[2][3] Among the largest and most gaudy of the Ceylon Lepidoptera is the great black and yellow butterfly (Ornithoptera darsius, Gray); the upper wings, of which measure six inches (15 cm) across, are of deep velvet black, the lower, ornamented by large particles of satiny yellow, through which the sunlight passes, and few insects can compare with it in beauty, as it hovers over the flowers of the heliotrope, which furnish the favourite food of the perfect fly, although the caterpillar feeds on the aristolochia and the betel leaf and suspends its chrysalis from its drooping tendrils.

[4] From Troides helena cerberus it differs as follows: Male forewing: adnervular pale streaks not prominent on the upperside, more distinctly marked on the underside.

Cylindrical, dull purple brown, with two dorsal rows and anterior and lateral rows of fleshy tubercles, those on the eighth segment and a streak from its base to lower end of seventh segment being pale pink; between the tubercles are dark brown streaks.

Pale purplish ochreous, bent backwards anteriorly; thorax conical, the top flattened and its sides angled; wing cases dilated and flattened laterally in the middle, their outer edge acute; two middle segments of abdomen with a dorsal pair of conical prominences.

The primary habitat is thinly wooded mountain forests from sea-level up to an elevation of 2,000 metres.