Butterfly eyespots mimic eyes

New research confirms the theory that butterfly eyespots exploit a predator's fear of large eyes.

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Sometimes science gets around to formally testing something that we thought we already knew. It has long been assumed, for example, that the eyespots adorning the wings of many butterflies and moths are designed to deter would-be predators by mimicking the stares of more formidable adversaries.

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However, there’s another possibility. Eyespots might simply startle prospective predators with a sudden flash of bright, contrasting colours rather than mimic eyes specifically.

“Eyespots’ resemblance to eyes is sometimes so stunning that we have forgotten to question its validity scientifically,” says Sebastiano De Bona of Finland’s University of Jyväskylä.

To test these alternative hypotheses, De Bona and colleagues compared the reaction of great tits to computer-manipulated images of butterfly eyespots and the faces of owls. Eyespots proved as effective a deterrent as real eyes, and more so than equally colourful patterns that were less eye-like.

In which case, eyespots do indeed appear to exploit predators’ instinctive fear of big eyes – and our own instincts seem to have been right all along.

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Source: The Royal Society