- Family: Brushfooted Butterflies – Nymphalidae
- Subfamily: Browns – Satyrinae
- Wing span: Medium-sized, 36–46 mm (1.41–1.8 in.).
- Wing upper side: Dark brown, forewing and hind wing with red strip along edge with black spots and eyespots with white centres.
- Wing underside: Forewing dark brown. Outer part with red strip with black, white-centred eyespots. Hind wing brown, edge with row of clear or unclear eyespots. Basal side of eyespots close to centre of wing with one or two white patches. Basal part of females’ hind wing darker than outer margin area around eyespots.
- Habitat: Forests, forest margins, logging clearings and also shores.
- Flying time: Mid-July–mid-August.
- Overwintering form: First winter as egg and second as caterpillar.
- Larval foodplant: Different grasses (Poaceae) and sedges (Carex).
The Arran brown can be found anywhere in Finland: it is common in the south and casual in Lapland. Annual numbers fluctuate biennially due to the fact that the larvae need two years to develop. The species is most abundant in oddly-numbered years.
Like all the ringlets it has eyespots surrounded by a red or reddish yellow area. The Arran brown’s flying time is usually later than the Arctic or Lapland ringlet’s. These and the dewy ringlet lack the Arran brown’s continuous red strip along the underside of the forewings and hind wings. The Arctic woodland ringlet’s can be continuous, but it lacks the white blotches on the underside of the wing that are typical of the Arran brown.
Of the butterflies that can be found in Finland, several species – especially in Lapland where the summers are short and cool – overwinter twice, usually as caterpillars (sometimes the first year as an egg), but never as adults. Other species that overwinter twice are:
(1) Arctic grayling, Jutta Arctic, Norse grayling
(2) Arctic ringlet, Arctic woodland ringlet, Lapland ringlet and Dewy ringlet
(3) Alpine grizzled skipper and often also Northern grizzled skipper
(4) Dusky-winged fritillary, Polar fritillary, Mountain fritillary and Bog fritillary
(5) Lapland fritillary