Sonchus milk-thistle, sow-thistle
Dichotomous table for leafminers
1a mine full depth => 2
1b mine upper- or lower-surface; larva a maggot => 4
1c galls, etc. => Tables for all parasites per species
2a narrow and long corridor; larva a maggot: Trypeta immaculata
2b mine wider or shorter, or a blotch; larva with chitinised head => 3
3a short corridor; larva with thoracic feet, lives later free in a spinning under a leaf: Agonopterix arenella
3b broad irregular corridor or elongated blotch; larva without feet, living in the mine until short before pupation: Orthochaetes setiger
4a blotch, often with an initial corridor => 5
4b corridor throughout => 9
5a blotch < 1 cm, lower-surface, usually several in a leaf; a red wart from above: Cystiphora sonchi
5b blotch > 1 cm, upper-surface => 6
6a elongated blotch (may be lobed), overlying the midrib => 7
6b blotch more rounded, not associated with the midrib => 8
7a larva solitary: Trypeta immaculata
7b larvae communal: Liriomyza bulgarica
8a frass in few small black grains: Liriomyza sonchi
8b frass in numerous strong greenish-black grains: Liriomyza endiviae
9a mine on, from or (partly) in the midrib => 10
9b mine not associated with the midrib => 14
10a secondary feeding lines conspicuous; broad, blotchy corridor with lobate branches: Trypeta immaculata
10b secondary feeding lines absent; corridor more or less pinnately branched => 11
11a branches of the mine containing strings of frass; pupation outside the mine; larva: cephalic skeleton of the Phytomyzinae-type: Liriomyza strigata
11b branches of the mine containing none or very little, grainy, frass; most frass, and the puparium, in the basis of the hollow midrib; cephalic skeleton of the Agromyzinae-type: Ophiomyia-species => 12
12a larva: rear spiraculum with 8-9 papillae: Ophiomyia cunctata
12b rear spiraculum with > 10 papillae => 13
13a larva: front spiraculum spine-like, erect: Ophiomyia pulicaria
13b front spiraculum broad, curved: Ophiomyia beckeri
14a puparium in the mine, in a, usually lower-surface, pupal chamber; corridor not unusually long: Chromatomyia cf. syngenesiae
14b unusually long gallery => 15
15a pupation external: Phytomyza marginella
15b puparium at the end of the gallery: Ophiomyia maura
Not included in the key: Cnephasia incertana; Liriomyza bryoniae, trifolii.