Figs. 14–16, 66– 67, 93
Elachista bruuni Traugott-Olsen, 1990: 48.
Material studied. Type material. Holotype ♂ labelled: Holotype (rounded with red margin); [Finland] Hang; 7.7.69; genital praeparat nr. A 27.6. 87, sex ♂ E. Traugott-Olsen; Forwing [sic] praeparat nr. A 28.6. 87, sex ♂ E. Traugott-Olsen NMH; Hindwing praeparat nr. A 28.6. 87, sex ♂ E. Traugott-Olsen; Holotype Elachista bruuni Traugott-Olsen (MZH). Other material. Finland: N. Hanko peninsula, 200 exx in MZH, with genital slides: Genital praeparat C 27.8. 87, G, H, I, 27.6. 87, E. Traugott-Olsen, L. Kaila prep. 480, 481, 3074–3077, 3081 (MZH). Estonia: Piusa, 7. VII. 2984, 2 ♂, K. Nupponen leg. (Coll. Nupponen); Saaremaa, Pidula, 23. VII. 1983, 2 ♂, K. Nupponen leg., L. Kaila prep. 1451 (Coll. Nupponen, MZH). Latvia: Carnikava, 2. VI. 2000, 5 ♂, 1 ♀, Junnilainen leg., L. Kaila prep. 3466 (Coll. Junnilainen, MZH). Russia: Karelia, Olonets region, Vidlitsa, 19. VI. 1991, 14 ♂, L. Kaila, J. Kullberg & P. Martikainen leg., L. Kaila prep. 482–484, 3079, 3080; C 20.12. 94 E. Traugott-Olsen (MZH).
Diagnosis. Elachista bruuni is a white species with two brown spots; sometimes the plical spot is faint or absent. Distinguishing it from similar species such as E. dispilella and E. distigmatella requires an examination of the genitalia. The uncus lobes of E. bruuni are narrow, reminiscent of those of E. nitidulella; the cornuti are larger than those of E. distigmatella and smaller than those of E. dispilella. Elachista bruuni is easiest to distinguish from E. nitidulella by their outer appearance; E. nitidulella is smaller, the forewing unicolorous dirty white, and the hindwing darker grey than in E. bruuni. The male genitalia of the two are similar; the valva is a little longer and the cornutus group larger in E. bruuni than in E. nitidulella. The juxta lobes are strongly produced laterally in E. bruuni, not so in E. nitidulella. For female genitalia, see the key.
Molecular characterization. The analyzed seven specimens of E. bruuni showed a maximum variability of 0.15 %. Average distance between the specimens was 0.04 %. The genetically closest species was E. ripai with 5.56 % minimum distance to E. bruuni.
Redescription of genitalia. Male genitalia. Uncus lobes narrow, tapered towards pointed and outward bent apex, length 2.5 times as long as wide at their widest point, sickle-shaped, mesial margin convex, lateral margin concave, rounded. Spinose knob of gnathos oval-shaped. Valva nearly 1.4 times as long as tegumen + uncus, 4.5 times as broad as long, parallel-sided; base of sacculus somewhat dilated; cucullus elongate. Digitate process tongue-shaped, 0.2 times as long as valva, medially and distally with stout setae. Juxta lobes distinctly laterally produced, mesial margin slightly convex, joining the straight distal margin in an obtuse angle. Phallus as long as valva, bent, nearly parallel-sided; cornutus cluster elongate group formed of less than ten spines, basal ones somewhat shorther than distal ones; length of longest spines abouth equal to diameter of phallus.
Female genitalia. Apophyses posteriores slender, straight, 1.5 times as long as papillae anales. Apophyses anteriores about half the length of apophyses posteriores. Ostium bursae invaginated in sternum 8, rounded; colliculum as wide as ostium bursae with elongate lateral sclerotizations; ductus seminalis narrow, granulose, distance between its inception and ostium bursae equal to length of apophyses posteriores; ductus bursae 5 times as long as apophyses posteriores, tubular, membranous, granulose, particularly so in anterior half, apart from the most anterior 1 / 5, incepted in corpus bursae with distinct border; corpus bursae large, pyriform, with small internal granules in median zone; signum narrow and long, dentate, boomerang-shaped.
Biology. Elachista bruuni inhabits sandy habitats, often dunes. It has been reared from Festuca polesica (J. Junnilainen, personal communication). In Russia adults were found on F. ov i n a, which is likely another hostplant. Adults climb onto the host plants before sunset and where they are easily observed. Occasionally they are also attracted to artificial light.
Distribution. Estonia, Finland, Latvia, Russia, Sweden (Svensson 2006).