1a larva with thoracic feet and a chitinised head => 2

1b larva a maggot without feet or recognisable head => 8

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

2a the larva bores in the stem, but sometimes makes short excursions into the blade => 3

2b the mine begins in the blade => 4

3a the oviposition site, just above a node in the stem, is covered with a dried drop of secretion: Cylindromorphus gallicus

3b no such drop: Glyphipterix fuscoviridella

4a the mine extends into a bore tunnel in the ste => 5

4b the larve lives entirely as a leafminer => 6

5a mine a gallery from the leaf-tip to its base: Photedes morrisii

5b mine undescribed: Ochsenheimeria vaccuella

6a larva: has ventrally on each segment a light spot: Cosmopterix orichalcea

6b no such series of spots => 7

7a a large number of Elachistidae species occur on Festuca. Their mines are hardly diagnostic and the larvae of many are badly known. A key cannot be constructed: Elachista adscitella, albifrontella, apicipunctella, argentella, baltica, bedellella, bifasciella, bisulcella, bruuni, canapennella, collitella, dispilella, dispunctella, distigmatella, festucicolella, freyerella, griseella, herrichii, humilis, irenae, luticomella, maculicerusella, nitidulella, nobilella, obliquella, occulta, pollinariella, pullicomella, rufocinerea, spumella, stabilella, subnigrella, szocsi, triatomea, triseriatella, utonella

8a larva: mandible with 1 tooth; at the start of the mine (often within a leaf sheath) at the outside an egg shell: Hydrellia griseola

8b mandible with 2 or more teeth; no egg shell visible => 9

9a larva: cephalic skeleton of Agromyzinae-type; pupation outside the mine => 10 *

9b cephalic skeleton of Phytomyzinae-type; pupation within or outside the mine => 11

10a larva: mandible with 4 teeth: Agromya albipennis

10b mandible with 3 teeth (the basal one clearly smaller than the other two): Agromyza mobilis & A. nigrella

11a puparium in the mine => 12

11b pupation outside the mine => 19

12a puparium: either front or rear spiraculum penetrate the epidermis => 13

12b puparium not connected with the outside world => 16

13a larva and puparium with rear spiracula strongly enlarged, fang-shaped, anchored in the leaf tissue: Chromatomyia milii

13b rear spiracula normal => 14

14a puparium shining black; rear spiracula penetrating: Cerodontha muscina

14b puparium orange brown; front spiracula penetrating => 15

15a puparium monochromous orange brown; front spiraculum indistinctly bifid: Chromatomyia nigra

15b puparium yellow – orange brown with a dark ventral length band; front spiraculum fist-shaped: Chromatomyia fuscula

16a larva: rear spiraculum with 11-16 papillae; puparium in the leaf sheath: Cerodontha denticornis

16b rear spiraculum with 6 papillae at most; puparium in the blade => 17

17a the mine contains several puparia, each anchored within the mine with a strand of silk => 18

17b larva/puparium solitary, puparium not anchored in the mine: Cerodontha rohdendorfi

18a larva: the black warts at the outside of the rear spiracula small, without a “root”: Cerodontha incisa

18b these warts large, with a deep “root”: Cerodontha pygmaea

19a larva and puparium with on each segment a transverse row of long spinelike papillae: Pseudonapomyza atra

19b no such rows of spines => 20

20a larva: rear spiraculum with 12-18 papillae: Cerodontha flavocingulata

20b rear spiraculum with 6 papillae: Liriomyza graminivora

20c rear spiraculum with 3 papillae: Liriomyza flaveola