The Cosmopolitan Leucania loreyi
Wingspan 34-44 mm.
Although it can resemble one or two related species such as The Clay (M. ferrago) and White-speck (M. unipuncta), this moth can be told apart by the pure white hindwings.
It is an immigrant to the south-west of the British Isles, with varying numbers each year, ranging from just a few to several hundred in exceptional years. The main arrival period is from August to October, though they have been recorded as early as May.
Abroad, the species occurs in southern Europe and North Africa, and is thought to feed on grasses.