MORPHOLOGY

External characteristics

Male
Forewing length (mm): 68-79. Wingspan (mm): 116-138.
Forewings: Upperside black, indistinct to inconspicuous paler double stripes between the veins in outer half of the wing; underside similar. Hindwings crenulate, broad, more or less spatulate tail at end of vein 4 tail; upperside black, dirty blue double stripes between the veins in outer half of the wing, may be much reduced; underside black, pattern very variable, from very indistinct dirty violet submarginal and bluish median spots to blue double stripes as strongly developed as on upperside with some indistinct dark red submarginal dots, to blue stripes reduced in length, but with conspicuous red submarginal spots,

Female
Forewing length (mm): 76-82. Wingspan (mm):128-143.
Forewing, upperside lack with conspicuous whitish, pale ochreous or pale violet-brown stripes on both sides of the veins (i.e. double internervular stripes), almost solid dark brown to black along outer margin; underside as upperside. Hindwing, upperside dark brown to black, dark red submarginal spots in spaces 1b to 7, central part of wing inconspicuously paler with violet flush, or more conspicuous and whitish or very conspicuous and pale ochreous, covering area from vein 1b to almost vein 7, including outer half of cell.

Subspecies and variation

Individual variation is considerable as described above. The nominate subspecies is found on Sulawesi. The populations of the Sula Archipelago have been described as ssp. ascalon; it is the smallest and darkest form of the male.

Similar species

Nearly as dark as P. acheron, but not easily mistaken, as the two species do not fly together.

_{source: Jan Moonen, peronal communication 2020}