1a larvae with thoracic feet and recognisable head; older larvae live free, in a web => 2

1b larvae without feet, no recognisable head; they mine until just before pupation => 3

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

2a several small galleries in a leaf: Yponomeuta sedella

2b a single blotch: Cnephasia sedana

3a larva: both rear spiracula fused into a strongly chitinised respiratory tube => 4

3b rear spiracula free from each other => 5

4a respiratory tube with 5 + 5 openings: Cheilosia rhodiolae

4b respiratory tube with 3 + 3 openings: Cheilosia semifasciata (occurrence on this hostplant improbable)

5a rear spiracula of larva and pupa strikingly forked: Phytomyza rhodiolae

5b rear spiracula not strongly bifid: Phytomyza sedicola