Adelpha boreas, the Gaudy Sister or Solitary Sister, is a butterfly of the Nymphalidae family. It was described by Butler in 1866. It is found from Costa Rica to Bolivia. The habitat consists of primary and disturbed rainforests and cloudforests at altitudes between 200 to 1,200 meters.The wingspan is about 47 mm. Adults have been observed imbibing moisture from damp ground.The larvae feed on Satyria species. Young larvae feed on the leaf tips, constructing a chain of frass along the midrib.