Thanks to Kim Garwood the true identity of this butterfly has been discovered; it is Arawacus tarania Tarania Hairstreak; at Pousada Rio Azul (in the white-sand campasina scrub), Para, November 15 - 19, 2008. It is classed by K.S. Brown as a Cerrado specialist - but this individual was found in a patch of campasina within the forest belt in southern Para state, and as such may be a range extension; CLICK HERE to visit the BOA account for this taxon:
