Hemicordulia virens (Rambur)

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 : 33

Hemicordulia virens (Rambur)

Figs 3, 8 , 13 .

Cordulia virens Rambur, 1842: 147 . Holotype Ψ: Mauritius (UMO) [not examined]. Cordulia ( Hemicordulia ?) virens ( Rambur, 1842) – Selys (1871: 253 (bulletin), 19 (reprint)). Hemicordulia (?) virens ( Rambur, 1842) – Kirby (1890: 47).

Further material: MAURITIUS: 4 ď, 4 Ψ, Moka, 30.vi.1945 – 30.xii.1948; J. M. Vinson ( BMNH); 1 ď, Macak’Rd, 11.v.1959, leg. unknown ( MNHN); 1 Ψ, F[ôre]t de Machabée, 19.iii.1981, L. Matilé ( MNHN); 1 ď, Cachette, Ruisseau Saint-Denis, 350 m a.s.l., 2.ii.1999, D. Grand (Coll. D. Grand); 1 ď, Cachette, ruisselet forestier, 300 m a.s.l., 2.ii.1999, D. Grand ( MNHN); 1 ď, Rivière Tamarin, 1 m a.s.l., 2.ii.1999, D. Grand ( MNHN); 1 Ψ (head missing), Black River, 120 m a.s.l., 7.iv.1999, A. Martens (Coll. A. Martens); 1 ď, Rivière du Poste, W Grand Bassin, 645 m a.s.l., 12.iv.1999, A. Martens (Coll. A. Martens); 2 ď, Black River, spring area, 680 m a.s.l., 16.iv.1999, A. Martens (Coll. A. Martens).

Diagnosis. Palest and one of the largest species. H. atrovirens from neighbouring Réunion, by contrast, is the darkest known. The two species agree in their large size, high Ax and Px counts, thick blunt-tipped cerci ( Figs 3, 8 ) and the basal position of the vulvar scale ( Fig. 13 ).

Remarks. The holotype was not seen, but is described as a large, pale specimen from Mauritius, conforming with the diagnosis. As morphological and geographic proximity suggest, Hemicordulia populations on Mauritius and Réunion are closely related. The extreme difference in coloration makes separation straightforward and warrants recognition at the species level. Similar differences separate Micronesian species (e.g. Buden & Paulson 2003). All specimens listed by Fraser (1949; 1950) were re-examined, and inconsistencies between my Fig. 13 and Fraser’s (1949) illustration of the vulvar scale and S9 (where the segment is very short) result from a degree of variability in this structure and Fraser’s inaccurate depiction thereof.

Range and ecology. Endemic to Mauritius, where restricted to the mountains in the south-west, which harbour the island’s main forest remnants. It is notable that records are from an altitudinal range of 120 to 680 m ( Mauritius is only up to 823 m high), lower than most sites of its sibling species H. atrovirens . Breeds in pools in rocky streams and rivers, which are mostly forested. Males have been observed patrolling such streams in search of females. Adults have been observed from December to June (D. Grand & A. Martens in litt.).

Figures

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.