Butterflies in the genus Mycalesis, the Bush Browns, are common in the warm regions from Central Asia to Australia.
Predominantly brown in colour, all the species of the Bush Browns have submarginal ocelli (eyespots) on the underside of both the fore and hindwings.
Their flight is generally weak but they are alert and skittish, and are often quite challenging to photograph. 
The Bush Browns typically rest with their wings folded upright.
They are notably polymorphic, with wet- and dry-season forms differing in many species, especially as regards size and number of underwing eyespots.
While the ocelli in the wet-season forms are usually well defined and clearly visible, the ocelli in the dry-season forms are usually faded and small.

The Dark-brand Bush Brown (Mycalesis mineus) looks very similar to the Dingy Bush Brown (Mycalesis perseus).
With the wet-season forms, you can tell the difference between the two by looking at the posterior four ocelli on the underside of the hindwing.
Are they all four in a straight line, then it is Mycalesis mineus.
If only three are in a straight line, it is Mycalesis perseus (the other ocelli are strongly curved outwards).

Mycalesis mineus also looks very similar to the Pachmarhi Bush Brown (Mycalesis perseoides).
The male Mycalesis perseoides differs, however, from Mycalesis mineus by 
the sex-mark on the underside of the forewing, which is longer, broader, and is ochraceous brown, and not black in colour.

Wet-season form. Ben Tre area, Mekong Delta, Vietnam, 23 December 2023