The Throana group of genera
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Throana Walker

Type species: amyntoralis Walker, Borneo.

This genus contains a number of smallish, slender, delicate species with centrally angled, crenulate margins to fore- and hindwings. Most are shades of grey or brownish grey with irregular darker fasciation, mostly obscure except for the postmedials that are edged by paler lunules distad, that of the forewing usually angled subcostally, with a dark triangle between it and the costa. There is often a broader zone of paler lunules distal to the hindwing postmedial that may incorporate darker, often reddish elements as indicated below. The patterning of the underside repeats that of the upperside. The male antennae are fasciculate or, in one case, bipectinate, but the legs are not densely scaled or tufted. The type species and three others from Borneo where males are known (
klossi Prout, flavizonata Hampson and rufipicta Hampson) have long, slender processes extending from the hindwing dorsum. The second and third segments of the labial palps are very long and slender.

The male abdomen has an elongate eighth segment of the framed corematous type. The uncus is very long, slender, opposed by a slightly shorter scaphium. The tegumen is longer than the vinculum. The valves are rather narrow, tapering.  Both costa and sacculus are thickened to one third. Beyond this, the slender apical  part tapers away, but with a distinctive reflexed barb on its margin where it abuts the sacculus. The aedeagus vesica may be large, with fields of cornuti (e.g.
flavizonata Hampson), though in most species it is small and unornamented.

In the female, the ostium is associated with the eighth segment at its anterior, this being drawn further anteriorly ventrally into the position of the seventh sternite, which appears to be absent. The posterior margin of the eighth segment is consequently deeply cleft. The ductus is slender, sclerotised, slightly fluted. The corpus bursae is small, ovate to spherical, without ornament.

The genus is diverse in Sundaland, with at least three species in Sulawesi, and outlying species in Seram and Australia. However,
Egnasia species from Africa such as rufifusalis Hampson and scotopasta Hampson have similar facies and may be better placed in Throana.

An Indian species,
T. pectinifer Hampson, a much smaller species than those described below, was reared by Bell (MS) and Gardner (1947) in India. The prolegs of A3 are absent, and those of A4 are slightly reduced. The head is greenish yellow with a rosy brown, tesselated band laterally. The body is bright grass-green, with indistinct yellow lateral, supra- and subspiracular lines. The segmental divisions have coalescent rose-coloured spots dorsally, and the segment margins have a yellowish tinge. The solitary larvae live under mature leaves, eating from the edge and skeletonising them. Pupation is in a slight but roomy cell of silk formed within a concavity of the leaf. The pupa is attached to the cell by the cremaster.

The host plant is Adina (Rubiaceae), and Yunus & Ho (1980) recorded a further unnamed species in the genus from Mitragyna in the same family (Robinson et al., 2001).

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