Swammerdamia passerella
Swammerdamia passerella
Larva • Larva in web on Betula nana in blanket bog (at around 200m a.s.l) The Crask, Sutherland. August. • © Duncan Williams

16.016 BF437a

Swammerdamia passerella

(Zetterstedt, 1839)

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.
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