1a fleck mine; larva mines from a case => 2

1b corridor or blotch mine; larva mines from the inside => 3

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

2a case squat, hoary, greyish; mines only along the leaf margin: Coleophora pennella

2b case slender, almost bare, brown black; mines scattered over the leaf disk: Coleophora pulmonariella

3a larva with chitinised head; final mine at least partly full depth => 4

3b larva a maggot; mine never and nowhere full depth => 9

4a mines small, usually a large number in a leaf; larva without feet: Phytosciara macrotricha

4b mines usually single; larva with thoracic feet => 5

5a mines quite small; older larvae life free among spun leaves => 6

5b mines of normal size; larvae mine all their life => 7

6a pinacula colourless (but the bases of the setae themselves are black): Cnephasia incertana

6b pinacula black: C. stephensiana

7a blotch, preceded by a long narrow corridor => 8

7b blotch without a preceding corridor: Dialectica imperialella

8a pupa naked in the mine, upon pupation working itself halfway out: Dialectica scalariella

8b pupa in a cocoon, remains within the mine: Perittia echiella

9a long corridor; frass in discrete grains; puparium within the mine, in a, generally lower-surface, pupal chamber; the front spiracula of the puparium penetrate the epidermis: Chromatomyia horticola

9bmine different => 10

10a larva: cephalic skeleton with 3 backwards pointing arms; mine probably in all cases a primary blotch with a long initial corridor (may have been overrun by the blotch) => 11

10b cephalic skeleton with 3 backwards pointing arms; mine probably in all cases a blotch without a preceding corridor => 12 [this section of the key is based on Beiger (1975a)]

11a larva: mandible with 2 teeth, that alternate (seen from the side therefore virtually 4 teeth); mine communal, its first section already 5-10 mm wide: Agromyza ferruginosa

11b mandible with 2 teeth, not alternating; mine solitary, beginning with narrow preceding corridor (later the corridor may become overrun; moreover, mostly several blotches on a leaf fuse into one large and communal final mine): Agromyza abiens

11c the larvae of Agromyza myosotidis are unknown; species unknown from the Benelux (but that doesn’t mean much); probably they live solitary in not-coalescing blotches.

12a lavae communally => 13

12b larva solitary => 14

13a larva: front spiraculum with 17-19, rear spiraculum with 23-25 papillae: Phytomyza medicaginis

13b front spiraculum with 13-15, rear spiraculum with 19-21 papillae: Phytomyza nowakowskiana

14a larva: front spiraculum with 15-18, rear spiraculum with 18-19 papillae: Phytomyza myosotica [occurrence on Symphytum doubtfull]

14b front spiraculum with at most 10 papillae => 15

15a larva with big hump on the mesothorax: Phytomyza pulmonariae

15b no such hump => 16

16a mainly on Lithospermum: Phytomyza lithospermi [occurrence on Symphytum not quite certain]

16b on Symphytum ottomanum: Phytomyza rhodopaea [position in the key uncertain]