Carduus thistle
Dichotomous table for leafminers
1a mine on or (partly) within the midrib => 2
1b mine not associated with the midrib => 6
1c galls, etc => Tables for all parasites per species
2a mine upper- or lower-surface; larva a maggot => 3
2b mine full depth; larva with recognisable head => 5
3a larva in the base of the swollen, galled midrib, with short extensions in the leaf: Phytomyza continua
3b midrib not galled, mine not situated so basally => 4
4a side branches slender, not very numerous; frass in strings; larva: cephalic skeleton with two backwards pointing arms: Liriomyza strigata
4b side branches short, numerous; frass in grains (most of it is invisible, deposited in the main branch); cephalic skeleton with three backwards pointing arms: Agromyza apfelbecki
5a larva without feet: Orthochaetes insignis
5b larva with prolegs and thoracic feet: Scrobipalpa acuminatella
6a mine small, of indefinite shape, sometimes many on a leaf; larva with well recognisable head => 7
6b mine not unusually small; corridor, blotch, or fleck; larva with or without a recgnisable head => 10
7a larva without feet => 8
7b larva with prolegs and thoracic feet => 9
8a the larva mines lifelong: Phytosciara macrotricha
8b older larva lives free under the leaf, causing window feeding: Phytosciara halterata
9a larva: pinacula colourless: Cnephasia incertana
9b pinacula black: Cnephasia stephensiana
10a fleck mine: larva mines from a case => 11
10b corridor or blotch; larva mines from the inside => 14
11a larva in a helicoidal case: Apterona helicoidella
11b larva in a more or less straight case => 12
12a case brownish black, lying almost flat on the leaf: Coleophora paripennella
12b case straw-coloured, not lying flat on the leaf => 13
13a mounth angle c. 50°, case c. 12 mm long: Coleophora peribenanderi
13b mounth angle 10-30°, case c. 10 mm (occurence on this hostplant uncertain): Coleophora follicularis
14a clear blotch => 15
14b corridor => 18
15a larva a maggot; near the start of the mine often an elliptic egg shell => 16
15b larva with feet and a chitinised head; no egg shell => 17
16a start of the mine (recognisable by an accumulation of frass) at the leaf margin; alpine species: Pegomya hessei
16b mines starts in tjhe centre of the leaf; lowland species: Pegomya steini
17a mine contains almost no frass: Agonopterix carduella
17b mine contains clear amounts of frass: Tebenna micalis
18a mine full depth; larva with feet and distinct head => 19
18b mine upper- or lower-surface, or inter-parenchymal; larva a maggot => 24
19a mine short; larva soon leaves and continues living free => 20
19b mine long; larva remains in the mine untill short before pupation => 22
20a head yellowish to brown; pale yellow or green: Agonopterix arenella
20b head black; green => 21
21a matt green; June – early July: Agonopterix subpropinquella
21b apple green; July – early August: Agonopterix propinquella
22a mine usually with a central, threadlike frass line: Apteropeda orbiculata
22b frass in grains, dispersed => 23
23a larva hibernates in the mine; corridor follows the leaf margin: Sphaeroderma testaceum
23b larva leaves the mine prior to hibernation; corridor less strongly associated with the leaf margin: Sphaeroderma rubidum
24a pupation in the mine => 25
24b larva leaves the mine prior to pupation => 26
25a mine long, largely inter-parenchymal, yellow-green: Phytomyza spinaciae
25b mine shorter, whitish: Chromatomyia cf. syngenesiae
26a frass in discrete grains (their distance larger than their diameter); no secondary blotch: Phytomyza cirsii
26b frass at least partly in strings; part of the corridor forms a secondary blotch: Liriomyza bryoniae
Not included in the key: Coleophora trochilella; Jordanita notata; Pegomya terebrans; Phytomyza cirsiophaga (insufficiently known); Scrobipalpa perinii.