Warning colouration
Along with the colour and behaviour often goes the foul smell of their chemical weapons. Noxious caterpillars often have thick, leathery cuticles which help them to resist young birds making a 'test'. When the bird takes a peck, disgusting fluid seeps out from special glands on its back. Kegan Paul, London. All in all, the predator is given good warning. Tests show that warning colours definitely do deter predators.