1a mine < 1 cm long, full depth; the larvae, with thoracic feet and chitinised head, soon leave the mine and continue to live free => 2

1b mine longer, upper- and/or lower-surface; the larva, a maggot, mines all its life => 5

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

2a mine more or less a corridor, usually several in a nerve axil; larva pale (whitish to light green): Epermenia chaerophyllella

2b mine more of a blotch, never numerous in a leaf axil; larva green to blackish => 3

3a mine contains an appreciable amount of frass; older larva in a rolled leaf: Agonopterix purpurea

3b mine contains little or no frass; older larvae among spun leaves => 4

4a larva: pinacula black: Cnephasia asseclana

4b pinacula colourless (but the base of the setae black): Cnephasia incertana

5a the mine begins with a long lower-surface section, then upper-surface: Phytomyza biseta

5b mine upper-surface from begin to end => 6

6a very common, broadly oligophagous species, occurring in almost entire Europe: Phytomyza chaerophylli

6b Central European species, known from Chaerophyllum temulum: Phytomyza chaerophylliana

6c Central European species, known from Chaerophyllum aromaticum, aureum, hirsutum: Phytomyza aurei