1a mine less than 1 cm; the larva, with chitinised head, soon leaves the mine and continues feeding among spun leaves => 2

1b mine larger; the larva, a maggot, mines life long => 4

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

2a larva: pinacula colourless (although the basis of the setae is black): Cnephasia incertana

2b pinacula black => 3

3a larva: behind/below the anus a chitinous comb: Cnephasia asseclana

3b no anal comb present: Cnephasia stephensiana

4a pale green corridor: Phytomyza minuscula

4b large blotch, often purple brown: Phytomyza aquilegiae