Polypodium, polypody

fam. Polypodiaceae

1a fleck mine: Apterona helicoidella

1b corridor or blotch => 2

1c galls, etc => 100

2a blotch, extending over several leaf segments; at the start of the mine, at the underside, an elliptic egg shell: Chirosia histricina

2b mine usually limited to one leaf segment; no egg shell visible => 3

3a frass in two rows of pearl chains (occurrence on this host very doubtful): Phytoliriomyza hilarella

3b frass in one, almost uninterrepted thread along the sides of the corridor: Chromatomyia scolopendri

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

107 – rust fungi

107a Pucciniastraceae: Milesina dieteliana

Not included in the key: Heptamelus ochroleucus.