Wingspan c. 11-15mm.
A rare species in the British Isles, known from submontane habitats and glens, until recently known only from a handful of locations in northern Scotland.
In 2006 it was discovered at Whixall Moss in Shropshire, and more recently just over the border from Fenn's moss in Denbighshire. These findings constitute the first records for both England and Wales.
The adult moths, on the wing in June, are quite distinctive, with a strongly falcate or hooked outer forewing, and a brownish ground colour with a greyish white blotch in the ocellar region.
The larvae feed on birch (Betula), spinning leaves together.