Orgyia osseata Walker, 1862, J. Linn. Soc. (Zool.), 6:125.
Orgyia dimidiata Walker, 1862, J. Linn. Soc. (Zool.), 6:125,
Rilia basivitta Walker, 1865, List Specimens lepid. Insects
Colln Br. Mus., 32: 436.
Diagnosis. This is a very variable species as illustrated. It has much narrower
wings than postica, and the forms with grey or red zones along the costa,
or with pale cream lineation are distinctive. The more typical brownish form can
easily be confused with the next species. This can be distinguished primarily on
male genitalia. The key feature is not so much, as suggested by Schintlmeister
(1994) (who illustrated several specimens of osseata as araea: figs 26-29), presence or absence of a small angular process in the centre of
the valve costa, just subbasally on the dorsal arm, but a short (osseata) versus
long (araea) digitate process on the juxta. It is osseata, rather
than araea, that has the angular process on the valve costa, though this
is variable in development. The females of both species are winged, that of osseata
(illustrated) having strong blackish marks costally and subdorsally,
adjacent to the forewing postmedial.
Geographical range. Indian Subregion, S.E. Asia, Sundaland, Philippines.
Habitat preference. Most records are from lowland forest, disturbed and
cultivated areas, where the species is frequent. It has been taken rarely up to
Biology. Bell (MS) described the larva in S. India. It has the hair-pencils and
dorsal brushes typical of the genus. The brushes are whitish, grading pale
yellow towards the centre. The body is light green with pinkish dorsolateral
bands, the verrucae within the latter being of the same colour. There is a
dorsal black patch between A1 and A2, and a smaller one at the anterior of A3.
The head is pale red, and the prothoracic collar is pink.
The larva has a wide host range, including Mangifera (Anacardiaceae),
Averrhoa (Averrhoaceae); Durio (Bombacaceae); Dryobalanops,
Shorea (Dipterocarpaceae); Acacia (Leguminosae), Eugenia (Myrtaceae);
Ixora (Rubiaceae), Nephelium (Sapindaceae); Sonneratia (Sonneratiaceae)
and Theobroma (Sterculiaceae) (Murphy, 1990; Kuroko & Lewvanich,
1993; unpublished IIE and FRIM records; S. J. Willott, pers. comm.).
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