Alnus, alder

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 => 100

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, transparant => 4

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

100a Nematoda => 101

100b Acari => 102

100c Coleoptera => 103

100e Diptera => 104

100f Hemiptera => 105

100d Hymenoptera => 106

100g rust fungi => 107

100h smut fungi => 108

100i powdery and downy mildews => 109

100j other causers => 110

103 – Coleoptera

103a Cerambycidae: Oberea linearis

103a Curculionidae: Cryptorhynchus lapathi

104 – Diptera

104a Cecidomyiidae: Dasineura tortilis; Jaapiella clethrophila; Macrolabis alnicola

105 – Hemiptera

105a Diaspididae: Chionaspis salicis

105b Psyllidae: Psylla alni

107 – rust fungi

107a Pucciniastraceae: Melampsoridium betulinum, hiratsukanum

109 – powdery and downy mildews

109a Erysiphaceae: Erysiphe penicillata, vernalis; Phyllactinia alnicola

109b Peronosporaceae: Phytophthora alni

110 – other causers

110a Bacteria, Frankiaceae: Frankia alni

110b Bacteria, Rhizobiaceae: Agrobacterium tumefaciens

110c Fungi, Capnodiales: Cladosporium alneum

110d Fungi, Taphrinaceae: Taphrina alni, epiphylla, sadebeckii, tosquinetii, viridis

110e Lepidoptera, Heliozelidae: Heliozela resplendella

110f Lepidoptera, Tortricidae: Epinotia immundana, tenerana, tetraquetrana

110g Lepidoptera, Yponomeutidae: Argyresthia brockeella, goedartella

110h Plantae, Santalaceae: Viscum album

**Vacated mines still contain the exuvia; usually the difference in structure of the feet can be clearly seen there as well.

The following species have been recorded from Alnus in the literature, but the identifications seem dubious: Orchestes alni (Kollár, 2007a), Phyllonorycter corylifoliella (Hartig, 1939a), Rhamphus pulicarius (Roques, 1998a).

Not included in the key: Bucculatrix thoracella; Eriocrania alpinella; Fenusella nana.