- Family: Brushfooted Butterflies (Four-footed Butterflies) – Nymphalidae
- Subfamily: Heliconians (Longwings) – Heliconiinae
- Wing span: Small(–medium-sized), 30–40 mm (1.17–1.56 in.). Females larger than males (and usually a little darker).
- Wing upper side: Orange with black blotches.
- Wing underside: Forewing orange with black blotches and spots. Basal half of hind wing with black-edged checks comprised of reddish orange and white strips. Outer half with white margin blotches and white, black-bordered spots. Basal part of margin blotches with black arrow-shaped borders. Black spot possible close to base, but might also be lacking.
- Habitat: Bogs.
- Flying time: Southern Finland early June–early July, northern Finland early July.
- Overwintering form: Caterpillar (can overwinter in the north two seasons).
- Larval foodplant: At least bog bilberry (Vaccinium uliginosum) and bog rosemary (Andromeda polifolia), apparently also lingonberry (Vaccinium oxycoccus) and possibly even Alpine bistort (Polygonum viviparum).
The bog fritillary can be found quite rarely all around Finland except the Åland Islands in bogs, as the name suggests. A good way to recognize the species is by the black-edged white spots along the edge of the underside of their hind wings. The edge of the upper side of the hind wings have continuous sharp-tipped arcs which occasionally merge with black blotches that are close by, forming a pattern like a keyhole.
Males fly restlessly around looking for females, who lay their eggs on the host plant, apparently in small bunches.