1a leaf tip rolled in: Chirosia betuleti

1b mine lower in the leaf, leaf remains flat => 2

1c galls, etc => Tables for all parasites per species

2a mine in midrib and/or petiole (occurence on this hostplant uncertain): Heptamelus ochroleucus

2b blotch mine in the leaf disk => 3

3a larva with recognisable head and feet, normally not a miner: Psychoides filicivora

3b larva a maggot, obligate miner: Chirosia histricina