text: The distinctive patterns on butterfly wings really do help protect the insects by mimicking the eyes of predators. While scientists have long suspected the role played by eye-spots found on the wings of many butterflies were an example of mimicry, it has never been clearly tested. Recently researchers suggested that the eye spots may simply scare away predators by confusing them or overloading their senses. Owl butterflies (left) have eye spots that mimic those of pigmy owls (right) to scare off predators like great tits. While scientists have long suspected the role played by eye-spots found on the wings of many butterflies were an example of mimicry, it has never been clearly tested . But a new piece of research by biologists at Jyväskylä University in Finland claims to have settled the debate. They say that eye-spots on the wings of butterflies do in fact mimic the eyes of larger and more threatening species, like owls. Having bright colours and distinguishing features is a common way for insects to scare away predators like birds. Often they help to lure them away from vital body parts or confuse them. However, this only works on predators that hunt using sight while bats tend to be immune to such devices. Now scientists have found that a moth has an unusual evolutionary adaptation that allows it to confuse the ultrasound used by bats. The luna moth has two tails that extend for more than an inch beyond its body. Scientists in the US showed that these appendages produce a confusing acoustic signature in the bats echolocation. It makes the bats target the end of the tails rather than the moth itself. This helps to keep other birds that might normally eat the insects away. The team were finally able to test the theory by showing great tits pictures of owl butterflies that had been digitally altered, and watching their reaction. Images where the eye spots had been removed from the butterfly wings did not stop the birds from snatching a mealworm snack below the picture. However, when pictures that had not been digitally altered flashed on the screen, the birds were more weary. And the researchers found the butterfly eye spots may even be more terrifying to the great tits than the real animal they are mimicking. When shown pictures of a pygmy owl with its eyes open the tits reacted strongly and kept away, but their reaction was not as strong as with the butterfly markings. Writing in the journal Proceedings of the Royal Society B, Dr Johanna Mappes and her colleagues said: 'In this study, the presumed model - owl eyes - and the mimic eyespots appeared to elicit similar reactions both in terms of response type - interest versus aversion - and its intensity - startle versus flee - adding support to the eye-mimicry hypothesis. The researchers flashed up digitally manipulated images of an owls face and the owl butterfly to see how great tits reacted. In some images they removed the owls eyes (far left) or removed the eye spots (far right) Eye spots are a common feature on butterfly wings, like the Bycyclus anyana butterfly above, but scientists have been divided over whether they were intended to mimic other predators or simply confuse predators . 'Predator-prey interactions in nature often involve dynamic encounters between the partners, and eye spots are more likely to appear suddenly in front of the predator. 'Their intimidating effect has been proved to increase when they are revealed abruptly. 'We therefore conclude that it is unlikely that the adaptive value of eye spots is due to sensory or information overload caused by the conspicuousness of colour pattern.' The researchers conducted their experiments by placing wild captured great tits into a cage where the floor had been fitted with a computer monitor. The birds were offered a dead mealworm and as they approached an image was flashed up on the computer screen. Images of owl eyes caused the birds to be startled, flee and in some cases give off alarm calls. but images of owls without eyes did not produce the same reaction. Atlas moths (above) have colourful patterns on their wings that are thought to mimic the head of a cobra . A cobra poses a far greater threat to a predator than an Atlas moth and so by mimicking the reptile with the patterns on its wings the moth is able to scare off potential hunters that might make it a tasty snack . However when the birds were shown images of the owl butterfly, they were also scared away. If the irises of the eye spots were removed, or the eye spots removed altogether, then they were scared away far less often. Many species of butterfly have eye-spots as part of the pattern on their wings. The Atlas butterfly, for example, has a pattern that looks like the head of a cobra. Some entomologists have also claimed that the Eyed hawk moth look like the head of a fox when viewed from the front. In one extreme example of mimicry, the caterpillar of the Eastern tiger swallowtail looks like a snake and spits a foul smelling chemical to keep away predators. Last year scientists at Oregon State University looked at the butterfly Bycyclus anyana and showed that it varies the intensity of its eye spots depending on the season. They claimed bright colours in the rainy season allowed the butterfly to confuse the dominant predators - preying mantids - while duller colours in the dry season helped them hide from birds. Some entomologists claim the eyed hawk moth looks like the face of a fox or dog from the front . The wing patterns of the eyed hawk moth is said to resemble the dark nose and the light coloured eyes of a fox .
target: Biologists at Jyväskylä University in Finland studied how wild great tits reacted to images of the wings of butterflies and the faces of owls .
  The tits were startled and tried to flee at the sight of owl faces with open eyes, and butterflies that had eye spots on them that mimiced owl eyes .
  They say their study is evidence that butterfly eye spots mimic predators .
  Scientists have long debated whether butterfly eye spots were an example of Batesian mimicry or if the patterns simply served to confuse predators .