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Diomea Walker

Type species: lignicolora Walker, Sri Lanka.

Synonyms: Corsa Walker (rotundata Walker, Sri Lanka); Zigera Walker (type species: orbifera Walker).

The above synonymy, originally suggested by Yoshimoto (1994) and formalised by him later (Yoshimoto, 2001a), brings together genera that typically have a more uniform, less irregularly ligneous forewing pattern and usually on the hindwing a diffusely paler postmedial fascia that is often only evident as an angular mark at the dorsum, but is more continuous in
orbifera. There is a diffuse, irregular pale submarginal on fore- and hindwings in many of the species. Features of the male abdomen are also uniform through most of the genus. Poole (1989) placed Zigera as a synonym of Diomea, but Corsa has page priority over the latter. This was overruled by Yoshimoto (2001a) as first reviser.

In the male abdomen the eighth segment is typical of this fungus-feeding group. In the genitalia the tegumen has a distinctive shape, narrow on each side, with a lapel-like edge that terminates ventrally in a slight interior angle. The valves are long, narrow, distally tongue-like. The sacculus ends in a curved spine at the ventral margin, usually with an oblique, setose ridge of sclerotisation running basad from the base of this spine towards the base of the valve costa. There is a distinct saccus. The aedeagus vesica is small, with some diverticula.

The female genitalia have a small but typical appendix bursae, the ductus being similar to that of
Drepanorhina, with an oblique ostium, though without a central angle. The corpus bursae is immaculate.

The biology of the type species of Corsa and Diomea is described below. Mutuura et al. (1965) illustrated a Japanese species stated to feed on the polypore Polystictus.

The genus is most diverse in the Oriental tropics but extends weakly to New Guinea and the Solomons. Diomea fenella Robinson from Fiji is misplaced, having male genitalia with valves with a narrow apex flanked by a very long, narrow costal spine and a much narrower, clublike saccular process. In these features it resembles much more closely the Australian Artigisa impropria Walker, a species that Edwards in Nielsen et al. (1996) suggested might be better placed in Sandava Walker (see p. 375).

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