Stigmella myrtillella (Stainton, 1857)
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.
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.
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.
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.
Voltinism: in C. Europe and England bivoltine, in Scandinavia probably univoltine; the larvae feed from mid-September to early October.
Description based on Johansson and Nielsen (1990)
