Butterfly Uses Eyespots to Deflect Attacks

A species of butterfly uses its eyepsots to perfect the art of "made you miss!" when trying to save the best of itself from predators, underpinning what a research team calls the first experimental evidence that colors and patterns can be used by an animal to trick its most likely predators into attacking its non-essential parts instead of its more vulnerable areas.

In a new study, a team of researchers from Oregon State University, Yale University and four other institutions says it has documented such behavior by observing a species of butterfly called Bycyclus anyana and its distinctive wing shapes, or eyespots.

"Eyespots are conspicuous, they draw your attention and are thought to be used by many animal species to avoid death or attack, by either startling or confusing the predator," explained Katy Prudic, the study's lead author, in a release. "Many insects have eyespots, which suggests they are an important adaptation," the researcher from Oregon State University added.

Bycyclus anyana cranks out five generations a year across both wet and dry seasons. It has a neat genetic trick up its sleeve: It can make two different eyespot patterns from the same genes. This handy feature allows it to use different looks for the wet and dry seasons, when different predators will need to be fooled by different patterns.

In the wet season, the resourceful butterfly creates big, bright eyespots -- the better to fool typical predators of the moment, such as praying mantids, into attacking the bright spots on the wings instead of the head or body.

This comes at a gruesome cost, of course. The butterfly's wings are likely to be badly damaged in an attack, but the made-you-miss trick at least gives it a chance to escape and live to procreate another day.

In the dry season, meanwhile, the butterfly sports small, dull eyespots (see photo above). Most insect predators are dead at this time, but birds are still a threat. The butterfly's drab appearance can help it avoid becoming a meal, because birds have a harder time detecting it.

"Having the right type of eyespot in the right season allowed the butterflies to live long enough to lay eggs and have more offspring in the next generation," said Prudic. "With the wrong eyespot at the wrong time, they were quickly annihilated by the mantids."

The idea of colors, patterns and eyespots being used for protection against predators isn't new to science. But such changes have been difficult to observe and document in a controlled fashion, the researchers say. Their findings have just been published in the Proceedings of the Royal Society B.

From Discovery News