Prenanthes, purple lettuce

fam. Asteraceae

1a primairy blotch => 2

1b more or less broad corridor => 3

1c galls, etc => 100

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 idependently 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

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: Mycodiplosis coniophaga

104b Tephritidae: Ensina sonchi

105 – Hemiptera

105a Triozidae: Trioza foersteri

107 – rust fungi

107a Pucciniaceae: Puccinia maculosa

109 – powdery and downy mildews

109a Erysiphaceae: Golovinomyces prenanthis; Podosphaera xanthii

110 – other causers

110a Fungi, Protomycetaceae: Protomyces kreuthensis

Not included in the key: Liromyza hieracii; Ophiomyia cunctata.