Swammerdamia passerella
Dwarf Birch Drab

Wingspan c.10 mm.

A rare species, restricted in the British Isles to high altitude in the Scottish Highlands. Abroad it also occurs in the Scandinavian mountains.

The larva spins a light web on the surface of leaves of dwarf birch (Betula nana), feeding on the leaf surface within.

Adults emerge in late May, coinciding with the leaf-flush of Betula nana. They can be seen flying low over the plant in the early evening.