Stigmella microtheriella (Stainton, 1854)
Diagnosis. The combination of the narrow forewings, short antennae and, usually, a distinct fascia on the underside of the forewings which extends over costal cilia, distinguish microtheriella from S. betulicola and S. luteella. The female genitalia are characterised by the short ductus spermathecae and one signum being markedly smaller and more posterior than the other.
Male. Unknown. Female. Wingspan: 3.5-4.8 mm. Head: frontal tuft ochreous yellow, sometimes mixed yellowish brown; collar and scape white or yellowish white; antenna distinctly shorter than half length of forewing. Forewing narrow; area proximal to fascia purple fuscous to bronzy brown; fascia postmedial, white to pale yellow; fascia often slightly constricted at midlength; distal to fascia dark purple fuscous; terminal cilia of same colour as distal part of wing, tips paler. Hindwing: greyish brown; cilia pale grey. Abdomen fuscous.
Female genitalia. Corpus bursae almost completely covered with pectinations which may be indistinct in anterior half. Ventral signum approximately twice as long as dorsal signum and in a markedly more posterior position. Ductus spermathecae relatively short.
Host plants: Carpinus betulus, Carpinus orientalis, Corylus avellana, Corylus colurna and several cultivated species of Carpinus and Corylus and Ostrya carpinifolia in southern Europe. Egg: on lower surface of leaf, usually close to a rib. Larva: very pale greenish yellow to almost colourless; head pale red-brown. Mine: on Corylus a 12-15 cm long very narrow, irregular gallery with frass throughout the mine in thin central line. On Carpinus shorter and broader, often close to a rib and frass-line more diffuse. Cocoon: yellowish to pale brown.
Widely distributed in Denmark and Fennoscandia to about 62` northern latitude. - Its range includes Ireland and North Spain in the west, western USSR in the east and Italy, Greece and the Caucasus in the USSR to the south. S. microtheriella has been introduced into New Zealand.
Voltinism: two generations per year in northwest Europe.
Description based on Johansson and Nielsen (1990)
