1a pinnately branched gallery, main and side branches on top of the midrib and side veins: Liriomyza strigata

1b blotch, or little, not pinnately, branched gallery; mine not determined by the leaf venation => 2

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

2a larva a maggot; mine partly or entirely upper- or lower-surface => 3

2b larva with chitinised head; mine full depth => 6

3a gallery from start to end => 4

3b blotch, may begin with a gallery => 5

4a pupation within the mine, in a, generally lower-surface, pupal chamber; frass in well-spaced grains: Chromatomyia horticola

4b pupation external; frass in strings: Liriomyza brassicae

5a frass powdery, in dark green “clouds” in corners of the mine, often visibly only after the mine has been opened: Scaptomyza flava

5b frass in black strings: Liriomyza xanthocera

6a larva with prolegs; older larvae live free at the underside of the leaf: Plutella xylostella

6b no prolegs; larvae mine all their life => 7

7a larva with thoracic legs: Phyllotreta nemorum

7b larva without legs: Ceutorhynchus minutus