1a fleck mine; larva mines from a helicoidal case: Apterona paludella

1b no fleck mine; larva mines from the inside => 2

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

2a mine small, full depth, of indefinite shape; in most species the older larvae live free=> 3

2b mine not uncommonly small, an upper- or lower-surface corridor; larvae mine all their life => 7

3a larvae with thoracic feet => 4

3b no thoracic feet => 6

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

4b pinacula black => 5

5a larva: behind/below the anus a chitinous comb: Cnephasia asseclana

5b anal comb absent: Cnephasia stephensiana

6a older larvae live free, causing window feeding: Phytosciara halterata

6b larvae mine all their life: Phytosciara macrotricha

7a corridor from start to end => 8

7b widening corridor, turning into a blotch along the leaf margin => 9

8a corridors radiating from the petiole into the leaf blade: Phytomyza soenderupi

8b corridors not radiating from the petiole: Phytomyza calthophila

9a initial corridor following the leaf margin, with smooth sides and little or no frass grains: Phytomyza calthae

9b initial corridor winding from the leaf basis towards the leaf margin; sides irregularly eaten out; frass in pearl chains: Phytomyza calthivora