An increasingly common immigrant from mainland Europe, appearing in southern England. In Hampshire and on the Isle of Wight there has been a marked increase in records, with between ten and twenty annually from 2006 to 2012, compared with less than 30 in total between 1948 and 2005, and upwards of 200 per annum in 2018. It has now established as a localised breeding species in places, particularly along the southern coast of the Isle of Wight, and is becoming increasingly frequently encountered inland.
Wingspan 28-36 mm. Most likely to be confused with second-generation Clay Triple-lines C. linearia
, but antemedian fascia usually more continuous and media fascia thicker and bolder in that species. Larva feeds on Holm Oak, but it may be using other Quercus
species in the UK.