1a larva in the midrib near the leaf apex that curls downwards: not a true miner: Chirosia grossicauda

1b corridor or blotch mine => 2

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

2a larva with feet and chitinised head => 3

2b larva a maggot => 4

3a larva: head and pronotum brown-black: Psychoides verhuella

3b head and pronotum very pale brown: Psychoides filicivora

4a on Asplenium ceterach: Chromatomyia dorsata

4b on other species: => 5

5a blotch mine that occupies several pinnulae: Chirosia histricina

5bcorridor or a secondary blotch that occupies a single pinnula => 6

6a corridor ≤ 4 cm; frass in two rows of pearl chains (occurrence on this host plant doubtful): Phytoliriomyza hilarella

6b corridor often longer; frass in a long line along one of the sides: Chromatomyia scolopendri