1a larva in stem and petioles, sometimes making excursions into the leaf that start from the midrib => 2

1b larva not in stem or petiole => 3

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

2a the larva induces a gall; larva without feet: Ceutorhynchus pectoralis

2b no gall; larva with thoracic feet: Psylliodes napi

3a mine full depth; larva with chitinised head => 4

3b mine upper- and/or lower-surface; larva a maggot => 7

4a mine small, < 1 cm; frass in discrete grains; larva, with abdominal and thoracic feet, later lives free: Plutella xylostella

4b mine > 1 cm, a corridor or blotch; frass in lumps or strings; larva without abdominal feet => 6

5a older larvae live among spun leaves: Cnephasia incertana

5b older larvae live at the underside of the leaf: Plutella xylostella

6a frass partly in strings; mine an untidy corridor; larva without thoracic feet: Ceutorhynchus minutus

6b frass in lumps; mine more blotchy; larva with thoracic feet: Phyllotreta nemorum

7a upper- and/or lower-surface blotch, preceded by a narrow corridor (may have been overrun later); frass powdery, in blackish-green clouds: Scaptomyza flava

7b corridor mine; frass black, coarser => 8

8a pinnately branched corridor, main branch overlying the midrib: Liriomyza strigata

8b corridor litle branched, not pinnate, not associated with the midrib => 9

9a pupation within the mine, in a, usually lower-surface, pupal chamber; frass in discrete grains: Chromatomyia horticola

9b pupation external; frass in long strings: Liriomyza brassicae