Onopordum, scotch thistle, cotton thistle

fam. Asteraceae

1a large and long transparant, lobed, blotch, associated with the midrib: Scrobipalpa acuminatella

1b mine not associated with the midrib, smaller, more a corridor => 2

1c galls, etc => 100

2a corridor short; larva later lives free: Agonopterix subpropinquella

2b corridor long or very long; larva remains in the mine untill close to pupation => 3

3a corridor very long; larva with chitinised head; frass in a single row; pupation outside the mine: Sphaeroderma testaceum

3b corridor not exceptionally long; frass in a double row; puparium within the mine => 4

4a corridor long, little branched, inter-parenchymal (yellow-green): Phytomyza spinaciae

4b corridor shorter, irregularly branched, not inter-parenchymal (whitish) => 5

5a corridor sides roughly parallel; larva: rear spiraculum with 6-8 papillae: Chromatomyia cf. syngenesiae

5b corridor side irregularly eaten out; rear spiraculum with 12-18 papillae: Phytomyza autumnalis

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

103 – Coleoptera

103a Apionidae: Ceratapion onopordi

103b Curculionidae: Cleonis pigra

106 – Hymenoptera

106a Cynipidae: Isocolus cirsii

107 – rust fungi

107a Pucciniaceae: Puccinia acanthii, rayssiae

108 – smut fungi

108a Microbotryaceae: Microbotryum onopordi

109 – powdery and downy mildews

109a Erysiphaceae: Golovinomyces depressus; Leveillula lappae; Podosphaera xanthii

109b Peronosporaceae: Bremia lactucae

Not included in the key: Agonopterix arenella; Coleophora onopordiella; Sphaeroderma rubidum.