1a mine large, a clear gallery or blotch; the larva mines till just before pupation => 2

1b mine small, of indefinite shape; the larva mines only briefly, then lives free among spun leaves => 4

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

2a blotch along the leaf margin; primary and secondary feeding lines conspicuous; pupation outside the mine: Agromyza dipsaci

2b corridor, not associated with the leaf margin; no feeding lines visible; pupation inside the mine => 3

3a branched corridor, not associated with midrib or leaf base, often in the leaf tip; leaf tissue around the mine turning violet: Chromatomyia succisae

3b corridors originate from the (basal part of) the midrib; no violet discolouring: Chromatomyia ramosa

4a larva: pinacula colourless (the bases of the setae themselves are black) : Cnephasia incertana

4b pinacula black: Cnephasia stephensiana