrovirens (being dark green) emphasises both the close relationship and the main difference with its Mauritian neighbour.

Range and ecology. Endemic to Réunion. The larval habitat has been said to range from torrents to stagnant water under closed cover, but is probably principally pools and calm sections of shady fast-flowing streams ( Couteyen & Papazian 2000; Grand 2004; A. Martens in litt.). H. atrovirens seldom cohabits with any of the ten other anisopterans found on Réunion ( Couteyen 2006): overlap (number of sites where two species co-occur as percentage of sites where either or both occur) with each of the nine species shared with mainland Africa was at most 9%, while that with Gynacantha bispina , the only other Mascarene endemic on the island, was 12%. Moreover, within its usual altitudinal range of 300 to 1500 m (one record provided here is near sea level), below 750 m only forested habitats were occupied. Because all nine widespread species avoid forest and six are confined to lower altitudes, Couteyen (2006) suggested that both endemics are out-competed by the mainland species. However, the distribution may also be explained by different habitat preferences (A. Martens in litt.). Males fly along streams, both under forest cover and in full sun. In cloudy weather and towards dusk, adults appear in clearings and on the forest edge, making prolonged flights close to the vegetation ( Couteyen & Papazian 2000; D. Grand in litt.). Adults have been observed from December to May.

Remarks. See H. virens . Paulson & Buden (2003) observed increasing size of H. haluco Asahina with increasing altitude on Pohnpei. The slight size difference seen between H. atrovirens and H. virens , and the darker colour of the latter, may be linked to the greater elevation of the Réunion habitats.

Figures

FIGURE 1. Secondary genitalia of Hemicordulia africana n. sp. in lateral view.

FIGURES 2 – 11. 2 – 6, Male appendages of Hemicordulia species in dorsal view. (2) H. asiatica; (3) H. virens; (4) H. atrovirens n. sp.; (5) H. similis; (6) H. africana n. sp.; 7 – 11, Male appendages of Hemicordulia species in lateral view. (7) H. asiatica; (8) H. virens; (9) H. atrovirens n. sp.; (10) H. similis; (11) H. africana n. sp.

FIGURES 12 – 17. Vulvar scale and S 9 of Hemicordulia species in ventral view. (12) H. asiatica; (13) H. virens; (14) H. atrovirens n. sp.; (15) aberrant H. similis (cf. Fraser 1949); (16) typical H. similis; (17) H. africana n. sp.