1a mine full depth; larva with chitinised head => 2

1b mine upper- or lower-surface (sometimes full depth in places); larva a maggot => 4

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

2a small blotch, < 1 cm; older larvae live free: Plutella xylostella

2b mine > 1 cm, corridor or blotch; larvae remains in the mine till pupation => 3

3a larva without feet; mine an untidy corridor: Ceutorhynchus minutus

3b larva with thoracic feet; a corridor, ending blotchy: Phyllotreta nemorum

4a corridor from start to end => 5

4b irregular blotch, prededed by a narrow corridor (may be overrun later) => 6

5a broad, pinnately branched corridor, main branch overlying the midrib; frass in strings: Liriomyza strigata

5b corridor little branched, not pinnate, not associated with the midrib; frass in discrete grains: Chromatomyia horticola

6a frass in thread fragments; mine in May-June: Liriomyza xanthocera

6b frass powdery, in blackish-green clouds; mine in May-October: Scaptomyza flava