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Tristeirometa Gen. n.

Type species: bostryx Prout.

This genus consists of species assigned to the first section of Hypocometa Warren recognised by Holloway (1976). Its removal renders the latter a more natural group: both can be defined principally on characters of the male genitalia. With Phthonoloba Warren, these genera comprise a predominantly tropical montane group that ranges from the Himalaya and Japan to New Guinea, but has perhaps its greatest diversity in Borneo. In all three, the male hindwing has the anal area and vein unmodified, though the wing itself is relatively narrow as in the Sauris Guenťe group. The antennae are similarly filiform, ciliate, and slightly swollen over the distal two-thirds but tapering away at the apex.

The forewings of Hypocometa and this new genus are green in tone, compared with the dark brown and dull orange of Phthonoloba. In Tristeirometa this green ground is brighter, more uniform than in Hypocometa, with the dark brown fasciae more sharply defined and more intensely developed between the antemedial and postmedial fasciae.

The male genitalia provide diagnostic features. The uncus is apically trifid, a feature not seen elsewhere in the tribe. The valves are simple, without saccular ornamentation. The valve costa is rounded at the apex, slightly more setose, the apex very slightly separated from the main lamina. The aedeagus is short, broad, lacking ornamentation. The second abdominal sternite is somewhat as in Trichopterigia but has only a single corema.

The female genitalia have rounded ovipositor lobes. The bursa is pyriform without scobination (bostryx) but narrow in other Bornean species and pleated longitudinally or containing extensive spines.

The genus includes the four Bornean species listed below and the following non-Bornean species from the first section of Hypocometa identified by Holloway (1976): T decussata Moore comb. n. (N.E. India, Taiwan); T benguetana Schulze comb. n. (Luzon, ?Sumatra); T. auxostira Prout comb. n. (S. India).

Sevastopulo (1946, 1947) described the larva of decussata. The head is very slightly bifid. The colour is very variable, tending to match that of the leaves on which it feeds, e.g. yellow-green with a pinkish lateral line on Citrus (Rutaceae), orange pink with intersegmental areas and a faint dorsal line darker, or deep crimson on Rosa (Rosaceae). There are also variants that are green tinged with bronze or green with a crimson and yellow lateral line. The species also feeds on Malus (Rosaceae).

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