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Gadirtha
pulchra
Butler
Gadirtha pulchra Butler, 1886, Trans. ent. Soc. London, 1886: 412.
Hypogramma
distincta
Lucas, 1892, Proc. R. Soc. Qd, 8: 86.
Diagnosis. The forewings are grey with rather Cossus-like
reticulation and fine black transverse fasciae subapically and subbasally. The
reniform is also finely ringed black. The hindwings are whitish, graded to dark
grey-brown at the margin, the veins also being delineated darker.
Geographical range. Indian Subregion, Ryukyu Is., Thailand, Singapore,
Borneo, New Guinea, Queensland.
Habitat preference. Only a single Bornean specimen has been seen, from the
lowlands of Sarawak near Kuching.
Biology. Bell (MS) and Murphy (1990) reared the species in India and
Singapore respectively; Murphy illustrated the larva in colour. The larva is
depressed, cylindrical in shape, somewhat broader centrally and highest at T3.
All prolegs are fully developed, the end ones splayed out behind the body. The
head is round, light orange, reticulated darker, and with short black setae.
Only primary setae are present, set on glossy tubercles, but some of these are
hair-like, as long as the body is wide. The colour is grass green with a broad,
pulsating, violaceous dorsal line, within which are black, roundedly oval spots
1mm in diameter, ringed paler, one at each of the anterior margins of segments
T2 to A8, declining in size from A1 backwards, often absent posterior to A5
(illustration in Murphy (1990)). There is a narrower, bright yellow dorsolateral
band, and weakly defined supra- and subspiracular lines of light yellow.
The pupa is oval, with the venter flat, broader than high over the anterior
half. The three posterior segments are conjoined, depressed dorsally, apically
broadly blunt and upturned with the anterior margin of A8 dorsally humped, the
two humps having a beaded transverse ridge anteriorly. The head lacks a
proboscis.
The larvae live, often gregariously, on the undersides of leaves of the host
plant, eating voraciously and growing rapidly. The cocoon is of silk
incorporating bark particles, oval, lowly convex, yellow brown to grey in colour.
When touched, the pupa shivers inside the cocoon wrapping the abdomen, making a
rustling sound. There is no indication of whether the beaded ridge is involved
in this.
The host-plants recorded by Bell were Sapium and Excoecaria (Euphorbiaceae).
Murphy (1990) recorded the latter as host in mangrove habitats, and it has also
been noted in the Andaman Is. (unpublished IIE records).
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