Prenanthes purple lettuce
Dichotomous table for leafminers
1a primary blotch => 2
1b more or less broad corridor => 3
1c galls, etc => Tables for all parasites per species
2a larva solitary; rear spiraculum with 3 papillae: Liriomyza puella
2b larvae often communal; rear spiraculum with 8 papillae: Liriomyza sonchi
3a long corridor, party lower-, partly upper-surface, almost independent of the leaf venation: Phytomyza marginella
3b corridor not remarkably long, following the leaf venation, of originating from a vein => 4
4a several short corridors, originating independently from the midrib: Ophiomyia pulicaria
4b corridor overlying the midrib and lateral veins => 5
5a corridor broad; primary and secondary feeding lines conspicuous; frass in angular grains: Trypeta immaculata
5b corridor narrow; only secondary feeding lines visible; frass in strings: Liriomyza strigata
Not included in the key: Liromyza hieracii; Ophiomyia cunctata.