1a mine either begins or ends in stem, petiole or midrib => 2

1b mine at most on the midrib, otherwise free in the leaf => 4

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

2a larva with chitinised head; mine begins on a galled and swollen part of stem or petiole => 3

2b larva a maggot; petiole normal: Scaptomyza flava

3a galled swelling of the stem conspicuous, containing ca. 3 larvae: Ceutorhynchus napi

3b galled swelling weak, usually containing 1 larva: Ceutorhynchus rapae

4a mine full depth; larva with chitinised head: Ceutorhynchus minutus

4b mine upper- or lower-surface (small patches sometimes full depth); larva a maggot => 5

5a corridor from start to end => 6

5b irregular blotch, preceded by a narrow corridor (may be overrun): Scaptomyza flava

6a broad corridor upon the midrib, pinnately branched: Liriomyza strigata

6b corridor little branched, not pinnate, not associated with the midrib => 7

7a puparium in the mine in a, usually lower-surface, pupal chamber; frass in discrete grains: Chromatomyia horticola

7b larva leaves the mine before pupation through a semicicular exit slit; frass in thread fragments => 8

8a larva: rear spiraculum with 3 papillae: Liriomyza brassicae

8b rear spiraculum with 7-12 papillae: Liriomyza bryoniae