Diagnosis. B. quadrimaculella can be easily recognized by size, postmedial spots, purplish gloss, absence of cilia-line and collar with lamellar scales, but see also B. auriciliella. Male genitalia differ from other Bohemannia species by size, shape of valva and gnathos and complex aedeagus. Female genitalia characterized by rectangular, extending ovipositor and distinct, long signa.
Male. Wingspan: 7.4-8.5 mm. Head: frontal tuft yellowish orange to ferruginous; collar shining fuscous, small, comprising lamellar scales; scape pale shining golden, flagellum fuscous, but terminal 11-12 segments yellowish white; antenna with 50-57 segments. Thorax coppery fuscous, with purple reflections. Forewing shining coppery brown with purple reflections; pale golden spot on costa and dorsum beyond middle, dorsal spot larger than costal; cilia-line absent, tips of terminal cilia grey fuscous. Hindwing: fuscous, a short dark brown hair-pencil of one-sixth hindwing length near frenulum, costal bristles absent. Anal tufts grey.
Female. Wingspan: 8.0-8.8 mm. Antenna with 44-46 segments. Venation. R1 separate. R+M+Cu comprising 6 branches: R2+3, R4, R5, M1, M2 and Cu. Male genitalia. Vinculum slightly concave anteriorly. Tegumen not forming pseuduncus, truncate. Uncus band-like, without medial projection, with two lateral setose pads. Gnathos with very long, narrow central element. Valva widest at base, suddenly narrowed beyond middle, tip curved inwards, pointed; a tongue-shaped dorsal projection, from outer margin inwards. Aedeagus carinate processes complex: a long narrow ventral carina with bifid tip; a pair of lateral, serrate carinae; vesica with many small, triangular cornuti and one very long, smooth cornutus. Female genitalia. Terminalia narrow, extending from segment VII. T VIII narrow, posteriorly excavate, with two groups of setae, no scales; anal papillae distinct, separate, with more than 20 setae each; S VIII with parallel margins, giving the terminalia a rectangular shape. Vestibulum with lateral, folded sac and two internal, spine-like sclerotizations; corpus bursae covered with small spines, placed in groups of three on small cushions; signa elongate, with incomplete cells. Ductus spermathecae with 8 convolutions.
Host plant: Alnus glutinosa. The biology of this species is insufficiently known. Emmet (1970) reported a possible mine in a shoot of Alnus, but since this mine was silk-lined, a feature unknown in any nepticulid, it is not likely to belong to this species. Later, Emmet (in litt.) found a yellow nepticulid larva, almost certainly of this species, when he opened a bud of Alnus without any outer sign of feeding.
A local species, not found in Finland and Norway. In Denmark from NEZ, F, LFM and S, in Sweden only from Hall., Sk. and Bl. - In Ireland from three counties, local in England, Scotland and Wales and the Netherlands; in Belgium only known from Bergh. Also from West Germany (see note), France (three records), Austria and Rumania. One specimen taken in Japan, Hokkaido (leg. Kumata) could also belong to this species.
Voltinism: Adults are frequently taken by beating alders in July and August.
Description based on van Nieukerken and Johansson (1990)