1a corridors, radiating from the leaf base or the midrib => 2

1b mine different => 4

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

2a the mine begins at a gall in the petiole: Ceutorhynchus chalibaeus

2b no gall in the petiole => 3

3a side branches originate from the midrib: Ceutorhynchus erysimi

3b side branches originate from a main branch that lies on top of the midrib: Liriomyza strigata

4a larva with recognisable head => 5

4b larva a maggot => 8

5a larva with thoracic feet => 6

5b larva witout feet: Ceutorhynchus minutus

6a larva with prolegs => 7

6b no prolegs: Phyllotreta nemorum

7a older larvae live free under the leaf, causing window feeding: Plutella xylostella

7b older larvae live among spun leaves: Cnephasia incertana

8a frass powdery, in dark green clouds in remote corners of the mine: Scaptomyza flava

8b frass in black grains or strings => 9

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

9b pupation external => 10

10a corridor from start to end (although here and there branches may coalesce into a secondary blotch): Liriomyza bryoniae

10b mine begins as a corridor but widens, usually on top of the midrib, into an irregular primary blotch: Liriomyza xanthocera