You may have noticed ragwort in flower when out and about recently.
Whilst it is poisonous to horses (should they accidentally eat it), especially if cut and dried and fed in hay, ragwort is of great importance to the cinnabar moth.
Cinnabar is a red mercury sulphide and due to the red on the adult moths wing, this is how it got its name.
The female cinnabar moth lays up to 300 eggs in batches of 30 or 40 on the underside of ragwort leaves. The caterpillars feed on ragwort leaves and flowers from July to September. Just a few caterpillars can quickly reduce a ragwort plant to a bare stem. Ragwort contains a poison, this poison is stored in the caterpillars and moths body. The caterpillars have bright yellow and black stripes to deter predators. Any birds or other predators who ignore the caterpillars warning colours will be repulsed by how foul they taste. The adults’ bright red and black also deters any would be predators.
When fully fed, the caterpillars crawl away from the ragwort stem to pupate in a dry sheltered spot such as among the debris at the base of the plants or into crevices under logs, stones and lumps of earth. This means there needs to be enough ragwort for them to feed on to get big enough to pupate. The pupa is dark brown and is sometimes enclosed in a loosely spun silken cocoon.
The pupal stage lasts about nine months, with the moths emerging the following spring to start the cycle of life again.
The number of cinnabar moths has dropped dramatically due to the persecution of their food plant – ragwort.
Recently we have had a number of ragwort raids on a number of our sites between Tintagel and Holywell. Our aim is not to remove all the plants as this would mean loosing the beautiful cinnabar moth. Our aim is to manage the spread of the plant so it doesn’t completely take over and reduce a sites biodiversity. Our priority areas are near horse grazing paddocks and hay meadows. We have removed thousands of ragwort plants which will now need to be burnt as we can’t compost it or send it to landfill.
When you see us out and about pulling up ragwort (we need to remove the roots or it will just re-grow next year), you may see us leave a few – that’s because they have cinnabar moth caterpillars on. We hope we have left them enough ragwort so that they can fatten up and pupate successfully. But we also hope that we are helping to reduce the spread of the plant. Its all about balance and diversity.
Sarah Stevens, Ranger, Tintagel to Holywell