The caterpillar of the cinnabar moth is one of the few that I can identify instantly. It is also a caterpillar that birds quickly learn to recognise; for the very good reason that it has an unpleasant taste. Once a bird has tasted a cinnabar caterpillar, it learns to leave them alone. The bold black and yellow stripes are a warning of retribution as bold as those of a wasp. Cinnabar caterpillars feed on the leaves of ragwort and sometimes groundsel and coltsfoot. They live in groups that hatch from one batch of eggs and strip the host plant of its leaves. They then migrate to another plant. Or they die, as these caterpillars did, because there was no other suitable food plant within range of this solitary ragwort. If they survive and pupate, they eventually emerge as black and red adult moths. They are as conspicuous and as poisonous as the caterpillars. The source of the poison is the ragwort, which produces alkaloids in its leaves. Ragwort is poisonous to horses but not to sheep – and not to cinnabar caterpillars which store the poisons in their bodies. It may seem a bit pointless for an insect to be distasteful if a bird only discovers the fact after it has eaten it. The idea is that the bird will reject any other insect showing the same colours. So the insect has paid the ultimate sacrifice to save its "cousins, sisters and aunts". And it will have been unlucky that it was found by a naïve bird that had never met any other similarly inedible insect sporting the same colours: other cinnabars, wasps, burnet moths or ladybirds.
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