1a mine < 1 cm, full depth, often in numbers together in a leaf axil; larvae, with distinct feet and chitinised head, later live free and cause extensive window feeding: Epermenia chaerophyllella

1b mine > 1 cm, not full depth; larva a maggot => 2

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

2a primary blotch: Euleia heraclei

2b corridor, rarely locally a secondary blotch: Phytomyza spondylii + Ph. pastinacae