Nepticula alnetella, Stigmella alnetella, Stigmella, Nepticula

Diagnostic description: 

Diagnosis.  S. alnetella is easily separated from all other species  of the betulicola group by its metallic shining forewings, and from the  Betula-feeding S. continuella by its dark collar (continuella has the  yellowish white collar).  In the male genitalia the two horn-like processes  from the uncus are characteristic.   The prominent sinuous structure in segment VIII separates the female genitalia of alnetella from those of  all other species.  

Morphology: 

Male. Wingspan: 3.9-4.5 mm.  Head: frontal tuft ferruginous;  collar dark bronzy fuscous; scape shining yellowish white, usually edged  with silvery to metallic grey; antenna longer than half length of forewing.  Forewing: area proximal to fascia metallic dark brown to almost black,  dorsum coppery brown to golden; fascia postmedial, shining silvery; distal  to fascia dark purple fuscous; terminal cilia of same colour as distal part  of wing, tipped silvery grey at apex.  Hindwing grey with silvery-tipped  cilia at apex.  Abdomen dark fuscous. 
Female.  Wingspan: 4.3-4.8 mm.  Head: scape yellowish white, without  grey edge; antenna approximately half length of forewing.  Otherwise similar  to male. 
Male genitalia. Vinculum with V-shaped emargination.  Uncus with posterior corners produced into distinctly pointed processes.  Gnathos with long horns.  Tegumen broad, margin dentate.  Valva with distal  half narrow.  Transtilla bilobed, ventral arms absent.  Aedeagus small. Female genitalia. Corpus bursae almost completely covered  with prominent pectinations.  Segment VIII with prominent, strongly  sclerotized, sinuous structure.

Associations: 

Host plants:  Alnus glutinosa, A. viridis and A. cordata,  occasionally also on Betula.  Egg: on lower surface of leaf, close to a  rib.  Larva: pale yellow without distinct spot on prothorax; with green  intestine and pale brownish head.  Mine: a long slender gallery  towards margin of leaf, frequently following a vein or the margin of the  leaf.  Frass throughout as a thin central line occupying approximately  one-third width of mine.  Mines of both alnetella and S. glutinosae very  similar and it is not possible to separate the vacated mines.  Cocoon: pale  brown.

Distribution: 

Widely distributed in Denmark and Fennoscandia up to  about 52` northern latitude. -  The range includes England and Scotland in  the west, western USSR in the east and Corsica, Italy and the Caucasus  in the USSR to the south.

Life cycle: 

Voltinism: two generations per year in south and central  Europe; only one generation known from Scandinavia.  S. alnetella seems to  be the rarest of the Alnus-feeding nepticulids in Scandinavia.  

Citation: 

Description based on Johansson and Nielsen (1990)

Notes on description: 
Nepticula alnetella Stainton. Lectotype designated by Schoorl & Wilkinson (1986: 235).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith