MORPHOLOGY
External characteristics
Male
Forewing length (mm): 60-71. Wingspan (mm): 116-135.
Forewings: Upperside black, dark bluish stripes on both sides of veins more or less visible; underside similar, but stripes more prominent and base of cell conspicuously red. Hindwings crenulate, not tailed; upperside black, dark gray, dark violet or dark blue stripes on both sides of veins, more prominent than on forewing, basal third of wing massively black; underside black in basal 3/4, three or four red spots at base, outer third of wing gray, dark gray-brown or reddish with parallel series of submarginal and median spots, which may be so large that the pale color of the outer third is reduced to a lattice, or outer third not paler, reddish mark at margin in space 1b enclosing a rounded black spot and and space 2 enclosing two rounded black spots, starting at the inner side of these spots a narrow band of diffuse, separate blue spots running to apex.
Female
Forewing length (mm): 67-81. Wingspan (mm):112-135.
A bewildering variation, tailed and tailless, various colors and mimicking females of several species of Atrophaneura and Troides. Forewing generally brown with the pale stripes on both sides of the veins prominent and enlarged so that the pale color appears to replace the ground color, while the veins and stripes between the veins are dark; in the apical third the pale color may be so extended that the area is practically white with finely darkened veins; in all forms, base of cell prominently red, sometimes orange or whitish. Hindwing, upperside very variable, from almost entirely black with some vague markings to more or less white or whitish in basal half or outer half, or white replaced by pale and/or warm ochreous, white may cover more than half of outer part of wing and may contain large, separate, black submarginal spots, or outer half black and inner half ochreous with heavily blackened veins; underside similar, always three or four red spots at base which may be darkened and less visible.
Subspecies and variation
In view of its large distribution area (from NE India to Japan, Borneo and Lesser Sunda Islands) the number of 13 recognised subspecies (of which nine in the Malesian area) is not so many. The individual variation within subspecies may also be considerable, e.g. in ssp. memnon (Java and Borneo) females may be tailed and tailles, on the underside of the hindwing the basal half may be white with heavily blackened veins, and black outer half, or the basal half may be black with the outer half white or warm ochreous with blackened veins and large black submarginal spots. Although the variation is large, the tailed females (in the subspecies memnon [Java and Borneo], agenor [Malaysia] and anceus [Sumatra] also tailles females occur), wing pattern is always reminiscent of Pachliopta species, with on the hindwing a smaller or larger white area crossed by dark veins, and a dark outer area.
Similar species
In spite of the bewildering variation the species is not easily confused with other Papilio species. The tailed females are undoubtedly mimics of Pachliopta species, but the similarity is rather superficial, as Pachliopta species have narrower wings and never show the conspicuous red base of the cell on the upperside of the forewing.
source: Jan Moonen, peronal communication 2020