Like several other Arctiidae moth larvae, the cinnabar caterpillars can turn cannibalistic. This can be due to lack of food. Sometimes they can eat other cinnabar larvae for no apparent reason. Females lay up to 300 eggs and usually in clusters of 30 to 60. The larvae start out as a pale yellow. Later larval stages develop the jet black and orange/yellow striped coloring. They can grow up to 30mm, and are voracious eaters; large populations can strip entire patches of ragwort clean, a result of their low predation.