1a mine large; larva, white or pale, mines till just before pupation => 2

1b mine small; larva, darkly coloured, mines only briefly, lives later free among spun leaves => 3

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

2a upper of lower-surface corridor; frass in strings; larva a maggot: Phytomyza digitalis

2b full depth corridor or blotch; frass absent or in irregular grains; larva with chitinised head: Apteropeda orbiculata

3a larva: pinacula colourless (the bases of the setae themselves are black) : Cnephasia incertana

3b pinacula black: Cnephasia asseclana