Imosca megastigmata
Hampson (Plate 2, Figs 35, 48)
Borsippa megastigmata Hampson, 1894, Fauna Br.
India, Moths, 2: 518.
Allocosmia
sugii Kobes, 1984, Heterocera
Sumatrana, 2: 29, syn. n.
Diagnosis. See the generic description.
Taxonomic note. The male genitalia of megastigmata
are almost identical to those of sugii illustrated in the original
description. However, the material reared by Bell in S. India (see below) has
the costal dark patch much narrower than in typical megastigmata, and
the subtornal markings are absent; the posterior part of the postmedial pale line
is less oblique.
Geographical range. Indian Subregion, Sumatra, Borneo,
Peninsular Malaysia.
Habitat preference. Two specimens have been taken in the
canopy of dipterocarp forest at 170m near the Danum Valley Field Centre, Sabah
(S.J. Willott, unpublished data).
Biology. The larva was described by Bell (MS) and
Gardner (1948a; only tentatively identified as megastigmata), is
elongate, with constricted segments. The prolegs on A3 and A4 are reduced to
small cylinders. The crochets are appendiculate. The head is relatively large,
broader than high, granulate and shallowly bilobed, the setae arising from
chalazae. The colour of the larva is a light translucent green, glaucous
subcutaneously. On the body there is a darker, fluctuating dorsal band bordered
on each side by finely wavy or broken white lines. There is a more distinct,
broken, yellow dorsolateral line and an even more fragmentary spiracular one.
The dorsolateral line can be tinged with pink in places. The head is also lined
and more generally tinged and spotted with
yellow.
The larvae live
on the undersides of youngish leaves, eating from the edges irregularly, and
are active, restless, with a leech-like motion. They squirm and jump like fish
when intensely alarmed. Pupation is in the soil in a strong, ovoid, silken
cell. The host plants are as stated in the generic account.
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