Stigmella tristis (Wocke, 1862)
Diagnosis. Small size, dark head and unicolorous forewings separate tristis from all other species occurring in northern Scandinavia.
Male. Wingspan: 4-5 mm. Head: frontal tuft dark grey- brown to almost black; collar and scape yellowish white to pale grey; antenna slightly longer than half length of forewing. Thorax dark bronzy- brown. Forewing: yellowish or greyish bronze with faint metallic lustre; extreme base concolorous with thorax; terminal cilia grey-brown. Hindwing and cilia grey. Abdomen: fuscous with grey-brown anal tufts.
Female. Wingspan: 4-5 mm. Frontal tuft ferruginous to dark brown; antennae half length of forewing. Hindwings and cilia pale grey. Male genitalia. Vinculum with anterior emargination varying from shallow to deep. Uncus with two long, triangular projections. Gnathos with relatively short horizontal bar and long horns. Valva divided into extremely large, rounded inner lobe and thin, curved distal process. Transtilla with long transverse bar and short sublateral processes. Aedeagus as long as genital capsule with numerous spines and cornuti of varying sizes, the longest near base. Manica large, densely covered with minute spines.
Female genitalia. Vestibulum long and wide, partly with strong sclerotizations. Corpus bursae reduced. Accessory sac small and asymmetrical with spined sclerotizations and a band of spines extending into vestibulum. Ductus spermathecae anteriorly and posteriorly 2 to 3 times convoluted. Apophyses anteriores with broad posterior part and slender anterior process; posteriores of approximately the same length and straight.
Host plant: Betula nana. Egg: on upperside of leaf, large and yellowish brown. Larva: yellowish green. Mine : a short contorted gallery, terminating part wide, sometimes forming a small blotch; frass brown (only few mines examined). Cocoon: dark brown.
Known only from a few localities in northernmost Scandinavia; Sweden: Hrj., P.Lpm. and T.Lpm.; Finland: Le and Norway Fv and Fn.
Voltinism: univoltine; depending on weather conditions and altitude, adults have been collected from the middle of June to the middle of July but the actual period is probably short. Mining larvae collected from about July 20th to the beginning of August. Habitat: arctic species, occurring in bogs, mainly in the subalpine region.
Description based on Johansson and Nielsen (1990)