Northern Clouded Yellow
- Name also: Hecla Sulphur
- Family: Whites and Yellows – Pieridae
- Subfamily: Sulphurs – Coliadinae
- Wing span: Medium-sized, 35–45 mm (1.38–1.85 in.). Females larger than males.
- Wing upper side: Reddish yellow, tips and margins black. Forewing with black central blotch. Hind wing with clear or unclear orange blotch.
- Wing underside: Middle of forewing reddish yellow, tip and edges yellow or a dirty blackish yellow. Middle of forewing with black ring and edge with row of clear or unclear black spots. Hind wing yellowish black, edges whiter, middle with 1 or 2 wine-red-edged white rings. Reddish wing lahes stand out as a thin stripe on the wing margin if the wings are not worn out.
- Habitat: Fell tundra and sandy river banks with an abundance of flora.
- Flying time: Around mid-July.
- Overwintering form: Caterpillar.
- Larval foodplant: Arctic milkvetch (Astragalus frigidus) and possibly alpine milkvetch (A. alpinus).
- Endangerment: Vulnerable.
The northern clouded yellow is circumpolar but rare. In Finland it can be found in fells around Kilpisjärvi, the banks of River Tenonjoki around Utsjoki from midsummer at the earliest. The males fly restlessly round looking for females, which lay their eggs one by one on the leaves of the host plant.
Like its close relatives, the northern clouded yellow holds its wings against each other when it is resting, so their dark-edged, orangey red surface, which sets it apart from other northern sulphurs, is difficult to see without first catching it.