1a mine full depth; larva with thoracic feet and a sclerotised head =>2

1b mine upper- or lower-surface; larva a maggot => 3

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

2a alpine species; pinacula black: Cnephasia sedana

2b lowland species; pinacula colourless (only the base of the setae black): Cnephasia incertana

3a first part of the mine a long, very narrow corridor; in the later part of the mine primary and secondary feeding lines are conspicuous => 4

3b mine different; no conspicuous feeding lines => 6

4a the first, corridor-part of the mine girdles a part of the leaf, that turns brown and withers; here a large blotch is made: Stemonocera cornuta

4b no girdling => 5

5a the latter part of the mine is a broad gallery, centered over the midrib: Trypeta zoe

5b the latter part is a broad secondary blotch without association with venation: Acidia cognata

6a pupation within the mine; the front spiracula of the puparium penetrate the epidermis => 7

6b pupation outside the mine; the larva leaves the mine by a semicircular slit in the epidermis => 8

7a corridor whitish (when illuminated from above), not conspicuously long; frass in dispersed grains: Chromatomyia cf. syngenesiae

7b corridor yellowish, up to 20 cm long; frass in long pearl chains: Phytomyza farfarae

8a corridor entirely upper-surface: Phytomyza tussilaginis

8b first part of the corridor lower-surface, often stellate: Phytomyza adenostylis