Dave Cheetham (July)
These distinctive yellow and black caterpillars were munching away on some ragwort at South Stacks on Anglesey. They are Cinnabar Moth caterpillars.
The Cinnabar moth is a brightly coloured red and black moth which is named after the red mineral cinnabar because of the red patches on its predominantly black wings. It has been documented as the most poisonous species of moth in britain.
The caterpillars are immune to the strong poisons contained in ragwort, their common foodplant, and actually assimilate the toxins, becoming poisonous themselves. The bright colour of both caterpillar and moth acts as an effective warning sign to predators rather than camouflage.
Cinnabar caterpillars can become cannabalistic. Apparently although this is often due to lack of food, they can eat other Cinnabar caterpillars for no apparent reason.
Cinnabar Caterpillars are voracious eaters and can strip entire patches of ragwort clean, this is due to them reproducing in great number, often hundreds in a very small area, also a result of their low predation.
In Australia they have been actively introduced to control the spread of ragwort.