Nepticula aceris, Stigmella aceris, Stigmella, Nepticula

Diagnostic description: 

Diagnosis.  S. speciosa (Frey) (also on Acer) differs from aceris  males by the presence of androconial scales on the hindwing and the greenish  golden base of the forewing and in the females by the ferruginous head.  S. crataegella also resembles aceris, but differs by usually smaller size  and more brightly coloured forewings and, in the male, fuscous hindwings  with short androconial scales along costa and dorsum.  Male genitalia  characterized by the combination of two distal processes on valva and the  presence of a juxta.  Female genitalia can be easily distinguished from  species outside aceris group by the band of small spines near accessory sac  and broad and blunt apophyses anteriores; the medial process on tergum VIII  is present in only prunetorum and aceris among the northern European species.

Morphology: 

Male.  Wingspan: 3.7-4.9 mm.  Head: frontal tuft dark fuscous; collar  large, white; scape large, white; antenna shorter than half length of  forewing.  Forewing: area proximal to fascia golden fuscous with purple  tinge near costa; fascia postmedial, silvery to pale golden, sometimes  ill-defined or altogether absent; distal to fascia dark purplish brown  often with a few dark blue scales; terminal cilia concolorous but paler at  tips.  Hindwing: pale grey. Female. Wingspan: 4.3-4.7 mm.  Head: antenna distinctly  less than half length of forewing.  Otherwise similar to male. 
Male genitalia. Vinculum with distinct lateral  corners.  Tegumen slightly wider than uncus.  Uncus with hind margin slightly  emarginate, margins well sclerotized.  Gnathos with very long transverse  bar, long horns and distinct anterior processes.  Valva with narrowly  pointed inner lobe, one short distal process at ventral side and one longer,  arcuate distal process at dorsal side.  Transtilla with long, outwardly-curved  sublateral processes.  Anterior margin of juxta with distinctly more sclerotized  bar.  Aedeagus approximately 1.3 to 1.5 times length of genital capsule;  vesica with numerous close-set very small, blunt cornuti and pointed or bidentate spines. Female genitalia. Corpus bursae with band of small  spines near accessory sac.  Accessory sac small.  Apophyses anteriores  unusually broad and blunt, distinctly shorter than apophyses posteriores, 
which are long and thin.  Posterior margin of tergum VIII prolonged medially  into pointed posterior process.

Associations: 

Host plants:  Acer campestre, A. platanoides, A. tataricum;  records from A. pseudoplatanus are probably based on misidentifications of  S. speciosa.  Egg: usually on underside of leaf, occasionally on upperside.  Larva:  green.  Mine : long, narrow, sinuous gallery, filled  with coiled greenish frass, rarely leaving narrow clear margins; in last  centimetre of mine frass becomes darker and more or less linear; exit-hole  on upperside.  Fresh mines are hard to find, since frass and larva have  approximately same colour as leaf; in withered mines frass becomes brown.  Easy to separate from S. speciosa, which not only feeds on different species of Acer, but also its black frass leaves clear margins in speciosa.  Cocoon:  brownish. 

Distribution: 

In Denmark only from LFM; in eastern Sweden up to Gstr.  In Norway only from Oslo and Drammen; absent from Finland. -  Widespread  and common in central and southern Europe, becoming more local towards the  northwest.  Very local in south England.  Not found in The Netherlands and  Belgium.  Distribution shown by Schoorl et al.  (1985). 

Life cycle: 

Voltinism:  bivoltine, trivoltine in southern Europe.  

Citation: 

Description based on Johansson and Nielsen (1990)

Notes on description: 
Nepticula aceris Frey. Holotype examined by Schoorl et al. (1985: 99). Nepticula szocsi Klimesch was synonymized by Klimesch (1978: 246, 248). N. szocsi represents the form of aceris without a fascia. This form is not known from northern Europe.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith