Eryngium, sea holly, field eryngo

fam. Apiaceae

1a larva with thoracic feet and chitinised head; mine for a large part in the rind of the stem => 2

1b larva a maggot; mine intirely in the leaf => 3

1c galls, etc => 100

2a larva with prolegs: Stomopteryx detersella

2b no prolegs; only on E. campestre: Dibolia timida

3a blotch mine, may be preceded by a short broad corridor; feeding lines conspicuous: Euleia heraclei**

3b corridor mine => 4

4a puparium in the mine, usually in an lower-surface pupal chamber; frass in isolated grains: Chromatomyia horticola

4b puparium formed after the mine has been vacated; frass in strings or absent => 5

5a corridor short, not strongly branched, almost without frass: Euleia heraclei**

5b corridor pinnately branched or branches fanning out from the leaf basis: Liriomyza strigata

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

102 – Acari

102a Eriophyidae: Aceria eryngii

104 – Diptera

104a Cecidomyiidae: ? Dasineura kiefferi; Lasioptera ? carophila, eryngii

107 – rust fungi

107a Pucciniaceae: Aecidium virgatum; Puccinia eryngii, isiacae

109 – powdery and downy mildews

109a Erysiphaceae: Leveillula braunii, lanuginosa

109b Erysiphaceae: Erysiphe heraclei

** Eryngium is an unsuitable hostplant for Euleia heraclei and most larvae die early, before they have formed a blotch.

Not included in the key: Dibolia cryptocephala; Tebenna micalis.