Butterfly wing patterns may put predators off target

Researchers have found that butterfly wing patterns can create misleading motion signals in flight, a visual trick that may help these conspicuous insects escape predators.

The study, published in Nature by a team from the universities of Exeter and Essex, combined high-speed filming, computer modelling and touchscreen tests. The researchers examined wing patterns from 397 European butterfly species.

One striking clue came when a computer model of bird vision interpreted a butterfly flying upwards as moving downwards. As wings bend, fold and change angle, their markings can send visual signals that conflict with the insect’s true direction.

To explore whether those illusions could disrupt an attack, 100 volunteers made 3,000 attempts to catch virtual butterflies by tapping a screen. Patterns predicted to create stronger visual confusion caused people to aim farther behind the butterflies. Such errors could make a predator miss altogether or strike a less vulnerable part of a wing rather than the body.

The study did not test attacks by live birds, so the effects on hunting in the wild remain to be confirmed. Not all butterflies appear to use the same strategy: some may depend more on camouflage or colours that warn predators they taste bad. But the findings suggest that standing out need not mean being easy to catch.