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Butterfly eyespot. Close-up of the hindwing of the owl butterfly (Caligo illioneus), showing an eyespot. Owl butterflies (family: Brassolidae) are so called for their wing eyespots which resemble the eyes of an owl. One such eyespot occurs on the underside of each hindwing, and they are hidden from view until needed. They serve to startle and frighten an attacker when they are flashed suddenly at the predator. This display would also draw the attacker's attention away from vulnerable parts of the butterfly's head. Small overlapping scales produce the colouration and patterning on the wings. (KEYSTONE/SCIENCE PHOTO LIBRARY/NIGEL DOWNER/SCIENCE PHOTO LIBRARY)