This subspecies is distinguished from all species with which it is sympatric by the presence of a prominent, subapical, costal, grey patch on the forewing, with a grey streak posteriorly on vein M1; and by the sharply defined distal border of the hindwing. Tegula with a grey fringe in fresh specimens. Abdomen upperside with 2 dark dots at the bases of segments 3 and 4; anal tuft dark, the tip often paler, wine red rather than yellow or brownish orange. Forewing upperside with lines not prominent, the spaces grey; a grey streak on vein M1 and the grey costal area anterior to it both prominent; a black apical chevron joined to the submarginal patch in cell Rs4, which is black distally and russet proximally; subapical patch in cell Rs3 russet. Both wings undersides brown, shaded with khaki, the yellow anal area contrasting sharply. Hindwing upperside yellow band very sharply defined, the costal margin not yellow.
Male genitalia: Uncus similar to that of Macroglossum glaucoptera, but rather more flattened apically and less truncate-sinuate. Valve with prominent stridulatory scales. Harpe with a very short triangular, tapering, free process, but longer than in Macroglossum prometheus lineata. Phallus without teeth near the base of the process; process with a single basal tooth that points distad, and a number of teeth on and near the proximal edge, unlike Macroglossum prometheus lineata.
The record for Sri Lanka is based on a single specimen in NHMUK and the presence of Macroglossum prometheus on the island needs to be confirmed. There are specimens in CMNH from SW India that are identified as this species but this needs to be reconfirmed.