1a mine transparant, full depth, usually a blotch; larva with chitinised head => 2

1b mine upper- or lower-surface, greenish in transparency, more or less a corridor; larva a maggot => 3

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

2a at the point of oviposition a shining black drop of dried secretion; pupation within the mine: Trachys subglaber , possibly also T. troglodytes

2b no such black drop; larva mines from a silken tube: Scythris picaepennis

3a mine not associated with the midrib => 4

3b mine radiation from, or positioned over, the midrib => 6

4a frass almost absent, or a few big lumps at the end of the mine; puparium formed after the mine has been vacated; often a secondary blotch: Aulagromyza similis

4b frass present, grains, strings etc; puparium formed within the mine => 5

5a corridor long, in the distal half of the leaf; turning the surrounding leaf tissue violet: Chromatomyia succisae

5b corridor shorter; no preferred position; no discolouring of the leaf: Chromatomyia horticola

6a corridors in the leaf blade radiate from the basal half of the midrib: Chromatomyia ramosa

6b corridor pinnately branched, its main axis overlying the midrib: Liriomyza strigata