Diagnosis. Very similar to S. mespilicola, from which it can be separated by paler, unicolorous proximal half of forewing and paler and distinctly violet distal part of forewing. It differs from S. crataegella (also on Crataegus) by its larger size and paler forewing colour. In male genitalia hybnerella differs from S. mespilicola in having longer lateral corners of vinculum, uncus without protuberances, longer valva with shorter distal process, transtilla with longer processes and longer aedeagus. In the female genitalia of hybnerella the accessory sac is distinctly longer than corpus bursae, while in S. mespilicola corpus bursae is markedly longer than accessory sac.
Male. Wingspan: 4.5-5.5 mm. Head: frontal tuft and vertex black, rarely brown or yellowish; collar small, black to grey-brown; scape white; antenna shining grey, as long as or slightly longer than half length of forewing. Thorax concolorous with base of forewing. Forewing narrow; area proximal to fascia pale golden brown to bronzy brown, strongly shining, base of costa slightly darker; fascia distinctly postmedial, shining silvery to pale golden; distal to fascia violet to purplish brown; terminal cilia brown, shading into pale grey at tips. Hindwing: grey-brown, basal two-thirds with dark grey-brown to bluish black scales and at costa and dorsum brownish to bluish black androconical scales extending over cilia to at most one-fifth. Cilia grey-brown. Abdomen: fuscous with some metallic scales.
Female. Wingspan: 4.5-5.5 mm. Head: frontal tuft varying from black to orange; collar small, dark grey-brown to silvery white or yellow in orange-headed specimens. Hindwing cilia dark grey, without androconial scales. Male genitalia. Genital capsule distincly longer than wide. Vinculum with anterior margin deeply excavated, lateral corners narrow. Uncus very broad, hind margin straight without distinct protuberances.
Gnathos with long and slender transverse bar; horns widely separated, long and pointed, anterior processes small. Valva with very short distal process, reaching base of uncus, and large posteriorly rounded inner lobe, usually reaching hind margin of uncus. Transtilla with long and slender sublateral processes. Aedeagus 1.4-1.6 times length of genital capsule, vesica with long band of several hundred elongate, sharply pointed cornuti and small spines; distal portion with 3-6 triangular cornuti. Female genitalia. Corpus bursae small, without pectinations. Accessory sac markedly longer than corpus bursae, three-quarters length of abdomen, with 6-7 convolutions. Ductus spermathecae shorter than accessory sac.
Host plants: in Scandinavia only known from Crataegus; in central and southern Europe also on Sorbus aria, S. torminalis, Amelanchier ovalis and Cotoneaster. Egg: on any part of the leaf, both on upperside and underside. Larva: almost colourless to very pale green. Mine : first 1.5-2.0 mm a long narrow gallery with frass in a narrow central line leaving clear margins; second half widening to an elongated, irregular blotch with frass in a line or irregularly dispersed. Cocoon: dark red to red brown.
From several districts in Denmark and in Sweden up to Upl. Not in Norway; we cannot confirm Grönlien's (1932) records. From southwest Finland. - Widely distributed throughout Europe.
Voltinism: in Scandinavia two generations per year, with the possibility of a third generation in southern Europe. Larvae of the summer generation appear relatively early, in Scandinavia from mid-June, in Holland from late May.
Description based on Johansson and Nielsen (1990)