The larvae absorb toxic and bitter tasting alkaloid substances from the food plants, and assimilate them, becoming unpalatable themselves.

[2] The bright colours of both the larvae and the moths act as warning signs, so they are seldom eaten by predators.

An exception is among different species of cuckoo which eat hairy and poisonous caterpillars including cinnabar moth larvae.

They can grow up to 30 mm (1.2 in), and are voracious eaters; large populations can strip entire patches of ragwort clean, a result of their low predation.

Often, very few survive to the pupal stage, mainly due to them completely consuming the food source before reaching maturity; this could be a possible explanation for their tendency to engage in seemingly random cannibalistic behaviour, as many will die from starvation.