1a fleck mine => 2

1b corridor and/or blotch => 5

1c galls, etc => Tables for all parasites per species

2a case helicoidal; hole in the mine not precisely round: Apterona gracilis

2b case tubular; hole precisely round => 3

3a composite leaf case: Coleophora onopordiella

3b tubular silken case => 4

4a case dark brown: Coleophora paripennella

4b case light brown: Coleophora peribenanderi

5a clear, long, corridor or secondary blotch => 6

5b short, relatively broad corridor, corridor-blotch or blotch => 9

6a corridor exceptionally long: Sphaeroderma rubidum

6b narrow corridor that ends upon a thick vein: Phytomyza continua

6c secondary blotch: Phytomyza lappivora

6d normal corridor => 7

7a pinnately branched corridor on top of a thick vein, side branches directed forward: Liriomyza strigata

7b corridor not associated with a vein => 8

8a pupation in the mine, in a, usually lower surface, pupal chamber: Chromatomyia cf. syngenesiae

8b pupation external; mostly many, intercrossing corridors in a leaf : Phytomyza lappae

9a clear, large, blotch => 10

9b small blotch, corridor-blotch, or mine of nondescript form => 12

10a larva a maggot; often many mines in a leaf, starting at a thick vein: Pegomya laticornis

10b larva with chitinised head => 11

11a mine contains little frass; larva mines all its life: Agonopterix carduella

11b mine with ample quantities of frass; older larvae live free among spun leaves: Tebenna micalis

12a larva without feet: Phytosciara macrotricha

12b larva with prolegs and thoracic feet => 13

13a larva: prothoracic plate brown or black, with a light anterior margin => 14

13b prothoracic plate without light anterior margin => 16

14a larva: pinacula colourless (although the base of the setae is black): Cnephasia incertana

14b pinacula black => 15

15a larva: behind/below the anus a black chitinous comb: Cnephasia asseclana

15b no anal comb present: Cnephasia stephensiana

16a head yellowish to brown; pale yellow or green: Agonopterix arenella

16b head black; green => 17

17a dull green; June – early July: Agonopterix subpropinquella

17b apple green; July – earl August: Agonopterix propinquella