Gastropacha quercifolia, the lappet, is a moth of the family Lasiocampidae. It is found in Europe and east across the Palearctic to Japan.
The wingspan is 50–90 mm. Meyrick describes it thus - forewings with 9 to termen; red-brown, with purple-bluish gloss, towards costa blackish-mixed, dorsally ferruginous; first, second, and praesubterminal lines blackish-grey, waved, bent near costa; a blackish-grey discal mark; termen waved-dentate. Hindwings as forewings, but lines indistinct, straight, costal area ferruginous, with about six blackish pseudoneuria; 8 connected with cell by long bar. Larva dark grey or brown; whitish dorsal marks on 3 and 4; 2nd and 3rd incisions deep indigo-blue; a prominence on 1 2; a subspiracular series of tubercles and fringe of pale hairs.[1]
The larvae feed on Crataegus, Prunus spinosa, willow and oak.