Wingspan 10-16 mm.
The commonest and most widespread of the Eriocrania species that feed on birch, occurring throughout most of Britain.
The adults are difficult to tell apart from E. sangii without reference to the genitalia structure, but the larvae are quite different, semipurpurella being white or yellowish, sangii being quite dark grey.
The larva itself mines in a birch (Betula) leaf, forming a large blotch, from March to May. The adults fly in March and April, especially in sunshine.
Leafmine (British Leaf Mining Fauna)