Philaethria dido dido
This large, gorgeous butterly has a wingspread of a little over 4", and the chartreuse green markings seem to glow as they are almost translucent. They were relatively tame, approachable to within a few feet.
These were spotted on the north bank of the Amazon River about 30km downstream from Iquitos, sipping from wet mud next to a boat landing. The surroundings were semi-cleared, the site of a sugarcane mill (small scale, using horses) and still fairly wild.