Owl butterfly
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 Owl butterfly (Caligo memnon)
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Owl butterflies, of which there are 21 different species, are members of the genus Caligo, in the family Nymphalidae ( subfamily Morphinae, tribe Brassolini ), and are found in the rainforests and secondary forests of Central and South America.
The name is derived from the presence of large "false eyes" ( ocelli ) on the underside of the hindwings. It has been speculated that these eyespots and the general patterning combine to give the butterfly the appearance of an owl, and that this functions to scare smaller birds that may prey on it, but there appears to be no evidence to support this theory. The owl-like appearance is only apparent when the wings are spread flat and viewed from the underside, with both hindwings visible to the viewer, but the butterfly always settles with it's wings closed, showing only one of the eyespots, and does not under these circumstances look remotely owl-like.
It is far more likely that the eyespot acts as a decoy, diverting bird attack away from the vulnerable body, and towards the outer part of the hindwings. This use of decoy eyespots is well documented and used by a large number of butterfly species. These decoys can, as in the Owl butterflies, the Grayling and the Gatekeeper take the form of eyespots; while in other species such as Hairstreaks they can take the form of lines, bright spots or even "false antennae" on the wings, all functioning to divert bird attack away from the butterfly's body.
Owl butterflies are very large, and fly only a few metres at a time, so avian predators have little difficulty in following them to their settling place, which is nearly always on a tree trunk. Once settled however the mottled patterning of the butterfly enables it to be superbly camouflaged against the tree trunk, with only the eyespot remaining prominent. Birds do not aim their beaks aimlessly - they try to aim for the body of a butterfly, but when the butterfly is well camouflaged they would aim instead at the most obvious and prominent feature, which in the case of Owl butterflies is the eyespot. This decoy theory is supported by may observations of Owl butterflies that have large chunks taken out of their hindwings ( butterflies are able to fly and go about their lives normally with even quite large chunks missing from their wings ).
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