Ragwort is poisonous and quite a nasty plant, brush against it and it might give you a rash. It can kill horses, but they do normally avoid it. This caterpillar of the Cinnabar Moth, though is quite happy to eat the plant. It absorbs the poisons, and this prevents birds from trying to eat it.
Photo taken in the summer, been a bit too busy to get out and about at the moment.
