Malagasy Dotted Border (Mylothris phileris) is a medium-size butterfly in the family Pieridae.
It is endemic to Madagascar.
Glossary of butterfly terms: https://butterfly.ucdavis.edu/resources/glossary
About 6 cm long plus a 3 cm tail (it dropped the tail when my cats chased it on the porch - they may have brought it in from outside). Dark silvery gray on top, lighter belly. Thrashing around a lot, couldn't tell if it was using its limbs or if they were kind of vestigial
Mole River, Mole National Park
At least the genus should be reliable.
Could be B. phantasina too
Found dead on the path