The evolutionary significance of butterfly eyespots

Numerous butterflies have circular patterns called eyespots on their wings. Explanations for their functional value have until recently remained hypothetical. However, several studies in the last few years have supported long-standing hypotheses, and the current paper reviews these recent advances. Large and conspicuous eyespots are thought to be effective by being intimidating to predators and thus reducing predation. This hypothesis has received strong support in different studies. It has been shown that eyespots are intimidating because of their conspicuousness, but experimental support for the idea that eyespots are effective by mimicking vertebrate eyes is at the moment lacking. Studies have also tested the deflection hypothesis, where smaller marginal eyespots are thought to deflect attacks away from the body of the prey, increasing chances of survival with a torn wing. Despite previous negative results, recent work has shown that eyespots can indeed deflect attacks toward themselves under specific conditions. Furthermore, data show that dorsal eyespots are used by males and females as signals during courtship. How the diversity in ventral eyespot patterning has evolved remains a mystery. Future directions and further challenges in understanding the adaptive value of eyespots are discussed. Copyright 2011, Oxford University Press.