A Courtesan conundrum

Found a new female form for KS today (the third). However, it has caused more problems with this species. Note the following:

THAILAND: Subspecies, E. nyctelius nyctelius,5 female forms - cinnamomea, alcathoeoides, euploeoides, nyctelius and isa.

MALAYSIA: Subspecies, E. nyctelius euploeoides, 2 female forms - euploeoides and isina.

The form I saw today, pictured below is female f. isina! It differs only slightly from the known Thai form f. isa, but lacks the submarginal white spots on the upperside hindwing (though they are present on the underside).

Have I found a new female form for the Thai ssp. or new ssp. for the Thai records? Or are the two forms actually synonymous in which case I'm getting excited for nothing?

I've always wondered how this butt got its name.:hmmm: :bsmile: