Sonchus, milk-thistle, sow-thistle

fam. Asteraceae

1a mine full depth => 2

1b mine upper- or lower-surface; larva a maggot => 4

1c galls, etc. => 100

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 thorughout => 9

5a blotch < 1 cm, lower-surface, usally 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 puparium outside the mine; mine begins with an unusually long lower-surface corridor: Phytomyza marginella

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

101 – Nematoda

101a Anguinidae: Ditylenchus dipsaci

102 – Acari

102a Eriophyidae: Aceria sonchi

105 – Hemiptera

105a Aphididae: Hyperomyzus lactucae, pallidus

106 – Hymenoptera

106a Cynipidae: Aulacidea follioti; Timaspis sonchi

107 – rust fungi

107a Coleosporiaceae: Coleosporium sonchi

107b Pucciniaceae: Miyagia pseudosphaeria; Puccinia littoralis, opizii, isiacae, sonchina

108 – smut fungi

108a Entylomataceae: Entyloma crepidicola, sonchi

109 – powdery and downy mildews

109a Erysiphaceae: Golovinomyces sonchicola; Neoërysiphe nevoi; Podosphaera senecionis, xanthii

109b Peronosporaceae: Bremia stellata

110 – other causers

110a Fungi, Albuginaceae: Pustula obtusata

110b Fungi, Protomycetaceae: Protomyces sonchi

110c Fungi, Synchytriaceae: Synchytrium globosum

Not included in the key: Cnephasia incertana; Liriomyza bryoniae, trifolii.