1a mine < 1 cm, often in numbers together in a leaf axil; larvae, with distinct feet, later live free and cause extensive window feeding => 2

1b mine > 1 cm; larva without feet => 3

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

2a larva: head pale brown: Epermenia chaerophyllella

2b head black: Epermenia aequidentellus

2c larva not described: Epermenia iniquellus

3a long, narrow corridor, abruptly widened into a primary blotch; larva with chitinised head: Fomoria viridissimella

3b mine different, larva a maggot => 4

4a primary blotch mine => 5

4b corridor or secondary blotch mine => 7

5a secondary feeding lines conspicuous (common species): Euleia heraclei

5b secondaire feeding lines weak or absent (species not known from the Benelux) => 6

6a frass grains coarse; on different Peucedanum species: Phytomyza pauliloewii

6b frass grains not remarkable; on Peucedanum cervaria: Phytomyza peucedani

7a puparium in the mjne: Chromatomyia horticola

7b larva leaves the mine prior to pupation => 8

8a frass in the oldest section of the gallery in small grains: Phytomyza thysselini

8b frass here in pearl chains: Phytomyza thysselinivora