fam. Asteraceae

1a larva with thoracic feet and a chitinised head => 2

1b larva a maggot => 4

1c galls, etc => 100

2a mine a large corridor; larva mines all its life: Digitivalva arnicella

2b mine tiny, irregular; older larvae live free among spun leaves => 3

3a larva with black pinacula: Cnephasia stephensiana

3b pinacula colourless: Cnephasia incertana

4a corridor, widening into a large blotch: Phytomyza arnicae

4b corridor from begin to end => 5

5a pupation within the mine, in a, usually lowr-surface, pupal chamber: Chromatomyia cf. syngenesiae

5b pupation outside the mine => 6

6a frass in small grains, close together, or in pearl chains: Phytomyza conyzae

6b frass in large, widely separated grains: Phytomyza arnicicola

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 Tephritidae: Tephritis arnicae

106 – Hymenoptera

106a Cynipidae: Aulacidea arnicae

108 – smut fungi

108a Entylomataceae: Entyloma arnicale

109 – powdery and downy mildews

109a Erysiphaceae: Podosphaera senecionis, xanthii

Not included in the key: Coleophora paripennella.