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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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