1a mine exclusively in the leaf blade => 2

1b next to the blade also the petiole is mined out => 5

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

2a fleck mine: Apterona elicoidella

2b corridor or blotch => 3

3a frass in strings; branched corridor: Liriomyza strigata

3b frass in fine grains; whitish blotch => 4

4a on Viola palustris: Galiomyza beckeri

4b on V. reichebachiana, riviniana, tricolor: Galiomyza violiphaga

5a larva a maggot: Liriomyza violicaulis

5b larva with feet and chitinised head: Pancalia nodosella