See updated information on the Cinnabar Moth and caterpillar. The bright colours of both The Cinnabar caterpillar and the red and black adult moth are thought to be a warning to predators that they are distasteful. The caterpillars are most often found on Common Ragwort (Senecio jacobaea) which is poisonous to some animals such as horses and in some countries the caterpillars have been introduced to control the plant. The caterpillars obtain a bitter alkaloid taste from their food plant making them too distasteful for predators such as birds to eat.
For other caterpillars see British moth caterpillars gallery