According to Dr. Keith Willmott, assistant curator of Lepidoptera at the McGuire Center for Lepidoptera & Biodiversity in Florida and a leading expert on South America butterflies, this is a Taygetis species, possibly Taygetis larua or Taygetis mermeria, or another possibly undescribed species near to both of these.
Dr. Willmott informed me that it's difficult to tell without a good look at the underside of the wings.

Reserva Ecologica Taricaya, Puerto Maldonado, Peru, 22 June 2009