May Highflyer Hydriomena impluviata
([Denis & Schiffermüller], 1775)
Wingspan 30-34 mm.
Quite variable across its range, the northern populations often include a number of dark grey, melanic specimens.
It is found throughout most of Britain, though is not especially common, and flies between May and July.
Alder (Alnus glutinosa) is the larval foodplant, the caterpillars spinning together the leaves during the autumn.