1a larva a maggot; mine partly or entirely upper- or lower-surface =>2

1b larva with chitinised head; mine full depth => 3

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

2a frass powdery, in dark green “clouds” in corners of the mine, often visibly only after the mine has been opened: Scaptomyza flava

2b frass in black strings: Liriomyza xanthocera

3a larva with prolegs; older larvae live free => 4

3b no prolegs; larvae mine all their life => 5

4a larva light coloured; older larvae live under the leaf: Plutella xylostella

4b larva dark coloured; older larvae between spun leaves: Cnephasia incertana

5a larva with thoracic legs: Phyllotreta nemorum

5b larva without legs: Ceutorhynchus minutus