- Name also: Thor’s Fitillary
- Family: Brushfooted Butterflies (Four-footed Butterflies) – Nymphalidae
- Subfamily: Heliconians (Longwings) – Heliconiinae
- Wing span: Medium-sized, 36–47 mm (1.4–1.83 in.). Females larger than males.
- Wing upper side: Orange with black blotches.
- Wing underside: Forewing orange with black and yellow blotches and spots. Hind wing with yellow lateral band, inside area orange. Outer half of hind wing reddish brown and yellow. Wing margin with row of greyish blue arcs and unclear reddish brown rings on their basal side. Often with light-coloured or greyish blue pattern next to yellow lateral band.
- Habitat: Abundantly-flowered meadows and open forest land, often close to waterways.
- Flying time: Late June–mid-July.
- Overwintering form: Caterpillar.
- Larval foodplant: Violets and pansies (Viola).
- Endangerment: Near threatened, ssp. thore is protected.
A rare subspecies of Thore’s fritillary (ssp. thore) was discovered in Northern Karelia in eastern Finland in the 1960s, and it has since been protected. Ssp. borealis flies in the north and can even be quite abundant at times.
Thore’s fritillary is one of Finland’s 19 Heliconians. It can be recognized by the continuous thick stripe made by the black patterning along the margin of the upper side of the hind wings, the yellow lateral band on the underside of the hind wings, and the greyish blue patterning outside that.
Males fly around looking for females. There is no information available on how Thore’s fritillary lay their eggs.