Pale Arctic Clouded Yellow
- Name also: Booth’s Sulphur
- Latin synonym: Colias werdandi
- Family: Whites and Yellows – Pieridae
- Subfamily: Sulphurs – Coliadinae
- Wing span: Medium-sized, 35–50 mm (1.38–1.97 in.).
- Wing upper side: Greenish white, wing veins, margins and tips darker than other parts. Forewing with black central blotch.
- Wing underside: Forewing greenish white, middle with dark ring pattern, edge with dark blotches. Hind wing dirty greenish yellow, unclear wine-red ring pattern in middle. Reddish short hairs stand out as a thin stripe on the wing margin if the wings are not worn out.
- Habitat: Fell tundra with abundant flora.
- Flying time: Late June–mid-July.
- Overwintering form: Caterpillar.
- Larval foodplant: In Finland arctic milkvetch (Astragalus frigidus), outside Finland also alpine milkvetch (A. alpinus).
- Endangerment: Vulnerable.
Like its close relatives, the pale Arctic clouded yellow holds its wings against each other when it is resting, so the upper wing surface is difficult to study without catching the butterfly first. The pale Arctic clouded yellow can be differentiated from the northern clouded yellow according to the colour of the upper side of the wings and underside of the forewings, which are yellowish white in the former and orangey red in the latter. From the moorland clouded yellow the pale arctic clouded yellow differs due to the thinner black border on the upper side of its wings and the black dots that border the underside of the forewings.
In Finland the only place that the pale Arctic clouded yellow can be found is around the fells of Kilpisjärvi. Males fly restlessly around looking for females, which lay their eggs one by one on the leaves of the host plant or close by.