- Name also: Scarce Tortoiseshell
- Family: Brushfooted Butterflies – Nymphalidae
- Subfamily: True Brushfoots – Nymphalinae
- Wing span: Large, 57–71 mm (2.28–2.08 in.).
- Wing upper side: Orange, leading edge of forewing with row of black and white blotches. Black blotches also in middle of forewing and leading edge of hind wing. Especially margin of hind wing with row of black-edged blue arcs. Forewing margins black.
- Wing underside: Marbled shades of brown. Base of wings darker than outer parts. Margins with thin, shiny, dark-blue band.
- Habitat: Forests with willow growing in wetlands.
- Flying time: April–early June, then mid-July–mid-August.
- Overwintering form: Adult butterfly.
- Larval foodplant: Different willows (Salix).
The yellow-legged tortoiseshell is a casual wanderer which normally is very rarely seen in Finland. Individuals that have overwintered can be found by lucky butterfly hunters in early spring. Finland represents the edge of its habitat and it is more common in years when the number of wanderers increases (like 2012 which has been an exceptional good year for the species).
Yellow-legged tortoiseshells can be separated from small tortoiseshells by their superior size, the more orangey colour of the upper surface of their wings, and the orange colour of the inner part of their hind wings. It can be differentiated from the compton tortoiseshell by the fact that it lacks a white blotch on the leading edge of its hind wings. Compared to the large tortoiseshell it has a whiter blotch on the leading edge of its forewings and the dark edge on its wings is broader. The surest marker is however the way that yellow-legged tortoiseshell’s legs are light-coloured (leg hair) while compton tortoiseshells’ legs are dark.
Males wait for females in forest clearings and margins, where they defend their territory. The females lay their eggs in clusters around the twigs of the host plant. The caterpillars colonise the host plant together.