Male. Very closely resembles Byasa latreillei male, but judging by a single specimen the fore wing is proportionately rather narrower, the termen more oblique, the tornus more rounded. The markings on the hind wing differ as follows: the discal white patch composed of four elongate spots in interspaces 2-4, that in interspace 4 very broad, filling the interspace between the middle of veins 5 and 6; subterminal series of lunules larger than in latreilli, and all vermilion-red, not crimson, both on the upper and undersides; cilia between tornus and apex of vein 3, apex of tail aud cilia at apex of vein 5 vermilion-red. On the underside, the spot of the discal patch in interspace 1 is vermilion-red, and the red lunule of the subterminal series in interspace 2 is produced to the vermilion-red terminal edging below it. Antennas, head, thorax and abdomen as in Byasa latreillei.
Female. Appears to differ only from the male on the upperside of the hind wing in the white patch, which is continued posteriorly to the ahdominal margin or nearly so and does not extend into the end of the cell.