1a tentiform mine, or a blotch without a long initial corridor => 2

1b mine begins as a narrow corridor, that may or may not widen further on; the corridor can be short and tortuous => 19

1c fleck mine => 27

1d mine ends in an oval or circular excision => 35

1e whitish transverse connection between midrib and a lateral vein, or between two veins, usually not far from the leaf tip: Heliozela resplendella

1f gallen etc => Tabellen voor alle parasieten per soort

2a circular blotch with frass in concentric arcs around a dark centre: Leucoptera malifoliella

2b mine different, frass not in concentric arcs => 3

3a large blotch; (almost) full dephth, transparent => 4

3b small blotch of evident tentiform mine, never transparent => 9

4a underside of leaf with a loose spinning, in which frass grains are trapped; larvae crimson: Atemelia torquatella

4b no spinning, ground colour of larvae whitish => 5

5a frass in long threads: Paracrania chrysolepidella

5b frass in loose grains => 6

6a thoracic feet of the larva reduced to black triangular stumps** (well visible with a hand lense, without opening the mine): Heterarthrus vagans

6b thoracic feet rather slender**, almost colourless => 7

7a larva: in front of all abdominal prolegs a black crescent-shaped spot; on Alnus viridis: Scolioneura betuleti

7b abdominal prolegs without spots => 8

8a larva: thorax-segments 1-3 and abd. 1 ventrally with a black spot; exclusively on Alnus viridis: Fenusa pumila

8b thorax-segments 1-3 and abd. 1 ventrally with almost imperceptible pigmentation; also on Alnus viridis: Fenusa dohrnii

9a mine upper-surface => 10

9b mine lower-surface => 11

10a silvery blotch without a fold: Caloptilia elongella

10b yellow-green tentiform mine with 1 longitudinal fold: Phyllonorycter stettinensis

11a lower epidermis of the (fresh) mine brown; mine small (ca. 1 cm), usually at the leaf margin: Caloptilia falconipennella

11b lower epidermis yellow-green or yellow, usually larger, not necessarily at the leaf margin => 12

12a lower epidermis with 1, strong, fold => 13

12b lower epidermis with numerous weak folds => 14

13a species from almost all Europe; pup: abd. 7 ventrally with group of about 3+3 spines, directed outwards: Phyllonorycter rajella

13b species from southern Europe (France, Italy); pupa: this group of spines may be missing: Phyllonorycter vulturella

14a mountain species, on Alnus viridis => 15

14b lowland species, on other Alnus spexies => 16

14c of Phyllonorycter alnivorella, a species from south-western Europpe, mine and pupa are not sufficiently known

15a central European mountain species, on op Alnus viridis: Phyllonorycter alpina

15b species of the mountains of Corsica, on Alnus viridis subsp. suaveolens: Phyllonorycter suaveolentis

16a pupa: cremaster with two pairs of spines (the inner pair much the shortest); abd7 ventrally with a small group of outwards pointing spines => 17

16b only the outer pair of crremaster spines present; ab7 without a ventral group of spines => 18

17a only on Alnus incana; pupa: rear angle of metanotum with a pit; 7th abdominal segment ventrally with 3+3 outward directed spines; mine contracted stronger than in the much more common klemannella: Phyllonorycter strigulatella

17b on Alnus glutinosa and incana; pupa: rear margin of metanum without a pit; 7th abdominal segment ventrally with 1+1 outward directed spine: Phyllonorycter klemannella

18a mine remarkably large; in vacated mines the exuvium generally protrudes through the lower epidermis; larva grey; species from almost all Europe: Phyllonorycter froelichiella

18b mine not that large; in vacated mines the exuvium always protrudes through the upper epidermis; larva unknown; species from SW Europe: Ph. chrysella

19a mine begins in midrib or a thick lateral vein => 20

19b mine begins freely in the leaf disc => 23

20a corridor short (1-2 cm), narrow, not widening, may run form one vein to another; no oviposition scar visible: young mine of Heliozela resplendella

20b corridor long, mor or less widening; deep oviposition scar in midrib or vein => 21

21a corridor widening just enough to accomodate the growing larva: Anoplus plantaris & A. roboris

21b corridor suddenly widening into a blotch, usually in the leaf apex => 22

22a leaf apex crumpled; initial corridor ca. 1 mm wide; larva in May-June: Orchestes testaceus

22b leaf apex normal; initial corridor wider; larva in June-August: Orchestes jota, Tachyerges pseudostigma & T. stigma

23a short, strongly contorted corridor, quickly widening into blotch: Ectoedemia minimella

23b corridor not cotorted, little of no widening => 24

24a corridor upper-surface, gradually widening, usually strongly discolouring the leaf: Agromyza alnivora

24b corridor full deep, hardly widening, hardly discolouring the leaf; at the start of the mine a tiny egg shell => 25

25a corridor short (< 3 cm); larval chamber > 3x its width; egg shell iridescent; exit slit upper-surface: Bucculatrix cidarella

25b corridor longer; larval chamber < 3x its width; egg shell shining; exit slit lower-surface => 26

26a frass line 1/3 – 1/2 of the width of the corridor; often several mines in a leaf; larva yellow, with a grey prosternum: Stigmella glutinosae (vacated mines usually cannot be distinguished with certainty form those of the following species)

26b frass line not wider than 1/3 of the corridor width; mines usually single; larva pale yellow, including the prosternum: Stigmella alnetella

27a hole in the mine not neatly circular; case helicoidal: Apterona paludella

27b hole circular; case more or less tubular => 28

28a case untidy, resembles a dead leaf: C. siccifolia

28b case different => 29

29a pistol case: Coleophora anatipenella

29b case small (ca. 3 mm), strongly curved, hooklike: juvenile case of Coleophora serratella

29c case > 5 mm, straight or weakly curved => 30

30a case made of 1 folded and spun leaf fragment => 31

30b composite leaf case => 33

30clobe case => 34

31a case three-valved, about 7 mm lang, rather squat; the commonest Coleophora on Alder: Coleophora serratella

31b case two-valved => 32

32a full-grown case about 8 mm: C. milvipennis

32b case about 13 mm: Coleophora alnifoliae

32c case 9-12 mm; on Alder probably only xenophagous: C. limosipennella

33a the leaf fragments of the case remarkably precisely fit to each other: Coleophora orbitella

33b these leaf fragments untidily connected: Coleophora binderella

34a case strongy bent; behind the mouth a number of rings: Coleophora fuscocuprella

34b case not bent, or only a little near its end; no rings behind the mouth: C. violacea

34c in the literature also Coleophora ahenella, of which the case cannot reliably be separated from the previous, is often reported from Alder; possibly this is due to identification errors

35a excision elliptic, ca. 3 x 5 mm: Heliozela resplendella

35b excision circular, ca. 5 mm in diameter: Incurvaria pectinea