The Horsfield's Baron (Tanaecia iapis puseda)
The male Horsfield's Baron is territorial, and often displays a behaviour where it perches on a few preferred vantage points and then fly out to "attack" anything that intrudes into its territory. The characteristic dark brown/black wings with a light blue marginal border across both wings up to the termen of the forewing sets it apart from most butterflies in Singapore. Beginners, however, often confuse this species with the male Archduke & Black Tipped Archduke, which are larger and feature a more robust body. The underside of the Horsfield's Baron is pale buff with light brown markings.
Male Horsfield's Barons are seldom encountered puddling or feeding on fallen fruits in the forest. ButterflyCircle member Loke PF's shot is one such instance where this male was so intent on feeding on what appears to be a rotting fruit that it stayed in the same position for a long time.