Thyrassia Butler

Type species: subcordata Walker, India.

Synonyms: Acuttia Kaye (type species bidensis Kaye, Borneo), praeocc.; Atucia Watson (replacement name for Acuttia). The synonomy follows Tarmann (2004).

This genus contains species that bear some resemblance to syntomine arctiines (Holloway, 1988; Tarmann, 2004), but the distribution of translucent patches on the forewing (a medial row of two or three and a subapical one, sometimes divided by dark colour along veins) is not seen in any Bornean syntomines. The narrowly bipectinate antennae in both sexes, strongly developed chaetosemata and complete hindwing venation with two anal veins and CuP present (also in the forewing) are also features not seen in syntomines.

The chaetosemata are large, clearly artonoid, but not extending strongly anteriorly (Tarmann, 2004). Other generic features noted by Tarmann are: reduction of tibial spurs; a triangular uncus completely fused with the tegumen; digitate processes that articulate with the basal part of the valve costa; female genitalia with a short ovipositor and a reduced praebursa. Tarmann (2004) considered that more information was needed to assess the placement of the genus in the Artonini. In the forewing, veins (R2 (R3, R4)) arise as a stalked system from the cell, the rest arising independently (Hampson, 1892).

Piepers & Snellen (1902 [1903]) described the biology of T. procumbens Snellen (Java, Sumatra), a species very similar in facies to bidensis Kaye (see below), but with a more extensive pale subapical area to the forewing, crossed by three veins instead of just one (also rafflesi Moore from Java and Bali). The larva

is dorsally and laterally a deep ochreous yellow, the underside being paler. There are white hairs on the flanks. There are several large dark brown spots on T1, smaller ones on T2, and only a pair of small ones on T3. Each abdominal segment has two large subdorsal patches, and two further ones down each side, declining in size. These are very dark brown except for the subdorsals on A1, A3, A6 and A7 which are paler, nacreous. This larva matches a small sketch associated with the series of the type species in the BMNH collection, so these features may be generic. The grey silken, tissue-like cocoon is formed within leaves.

The host plant given by Piepers & Snellen was Vitis (Vitaceae). Jordan (1907, Gross-Schmett. Erde, 10: 51) and Tarmann (1992b) also noted the larvae as feeding on Vitaceae (Cissus, Vitis); these records were reproduced by Robinson et al. (2001).