Very rare immigrant from mainland Europe, appearing in southern England. Not recorded in Hampshire or on the Isle of Wight to date. Wingspan male 36-39 mm, female 40-46 mm. Similar to
Oak Processionary T. processionea, which see for differences. Distinguished from
Pale Eggar Trichiura crataegi by the comma-shaped marking in the centre of the forewing. Larva feeds on Corsican Pine and Maritime Pine, living gregariously within a silken web. The caterpillars release urticating hairs, which may cause severe irritation of the skin and mucous membranes.