Stigmella myrtillella

Diagnostic description: 

Diagnosis.  Almost inseparable from S. obliquella on external characters  but most specimens of obliquella lack dark blue suffusion of the forewings.  The male genitalia differ by small but constant differences in gnathos,  cornuti, and different shape of valvae.  Valva in obliquella distinctly  divided into long distal process and inner lobe.  The female genitalia of  obliquella differ from those of myrtillella in having more slender apopyses  and spined ductus spermathecae.  See also diagnosis of S. salicis.

Morphology: 

Male. Wingspan: 5.6-6.3 mm.  Head: frontal tuft pale ochreous  to ferruginous orange; collar pale yellowish; scape white; antenna slightly  longer than half length of forewing, dark grey.  Forewing: area proximal to  fascia coarsely scaled, dark grey-brown scales sometimes tipped with dark  blue or purple; fascia white to pale yellowish, oblique and usually broader  at dorsum; distal to fascia coarsely scaled, fuscous; scales tipped dark  blue or purple; terminal cilia white beyond a distinct line of dark tipped  scales, pale grey at tornus.  Hindwing and cilia pale grey.  Abdomen dark  grey with small dark grey anal tufts.  
Female.  Wingspan: 5.4-6.1 mm.  Antennae half length of forewing.  Basal half of forewing slightly darker and fascia usually more distinct  than in male.  Abdomen dark grey; ovipositor short; anal tufts broad, at  least as long as ovipositor and often covering it. Male genitalia. Vinculum plate relatively long with  distinct anterior emargination.  Uncus almost triangular with deep medial  emargination, paramedial notches distinct.  Gnathos with horizontal bar and  heavily sclerotized anterior processes forming a rectangular basal plate;  horns long, slightly diverging, close set at base; lateral arms narrow.  Valva indistinctly divided into short, pointed distal process and rounded  inner lobe with short posterior process.  Transtilla with short transverse  bar with short to moderately long and triangular sublateral processes.  Aedeagus slightly shorter than genital capsule with 3, or more rarely, 4  unilaterally sclerotized cornuti and a cluster of 4-7 spines of almost the  same length; number of cornuti and spines varying from 7 to 10. Female genitalia. Corpus bursae with dense pectinations  and distinct band of dentate, scallop-shaped chitin plates.  Ductus  spermathecae without spines.  Apophyses moderately long; anteriores broad  with short, curved anterior process; posteriores slightly shorter than  anteriores, slender.  Ovipositor slightly protruding, tip blunt.  Anal  tufts almost as long as apopyses.

Associations: 

Host plants:  Vaccinium uliginosum and V. myrtillus.  Egg:  on underside, near leaf margin.  Larva: yellow.  Mine : a narrow  gallery, closely following leaf margin 3 to 4 cm; frass as narrow, broken,  central line leaving clear margins, later it widens to a broad irregular  gallery or blotch with dispersed frass (S. Sweden, mines on V. uliginosum.)  According to Tutt (1899) and Emmet (1976), the egg is laid on the underside  close to the midrib; mine a highly contorted gallery, completely filled  with frass, finally widening to an irregular blotch, sometimes extending  along leaf margin.  Cocoon: yellowish brown. 

Distribution: 

Widely distributed in Scandinavia and Finland including  the northernmost region. - C. Europe and the British Isles.  In the Austrian  Alps up to at least 1600 m.

Life cycle: 

Voltinism: in C. Europe and  England bivoltine, in Scandinavia probably univoltine; the larvae feed from  mid-September to early October.

Citation: 

Description based on Johansson and Nielsen (1990)

Notes on description: 
S. myrtillella is much larger (5.4-6.3 mm) in Scandinavia than in C. Europe and England (4-5 mm). A very pale grey to yellowish grey form with indistinct fascia occurs in northernmost Norway: Alta.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith