This strange butterfly is a member of the family Lycaenidae; one usually associated with blues, coppers and hairstreaks. There are however, a group of butterflies in the subfamily Miletinae which are rather different from other members of the family. They have strange and rather off-putting names, Brownies and Darkies, but are rather elegant and well camouflaged butterflies. Some species of Allotinus butterflies are myrmecophilous, which is a rather posh way of saying that they live with ants! Or at least they have some form of symbiotic relationship with ants or ant nests.
There are different dry and wet season forms in this species; in the dry season form, the forewing has a sharp point – which can be seen in the above two photographs taken in February in Thailand – and a lobe at the corner (tornus) of the forewing (hidden by the hindwing). Another photograph – taken in the same area in early May (shown below) – shows a female with a much less pointed forewing, presumably more indicative of the wet season form.