Diagnosis. S. pretiosa and S. aeneofasciella are the only two northern European Stigmella species with a proximal and a medial fascia; pretiosa has yellow head and aeneofasciella has black head. Both male and female genitalia similar to those of S. splendidissimella; see that species.
Male. Wingspan: 5.5-6.5 mm. Head: frontal tuft and vertex ochreous to orange; collar dark copper, lustrous; scape pale golden; antenna three-quarters length of forewing, grey-brown. Forewing: purplish black to dark bluish black; with two fasciae, one ill-defined, deep golden to bronzy at one fifth, and one distinct, bright golden at three-fifths; terminal cilia dark grey-brown. Hindwing and cilia grey. Abdomen dark grey, lustrous. Female. Wingspan: 5.5-6.5 mm. Antenna slightly shorter than in male. Male genitalia. Genitalia relatively large. Vinculum long; anterior margin with rather narrow emargination and broad corners. Uncus moderately long, with deep medial emargination and distinct paramedial notches. Valva markedly constricted before middle; inner margin of inner lobe expanded at midlength and set with protuberances; distal process triangular in right angle to long axis of valva. Transtilla broad, with short sublateral processes. Juxta present. Aedeagus about as long as genital capsule; with 7-12 large, pointed cornuti near tip and numerous smaller cornuti in proximal part. Female genitalia. Corpus bursae small, without pectinations. Vestibulum large and strongly swollen. Accessory sac slightly smaller than corpus bursae. Ductus spermathecae distinctly spined. Apophyses long and strong.
Host plants: Geum rivale, G. urbanum and G. montanum, Rubus fruticosus. Egg: usually on the upperside of the leaf. Larva: yellow. Mine : a long gallery usually following the veins; first half of mine narrow with frass centrally in an interrupted black line; second half of mine markedly broader with broad, diffuse frass-line. Frequently more than one mine in each leaf. In Poland, Germany and Austria all, or the majority, of the larvae hibernate in the mine; in Scandinavia all larvae vacate the mine during the autumn. Cocoon: red-brown.
From EJ and eastern Denmark, including F. In southern Sweden up to Upl. Not in Norway. In southern Finland up to Kb. - Known from few localities in Poland, Austria, Switzerland and Germany.
Voltinism: one generation per year. Mines from mid September to mid October, rarely earlier.
Description based on Johansson and Nielsen (1990)