This is a rather small yet distinctive European blue. The underside of both sexes features just 1 or 2 orange spots, the bigger of which is adorned with a small black pupil with a light blue centre. This renders it unique among its relatives. The upperside of the male is a lovely rich royal blue with very narrow black margins with fine white borders. The female is similar but the blue colouration is largely replaced by brown. It tends to exist in rather local, discrete colonies.

Distribution: Present in the Alps of SE France, N Italy, most of Switzerland and W Austria. Scattered across Germany, Czech Republic, E Netherlands, Denmark, Fennoscandia, Poland and the Baltic countries. Isolated populations exist in S Serbia, Kosovo and S North Macedonia.

Flight Period: Flies in a single generation from late June until mid-August.

Habitat: Raised bogs, heath, woodland clearings and edges over acidic soil and acidic subalpine scrub. Between 1500-2800m in the Alps and the Balkans, below 1400m elsewhere.

Foodplants: A variety of Vaccinium species, including Bilberry (Vaccinium myrtillus), Bog Bilberry (V. uliginosum) and Cranberry (Vaccinium oxycoccos). Sometimes Cross-leaved Heath (Erica tetralix) and Bog Rosemary (Andromeda polifolia).

Nectar Sources: Seldom visits flowers, but sometimes nectars on its Vaccinium foodplants. Males also take salts from damp soils.