Eyespot markings probably protect insects by disrupting predator behaviour.
When we talk about animal adaptations we are often guilty of anthropomorphism. What I mean by that is that we easily slip into describing things as humans would experience them. We talk of woodlice ‘liking’ damp places, or Kissing Bugs ‘preferring’ human blood, but a moment’s reflection tells us that this is not what we really mean – it is simply a well-understood ‘shorthand’. What we really mean is that woodlice have behavioural responses which lead them to damp places, or that the kissing bugs have evolved mechanisms which increase the chances of them feeding on human beings. There is little harm in this, as long as the ‘shorthand’ is understood for what it is.
Things become more complicated when we talk about adaptations like the eyespots often found on the wings of insects. Do they really ‘scare’ predators? Or do they ‘evoke responses’? If you try the following link (Don’t try this link if you have a heart problem!) – you might well have a reaction that you could describe as ‘scared’, but do you really think there is anything inside your computer that could harm you? I would suggest that our reactions to images are in some ways (initially at least) similar to the reactions of other creatures. Evolution equips animals with ‘hard-wired’ responses that aid survival.
Predators respond immediately to eyespots because they are ‘wired’ to behave in that way. They do not ‘see eyes’ and ‘think’ they might be another animal any more than Tinbergen’s famous stickleback ‘thought’ red post-office vans were other male sticklebacks! (Tinbergen described how his male stickleback would respond with aggressive behaviour when the – red – post-office van drew up outside his house. Normally sticklebacks reserve this behaviour for other male sticklebacks, who have red breasts.)
This leads me on to the interesting case of the Lanternfly. In addition to the prominent pair of eyespots on the hind wings this insect has a large protuberance on the head that looks rather like a caiman or crocodile. If you suggest that this might cause a ‘startle reaction’ in predators you might well be met with a response like: ‘surely that wouldn’t fool a bird’ – or – ‘it’s far too small to be scary’. My point here is that it is just possible that predators in the same habitat as the Lanternfly might well have evolved responses to ‘caiman-like’ things. Any image fitting the ‘pattern-recognition’ template in the brain would evoke the adaptive response! (Tinbergen would call this an ‘Innate releasing mechanism’)
