Many butterfly species feature two or four conspicuously coloured eyespots on their wings; the most commonly heard explanation for these markings is that they are used to intimidate predators. However, this explanation has stood, until recently, on the flimsiest of empirical foundations. Now, Adrian Vallin and colleagues have demonstrated empirically the effectiveness of these signals in dissuading avian predators from attacking the bearers. Their work suggests that predators can be intimidated by bold displaying by otherwise defenceless prey, and opens up an interesting challenge to evolutionary ecologists to explain how this apparently maladaptive behaviour is retained in predator populations.