Stigmella unicaudata Remeikis & Stonis, sp. nov.

(Figs 1, 36–48)

Type material. Holotype: ♂, ARGENTINA, Chubut, Esquel, SE of Lago Futalaufquen, elevation ca . 600 m, 2.i.1982, Nielsen & Karsholt, genitalia slide no. RA444♂ (ZMUC). Paratypes: 9 ♂, 4 ♀, ARGENTINA, Neuquen Province, San Martin de los Andes, elevation ca . 640 m, 29.ix.–15.xi.1981, some collected on Azara microphylla Hook. f., Nielsen & Karsholt, genitalia slide RA280♀, RA292♂, RA294♂, RA299♀, RA312♀, RA313♀, RA314♀, RA315♀, RA316♀, RA317♀, RA319♀, RA626♂ (with some leaf-mines on Azara microphylla Hook. f., Salicaceae, 20.ix–1.x.1981); 2 ♂, Río Negro Province, San Carlos de Bariloche, Camino del Tronador, elevation ca . 800 m, 29.xi.1978, Mision Cientifica Danesa, genitalia slide RA293♂, RA608♂ (ZMUC); 1 ♂, same, Colonia Suiza, 22.xi.1978, Mision Cientifica Danesa, genitalia slide no. RA 595♂ (ZMUC) .

Diagnosis. The combination of a gnathos with one wide caudal process, deeply divided uncus, valva with two apical processes, and a silvery shiny fascia of forewing distinguishes S. unicaudata sp. nov. from all other Stigmella, including the most similar S. decora sp. nov.

Male (Figs 36, 37). Forewing length 2.1–2.2 mm; wingspan about 4.7–4.9 mm. Head: palpi pale greyish cream to brownish cream; frontal tuft grey beige to fuscous brown; collar and scape cream to silvery or golden cream; antenna slightly longer than half the length of forewing; flagellum with 37–42 segments, brown-black with golden gloss on upper side and underside. Thorax and tegula golden brown. Forewing: golden brown on basal 2/3 (before fascia), dark brown with golden gloss and very light purple iridescence on apical third (beyond fascia); fascia postmedian, silvery shiny; fringe grey or brown-grey to pale grey, sometimes with some overlapping, silvery shiny scales; underside of forewing grey-brown, without spots. Hindwing grey to brownish grey on upper side and underside, without spots or androconia; its fringe grey-brown. Legs brownish grey, glossy. Abdomen fuscous grey on upper side, dark grey to grey on underside.

Female (Figs 38, 39). Forewing length 2.5–2.6 mm; wingspan about 5.5–5.8 mm. Flagellum with 28–32 segments, dark grey to black-brown on upper side, grey to dark grey on underside, with some purple iridescence. Silvery shiny fascia of forewing very wide and straight; area beyond fascia dark brown with strong purple iridescence. Abdomen grey to grey-brown on upper side, yellowish cream with some orange-yellow scales on underside; abdominal tip (genital segments) distinctly narrower that other segments, setose. Otherwise as in male.

Male genitalia (Figs 40–43). Capsule longer (305–310 µm) than wide (185 µm). Uncus with two narrow triangular lobes. Gnathos with one wide caudal process; distally caudal process weakly tickened, rounded or truncated. Valva 180 µm long, 65–70 µm wide, with two apical processes; transtilla without sublateral processes. Vinculum with large lateral lobes and short ventral plate. Phallus (Figs 42, 43) 265–315 µm long, 115–125 µm wide; vesica with three large spine-like cornuti and numerous minute spine-like cornuti.

Female genitalia (Figs 44, 45). Total length 770–1000 µm. Anterior and posterior apophyses almost equal in length. Vestibulum without sclerites. Corpus bursae with very large folded part and smaller, 270 µm long, basal part; pectinations indistinctive; signa absent. Accessory sac large, rounded; ductus spermathecae with one sclerite. Abdominal apex narrowed and distally truncated.

Bionomics (Figs 46–48). Host-plant: boxleaf azara ( Azara microphylla Hook. f., Salicaceae). Larva mines in leaves in September. Leaf-mine (Figs 46–48) starts as a very slender sinuous gallery with not continuous but interrupted central line of black frass; further in, the gallery widens to a large elongated blotch with black-brown frass distributed irregularly and with very wide areas free of frass. Larval exit slit (Fig. 48) on upper side of the leaf. Adults fly from late September to November and in January.

Distribution (Figs 1). This species occurs in the southern Andes (Argentina: Chubut, Neuquen and Río Negro Provinces) at altitudes around 600– 800 m.

Etymology. The species name is derived from Latin unum (one, single) and caudatus (caudate) in reference to the gnathos with a single caudal process in the male genitalia.