Species account from Moths of Glamorgan
(Gilmore, Slade & Stewart, 2009):

Univoltine, flying from May until August in most habitats but most numerous on grassland and sand dunes. Flies by day, sometimes in abundance but comes sparingly to light. The yellow and black striped caterpillars are often conspicuous on ragwort, though when this is exhausted they have been recorded on other species including Colt’s-foot.