Stigmella trimaculella (Haworth, 1828)
Diagnosis. The conspicuous orange male abdomen is distinctive and not paralleled by other Stigmella species. The three large forewing spots in combination with pale yellow cilia are good characters for identification of females.
Male. Wingspan: 5.4-6.0 mm. Head: frontal tuft ochreous to pale brownish; collar and scape yellowish white; antenna half length of forewing, pale grey-brown. Thorax fuscous; front, sides and tegulae yellowish white. Forewing: coarsely scaled, dark grey-brown; a broad, elongate basal spot and two opposite spots at two thirds from wing-base, pale yellow. Spots often very large and confluent, reducing the dark ground colour more or less, sometimes to a narrow streak along costa and a small apical spot. Terminal cilia pale yellow, pale grey at tornus. Hindwing: pale yellow, shading into grey at apex; cilia similarly coloured. Abdomen yellowish orange. Female. Wingspan: 5.5-6.0 mm. Frontal tuft pale grey- brown. Hindwing and cilia grey. Abdomen grey-brown with short similarly coloured anal tufts. Male genitalia. Vinculum plate broad with moderately deep anterior emargination. Uncus triangular with triangular medial emargination, paramedial notches indistinct or absent. Gnathos with close-set, diverging horns on relatively small basal plate. Valva divided into long and strong distal process and pointed inner lobe. Transtilla with narrow transverse bar and moderately long sublateral processes. Aedeagus distinctly shorter than genital capsule with 3-4 small cornuti and a cluster of 8-10 straight spines. Female genitalia. Corpus bursae elongate with band of elongate chitin plates; large parts of corpus densely covered with pectinations. Ductus spermathecae without spines. Apophyses equally long. Ovipositor not protruding, tip blunt.
Host plants: Populus nigra, P. alba, P. canadensis-hybrids and various cultivars. Egg: laid on either side of leaf but appears to be commoner on upper side. Larva: pale greenish yellow. Mine : variable, first half narrow, usually following a rib for some distance, second half considerably wider, sometimes forming an elongate blotch. Frass variably deposited depending on thickness of leaves; in first half usually broken linear, leaving clear margins; in second half varying from a thin central line to a broad band or patches. Cocoon: brown to red-brown.
In eastern Denmark and EJ.; southern Sweden to Upl.; southern Finland from Al to Ta. and Sb.; Norway VAy. - Widely distributed in central and eastern Europe, northern Italy, Corsica and England.
Voltinism: bivoltine; larvae in July and from early September to early October. Adults in June and August.
Description based on Johansson and Nielsen (1990)
