Comarum marsh cinquefoil, swamp cinquefoil
Comarum has recently (once again) been split off Potentilla; please try that key as well.
Dichotomous table for leafminers
1a blotch mine => 2
1b gallery nine, starting at a semi-globular shining egg shell: Stigmella poterii
1c fleck mine; larva in a transportable case: Coleophora albicostella
1d galls, etc => Tables for all parasites per species
2a larva a maggot: Agromyza idaeiana
2b larva with differentiated head, and thoracic feet: Fenella nigrita