- Family: Brushfooted Butterflies (Four-footed Butterflies) – Nymphalidae
- Subfamily: Heliconians (Longwings) – Heliconiinae
- Wing span: Medium-sized, 33–42 mm (1.29–1.64 in.). Females usually larger than males.
- Wing upper side: Orange with black blotches.
- Wing underside: Forewing orange with blurred and hard-to-define black blotches and spots, tips pale yellow and rust-red. Hind wing a varying combination of rust-red and pale yellow areas and strips as well as white blotches. Hind wing margin with row of white blotches, unclear dark blotches immediately on their basal side.
- Habitat: Fell heaths close to and above tree line.
- Flying time: July.
- Overwintering form: Caterpillar (overwinters two seasons).
- Larval foodplant: In other countries informated yellow wood violet (Viola biflora) and Alpine bistort (Polygonum viviparum).
- Endangerment: Near threatened.
The mountain fritillary, which only flies among the Lapland fells, and the cranberry fritillary, which can be found all over Finland, differ from other Heliconians because of the sharp corner on the edge of their hind wings. It is easiest to see when the butterflies are at rest with their wings pressed together in such a way that the hind wings stay on top of the forewings. The mountain fritillary’s other identifying marks are: 1) margin of upper wings with discontinuous row of black triangles or spots, 2) underside of rear wing a colourful combination of rust-red, pale yellow and white, and 3) underside of forewing with pale yellow apex and brown stripe. The surest way to tell it apart from the cranberry fritillary is to look at the dark patterning on the underside of the forewings, which on the mountain fritillary is blurred and faint.
Males fly around looking for females. Females lay their eggs individually on the host plant.