Diagnosis. Both sexes very similar to the slightly larger S. lemniscella but the male differs from lemniscella in having smaller scape, not edged with black and less conspicuous androconial scales on the hindwings; the female in having darker collar and blunt abdominal tip. Also S. continuella and S. aurella are very similar but lack androconial scales on the hindwings; the female of continuella has a yellowish collar; both have more pointed abdominal tips. The male and female genitalia of speciosa do not resemble those of any other European Stigmella species.
Male. Wingspan: 4.5-5 mm. Head: frontal tuft black, often mixed with yellow; collar black; scape white; antenna half length of forewing or slightly longer. Forewing: proximal to fascia shining greenish golden, shading into dark purplish brown before fascia, fascia strongly shining, silver to pale gold, broader at dorsum, distal to fascia purplish black; terminal cilia dark grey brown, slightly paler at tips. Hindwing: grey-brown with long, black hair scales along costa and dorsum extending over cilia to at most half length; cilia grey-brown. Abdomen: fuscous with some blue and purplish suffusion. Female. Wingspan: 4.8-5.5 mm. Frontal tuft pale ochreous to ferruginous, sometimes mixed with black; collar brown; antenna half length of forewing or slightly shorter. Forewing proximal to fascia brownish gold shading into dark purplish brown at fascia. Hindwing and cilia grey brown, without androconial scales. Male genitalia. Vinculum very wide, anterior emargination shallow; lateral corners rounded. Uncus distinctly bilobed, each lobe with deep medial notch. Gnathos with large rounded anterior processes and relatively short almost parallel horns. Valva small; distal process long and almost straight; inner lobe very short, posteriorly rounded. Transtilla with short, slender transverse bar and short, triangular sublateral processes. Aedeagus distinctly longer than genital capsule with large square chitin plate at tip; vesica almost completely covered with large triangular cornuti, the largest near tip of aedeagus. Female genitalia. Bursa large, almost globular, posteriorly well sclerotized with many longitudinal folds. Ductus spermathecae very long and thin, without spines. Apophyses widely separated; posteriores longer than anteriores. Abdominal tip blunt.
Host Plants: Acer pseudoplatanus, monspessulanum and possibly other S. European Acer species; not found on Acer platanoides and campestre; mines on these species belong to S. aceris. Egg: is always laid on the underside of leaf, away from ribs or margin. Larva: pale yellow. Mine : very variable depending on thickness of leaf; in thin leaf a long sinuous gallery with frass throughout as a thin central line leaving wide clear margins; in thick, sun-exposed leaf a short gallery almost filled with frass. Cocoon: yellowish brown to dark brown.
Erroneously reported from Sweden and Norway. - The northernmost confirmed records are from SE. England, the Netherlands, N. Germany and SW. Poland. It has a wide distribution in C. and SE. Europe and Italy.
Voltinism: in S. Europe bivoltine; in England mainly univoltine. Feeding larvae in July-August and again in September-October. Some of the earliest larvae become adults in August; the rest hibernate and produce adults in May.
Description based on Johansson and Nielsen (1990)