These two species can be very confusing in Singapore.
It is probable that crossing between the two and the small colonies have results in intermediate forms being common.

There is no comparable forms like the typical hordonia in P. Malaysia, where the grey submarginal band is very broad and the orange band may be obsolete.

P. hordonia P. Malaysia.
Male with broad grey submarginal band/fascia.
https://i.pinimg.com/736x/a0/f2/7c/a...9872e77bfa.jpg
Male with orange submarginal band obsolete.
https://live.staticflickr.com/1549/2...0d2be7e4_c.jpg

Typical male P. sandaka ,Raub.
https://blogger.googleusercontent.co...0/DSC_0137.JPG



PANTO.png
Pantoporia hordonia hordonia
In Singapore the grey band is not that wide but still wider than the orange submarginal band.
The male have a narrower 'foot.
Orange submarginal band may very irregular, much broken, or obsolete.
Male with small HW grey brand.
Males.
https://www.inaturalist.org/observations/195170218
https://www.inaturalist.org/observations/176612087
https://www.inaturalist.org/observations/175183123
https://www.inaturalist.org/observations/141239367
https://www.inaturalist.org/observations/134397329
https://www.inaturalist.org/observations/19657664
Females.
https://www.inaturalist.org/observations/195170191
https://www.inaturalist.org/observations/104523291
https://www.inaturalist.org/observations/81146818
https://www.inaturalist.org/observations/32403114


Pantoporia sandaka sandaka.
In this species the FW grey submarginal band is typically narrower, being hemmed in by the orange bands.
The orange submarginal band is well defined ,more regular and prominent, & not broken up.
However the females of the two can look rather similar.
The male have a larger foot than P. hordonia.
Male with large whitish HW brand.
Males.
https://www.inaturalist.org/observations/256468037
https://www.inaturalist.org/observations/135218837
https://www.inaturalist.org/observations/134397320
https://www.inaturalist.org/observations/86976671
https://www.inaturalist.org/observations/30309158
Females.
https://www.inaturalist.org/observations/140043534
https://www.inaturalist.org/observations/9679604
https://www.inaturalist.org/observations/20177931

TL Seow: Cheers.