The cinnabar moths eats away the flowers of the ragwort in high speed. What I find interesting is that the plant has poison to protect itself against being eaten. But the caterpillars eat the ragwort and use the ragwort its own poison to prevent themselves from being eaten by birds.
The not-poisonous plants near the ragwort had much less eating damage then the poisonous ragwort.
Dutch name: Sint-Jacobsvlinder