1a larva mines from a transportable case, makes fleck mines => 2

1b larva mines from the inside; no fleck mines => 3

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

2a case helicoidal; opening in the mine relatively large, irregular: Apterone helicolidella

2b case more or less straigt; opening small, perfectly circular: Coleophora onopordiella

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

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

4a small blotch, < 1 cm; frass, as far as present, in discrete grains; larva, with abdominal and thoracic feet, later lives free => 5

4b mine > 1 cm, frass sticky, larva without abdominal feet => 6

5a larva light coloured; older larvae live at the underside of the leaf: Plutella xylostella

5b larva dark; older larvae among spun leaves: Cnephasia incertana

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

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

7a eventually a blotch mine => 8

7b corridor from start to end => 9

8a frass powdery, in blackish-green clouds; mine in May-October: Scaptomyza flava

8b frass in thread fragments, black; mine in May-June: Liriomyza xanthocera

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

9b pupation after the mine has been vacated; frass in pearl chains or strings => 10

10a pinnately branched corridor, main branch overlying the midrib: Liriomyza strigata

10b corridor little branched, not pinnate, not associated with the midrib: Liriomyza brassicae