1a the larve mines several leaves, migrating from one leaf to the other by boring through the stem: Delia echinata

1b the larve is limited to a single leaf, never bores in the stem => 2

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

2a corridor from start to end, pinnately branched: Liriomyza strigata

2b in the end a blotch = 3

3a frass as fine black granules: Amauromyza flavifrons

3b frass powdery, in green “clouds” in corners of the mine (it is advisable to open the mine): Scaptomyza graminum