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Euchromia Hubner
Type species: sperchius Cramer (= guineensis Fabricius; W.
Africa).
Synonyms: Hira Walker (type species sperchius
Cramer); Phalanna Walker (type species polymena Linnaeus;
Oriental).
The wing venation is as illustrated (Fig. 1). The antennae are
moderately bipectinate in both sexes. Both wings have antemedial and postmedial
blocks of pale colour, traversed by veins that are dark brown or blackish - the
ground colour of the wings. The pale patches are white or yellow. There is a
pale blue lunule at the end of the forewing cell between the major areas of pale
colour. The abdominal segments are ringed with blue and yellow, orange or red.
The male genitalia have simple valves, a broad, divided juxta, a short,
broad uncus set on a rather shouldered tegumen. The aedeagus vesica is unadorned
though its membrane may be irregularly thickened on one side.
In the female genitalia there is a massive ventral gland associated with
the ovipositor lobes as well as the usual dorsal ones. Segment eight is weak,
narrow, with short apodemes. The ductus bursae broadens out to the width of the
abdomen at the ostium. The bursa has a distal spherical portion that is densely
and darkly scobinate, and a basal tubular portion that contains three robust,
spined bands of sclerotisation; there is an appendix bursae just basal to these
bands.
The larva and cocoon of polymena were described and illustrated
by Horsfield & Moore (1858-1859), and Bell (MS) also described the early
stages. In both cases the host-plant was Ipomoea (Convolvulaceae). The
eggs are laid in batches on the underside of leaves. They are smooth, shining,
spherical, honey coloured. The larvae are gregarious, only separating when
almost fully grown. The body of the larva is cylindrical, with long dorsolateral
pairs of hair pencils on T2 and T3 (directed forwards) and on A9 (directed
dorsolateral backwards). On each segment in between there are verrucae typical of Arctiidae,
bearing long hairs below the level of the spiracles, and heavy, close-packed
tufts of much shorter, pectinate setae in a coalescent band transversely across
each segment above the level of the spiracles. The general body colour is
brownish orange; the transverse bands of tufts are laterally black but dorsally
buff, except on A1 and A8 where they are all black.
The rounded cocoon is spun between leaves in a crevice of bark or on any
surface. It fits the pupa closely, and the short setae from the transverse tufts
are embedded in it, erect, carpet-like. The cocoon is surrounded by a fence of
the black setae from the tufts.
The genus is represented in Africa and the Oriental Region by species
with yellow patches, except for one with white patches in Sri Lanka. There is
one species with yellow patches in New Caledonia. Within the Australasian
tropics is a large complex of species with white patches; there are
representatives of this complex in Sulawesi and the Palau group.
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