Holotype: ♂, pinned, with genitalia in glycerol in a small plastic vial. Original labels: “Slovakia, Belianske Tatry, Zadné Jatky, 1950–2010 m, 49°14.18’N; 20°13.50’E, 30.vii.2016, Zdenko Tokár leg.”, “HOLOTYPE Stigmella tatrica Tokár, Laštůvka & van Nieukerken” (red label), coll. Z. Tokár (to be deposited in the Central Slovakia Museum Banská Bystrica).

Paratypes: 14♂, 2♀, same locality and data as holotype, Gp. ZT ♂ 12873–5, 12878, 12918, ♀ 12876, ZT leg., coll. ZT & AL; 1♂, František Kuraj leg. & coll.; same locality as holotype, 2.viii.2014, 2♂, Gp. ZT 12266–7, ZT leg., coll. RMNH, DNA samples Tokar 12266, 12267; Belianske Tatry, Bujačí Vrch, 49°13.48’N; 20°15.55’E, 4.viii.2011, 2♂, Ignác Richter leg. & coll.; Západné Tatry, Červené Vrchy, Stoly-Temniak, 49°13.28’N; 19°54.19’E, 29.vii.2005, 3♂, Gp. ZT 9085, 9087, 9132, ZT leg., coll. AL, DNA samples RMNH.5012163, RMNH.5012164 (DNA extracts in RMNH); 1♂, Gp. Richter 9847, Ignác Richter leg. & coll. All paratypes with red label “PARATYPE Stigmella tatrica Tokár, Laštůvka & van Nieukerken”.

Adult, male (Fig. 1). Wingspan 4.0–5.0 mm. Head: frontal tuft black, collar with black lamellar scales. Antenna black, with 32–35 segments. Scape white. Thorax and tegula glossy black. Ground colour of forewing brown with dark golden sheen; dark violet metallic reflection around postmedial fascia and towards the forewing apex. Fascia shining silver, wider at costal margin. Fringe grey. Hindwing grey, no androconial scales. Abdomen brown to black with whitish scales on margins of segment and whitish anal tufts.

Female (Fig. 2). Wingspan 4.0–4.5 mm. Antenna shorter, with 26 segments. Forewing markings as male. Abdomen with remarkable protruding ovipositor, no anal tufts.

Male genitalia (Figs 3–5). Vinculum moderately long, anteriorly slightly bilobed. Uncus very broad, with posterior processes well separated, each bilobed. Gnathos with long and separated posterior processes. Valva rectangular with very short and blunt distal process. Transtilla broad with relatively short sublateral processes. Phallus cylindrical, slightly longer than genital capsule, vesica with long series of pointed cornuti of different sizes and three separate thorn-shaped cornuti near phallotrema.

Female genitalia (Fig. 6). Apophyses very long and strongly sclerotized, forming a conspicuous ovipositor protruding from abdomen. Posterior apophyses about 1.3 times as long as anterior apophyses. Anterior apophyses very broad, well sclerotized anteriorly. Length of corpus bursae shorter than posterior apophyses, devoid of pectinations. Accessory sac heavily folded, longer than corpus bursae.

Stigmella tatrica is somewhat similar to several other montane species in the Stigmella aurella group in forewing colour and pattern and in male genitalia. Externally it is indistinguishable from S. tormentillella (Herrich-Schäffer, 1860). Carpathian S. dryadella differs from the new species by more glossy forewings, a wider violet area before fascia and paler head and collar. In the male genitalia the new species is most similar to S. geimontani, S. stelviana and S. aeneofasciella, but it differs significantly from these externally. Unlike S. tatrica, S. tormentillella and S. dryadella have only one large cornutus in their vesica. In the female genitalia S. tatrica differs considerably from other species in the group by the long and strong apophyses, forming a protruding ovipositor.

The early stages of the new species are unknown. The adults were observed flying over low cover of high-altitude plant communities with the presence of Dryas octopetala and resting or quickly moving on leaves of that plant. Adults were collected during daylight hours between 29^th July and 4^th August (light collecting was not attempted). This likely represents a single annual generation.

(Figs 7–10). Stigmella tatrica is so far known only from the alpine zone of the Eastern and Western Tatra Mountains. In the Eastern Tatra it was found in the Belianske Tatra Mountains (Belianske Tatry), Zadné Jatky Mountain and Bujačí Vrch Mountain at an altitude of 1800–2010 m. In the Western Tatra it was taken in the Red Mountains (Červené Vrchy), Stoly Rocks at Temniak Mountain, near the Slovak-Polish border at an altitude of about 1800–1900 m.

The Belianske Tatra Mountains and the Red Mountains are both karst areas, built of limestone and dolomite with a dominance of subalpine or alpine grasslands with many different plants growing there, many of which are endemic, rare or endangered species. The vegetation at the type locality could belong to the Caricion firmae Gams association, with the following higher plant species commonly present: Carex firma Host (Cyperaceae), Dryas octopetala L. (Rosaceae), Androsace lactea L., Primula auricula L., Soldanella carpatica Vierh. (Primulaceae), Arenaria tenella Kit., Dianthus nitidus Waldst. & Kit., Silene acaulis (L.) Jacq. (Caryophyllaceae), Bartsia alpina L., Pedicularis oederi Vahl. ex Hornem., P. verticillata L. (Orobanchaceae), Bellidiastrum michelii Cass., Crepis jacquinii Tausch (Asteraceae), Bistorta vivipara (L.) Gray (Polygonaceae), Campanula cochleariifolia Lam. (Campanulaceae), Chamorchis alpina (L.) Rich. (Orchidaceae), Festuca versicolor Tausch (Poaceae), Galium anisophyllon Vill. (Rubiaceae), Pinguicula alpina L. (Lentibulariaceae), Ranunculus alpestris L. (Ranunculaceae), Saxifraga aizoides L., S. caesia L., S. paniculata Mill. (Saxifragaceae), Selaginella selaginoides (L.) P. Beauv. ex Schrank et Mart. (Selaginellaceae); the following mosses: Ctenidium molluscum (Hedw.) (Schimp.) (Hylocomiaceae), Ditrichum flexicaule (Schwaegr.) Hampe (Ditrichaceae), Tortella tortuosa (Hedw.) Limpr. (Pottiaceae); and the following lichen: Cetraria islandica (L.) Ach. (Parmeliaceae) (Šibík et al. 2004; Kliment et al. 2010).

The specific name tatrica, an adjective, is derived from the Tatra Mts, where the new species was discovered.

(Fig. 11). We obtained COI barcodes from legs of four specimens, two of which were partial barcodes. The Barcode Index Number is BOLD:ACU7181. The maximum K2P intraspecific distance for a full barcode is 1.5%. The nearest neighbour is Stigmella tormentillella at a distance between 6.2 and 7.1%. Both in Neighbour-Joining and Maximum Likelihood analyses S. tatrica groups consistently with S. dryadella, but bootstrap support is lacking.