Nationally scarce (Nb) in fens, marshes, river-banks, damp areas, golf courses, heaths and woodland edges in parts of the British Isles, less numerous in the north, predominantly coastal, a priority species under the UK Biodiversity Action Plan. In Hampshire and on the Isle of Wight mainly confined to the New Forest, with scattered records elsewhere. Wingspan male 68-84 mm, female 88-96 mm. The larvae feed internally in living wood or pith and take several years to mature. Whilst full-fed larvae are occasionally found wandering, and adults occasionally visit light, the 'easiest' way to gather evidence of this species is to find a 'Cossus tree', with multiple entrance holes indicating larval workings.