MORPHOLOGY
External characteristics
Male
Forewing length (mm): 70-95. Wingspan (mm): 115-160.
One of the largest butterfly species known. Forewings: Upperside narrowly black along front margin followed by broadly green, broad band from wing base to outer margin black, also outer margin broadly black, green area from hind margin to cell and in direction of apex to vein 5; underside forewing largely green and yellowish, with black veins, black along front margin, outer margin and hind margin, and a submarginal wavy black band. Hindwings Hindwing, upperside black along inner margin and outer margin, rest golden yellow, partly translucent, narrowly bordered by green (which extends along veins), and three black submarginal dots in a larger green spot; underside hindwing largely golden yellow, green along outer margin, yellowish green along inner margin, submarginal black spots larger than on upperside.
Female
Forewing length (mm): 85-125. Wingspan (mm):140-210.
Very different from male. Upper and underside similar, forewing blackish brown with small, pale, submarginal spots and an extra spot in space 2. Hindwing blackish brown in basal third and along wavy outer margin, rest of wing golden to dark yellow, shaded with brown on upperside.
Subspecies and variation
There is much individual and local variability and up to nine subspecies have been described by various authors, but local variation appears to be clinal rather than broken up in discrete forms, and nowadays only two subspecies are recognised: ssp. goliath from New Guinea and ssp. procus from Seram.
Similar species
Male slightly similar to male O. priamus, but forewing less elongate, and with translucent golden yellow patches on hindwing. Female unmistakable, if only for its size.
source: Jan Moonen, peronal communication 2020