1a large, untidy fleck mine; the opening is a lateral slit: Jordanita subsolana

1b blotch or gallery => 2

1c galls, etc => 100

2a gallery; larva a maggot => 3

2b blotch; larva with well visible head and feet => 4

3a frass in dicrete grains; puparium in the mine, in a, usually lower-surface, pupal chamber: Chromatomyia cf. syngenesiae

3b frass in long threads; pupation after the mine has been vacated: Phytomyza bipunctata

4a elongate blotch overlying the midrib; larva mines all its life: Gnorimoschema ochraceellum

4b mine not associated with the midrib; older larvae live free => 5

5a mine contains much frass: Tebenna micalis.

5b little frass: Agonopterix ferocella

100a Nematoda => 101

100b Acari => 102

100c Coleoptera => 103

100e Diptera => 104

100f Hemiptera => 105

100d Hymenoptera => 106

100g rust fungi => 107

100h smut fungi => 108

100i powdery and downy mildews => 109

100j other causers => 110

104 – Diptera

104a Cecidomyiidae: Urophora pontica

107 – rust fungi

107a Pucciniaceae: Puccinia echinopis, pulvinata

109 – powdery and downy mildews

109a Erysiphaceae: Golovinomyces echinopis; Leveillula lappae, picridis

109b Peronosporaceae: Bremia lactucae