Sepedon spinipes

Elberg, Kaupo, Rozkošný, Rudolf & Knutson, Lloyd, 2009, A review of of the Holarctic Sepedon fuscipennis and S. spinipes groups with description of a new species (Diptera: Sciomyzidae), Zootaxa 2288, pp. 51-60 : 57

Sepedon spinipes group

The S. spinipes group is characterized by the presence of a few short hairs, a little finer and longer than those on the thoracic dorsum, on the posterior slope of the callus between the posterior thoracic spiracle and wing base on the katatergite (=metapleural callus of authors). Also, Knutson & Orth (2001) characterized this group by the presence of a presutural intra-alar seta (sometimes referred to only as "presutural"). We have examined several hundred specimens of S. spinipes from the Western Palearctic and S. americana from North America. In fact, a distinct presutural intra-alar seta is absent in most specimens. When present, it is at most only twice as long as, and slightly more erect than, the surrounding hairs on the thoracic dorsum.

In this group only one holarctically distributed species with the Palaearctic nominate subspecies and the Nearctic S. spinipes americana Steyskal, 1951 has been recognized. Steyskal distinguished his new subspecies in his key to the American species of Sepedon by presence of the orbital spot, the slightly pruinose and bare middle part of the face, the haired katatergite (more precisely a supraspiracular convexity of the metathorax), the distinctly outwardly bowed posterior crossvein, the mid femur with a strong mid-anterior bristle, and the thickened and concolorous tawny hind femur. These characters are also well distinct in the nominate form of S. spinipes occurring in the Palaearctic region as confirmed by Steyskal (l.c.) in material from France, Greece and Latvia. The only distinguishing character stated by him was the difference in structures of the male terminalia.

The recently re-examined representatives of both “subspecies“ prove that actually there are no external non-genitalic distinguishable characters among both taxa but some major structures of the male terminalia, especially the conspicuously different shape of the aedeagus ( Figs 22, 26 ), are even more different than within members of the S. fuscipennis group ( Figs 12–15 ). The male terminalia structures of S. americana fit well with the original figure published by Steyskal (1951, Fig. 23 ) and are markedly different from any species collected in the Nearctic Region. Therefore the differences found between S. spinipes and S. americana may be considered to be of a specific level in full accordance with the current general concept of species in the large genus Sepedo n. The S. spinipes group as defined by Knutson & Orth (2001) thus does not include only one species with a Holarctic distribution but two different species, the Nearctic S. americana and the Palaearctic S. spinipes .

Figures

FIGURES 20 – 27. Species of Sepedon spinipes group, male terminalia. 20 – 23. S. americana. 24 – 27. S. spinipes. 20, 24. Lateral view. 21, 25. Hypandrium in lateral view. 22, 26. Aedeagus in lateral view. 23, 27. Epiphallus in caudal view. Scales: 0.5 mm (Figs 20, 24), 0.3 mm (Figs 21 – 23, 24 – 27).

FIGURES 8 – 19. Nearctic species of Sepedon fuscipennis group, details of male terminalia. 8, 12, 16. S. floridensis. 9, 13, 17. S. fuscipennis. 10, 14, 18. S. gracilicornis. 11, 15, 19. S. tenuicornis. 8 – 11. Hypandrium in lateral view. 12 – 15. Aedeagus in lateral view. 16 – 19. Epiphallus in caudal view. Scale: 0.3 mm.