Wingspan 7-9 mm.
A common moth throughout the British Isles, this species can be found almost anywhere where the foodplant, birch (Betula) is present.
As a larva, the species forms a blotch mine on the underside of a leaf, often quite small, but puckering the leaf noticeably.
There are two generations with adults flying in May and again in August. The larvae are present in July, and more commonly in September and October.