There are so many of these Tyria jacobaeae around the allotment site at the moment. For the last few visits someone asks "what are these?" and I've known immediately that the answer is "cinnabar moth caterpillar" even before seeing what they're pointing at!
Wherever there is a tuft of groundsel or ragwort there will be at least one caterpillar.
Unfortunately we'll have to wait till next year before we again see the striking red and black moths. The caterpillars pupate over Winter, under the ground, and will emerge in late Spring. We often find the red/brown chrysalis and re-bury them. Cinnabar moths and their caterpillars only have a taste for the poisonous ragwort and groundsel so aren't a problem on the plot.