1a fleck mine: small, full depth blotch without frass, with a relatively opening by which the larvae has accessed the leaf tissue => 2

1b no fleck mine, but a corridor or blotch with clear amounts of frass => 4

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

2a larva mines from a helicoidal case => 3

2b larva does not mine from a case: Aricia agestis

3a suture between the windings of the case very shallow: Apterona gracilis

3b suture normal, deep: Apterona helicoidella

4a the oviposition spot, where the mine begins, covered by a drop of dried secretion: Habroloma triangulare

4b no such drop => 5

5a mine small; larva with legs and chitinised head; the older larva lives free among spun leaves: Cnephasia incertana

5b mine not remarkably small; the larva, a maggot, mines all its life => 6

6a species of the Canary Islands: Agromyza erodii

6b species of continental Europe: Agromyza nigrescens