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Clouded Yellow

Colias croceus

Not yet photographed by the community

Brilliant yellow migrant; good years bring large influxes.

Species Profile

Not formally assessed for UK Red List; widespread in Europe but irregular UK visitor with no resident population.

Lifespan: 2–6 weeks as adults in the wild
Size & Weight: Wingspan 42–50 mm
Habitat: Open, sunny grasslands, meadows, clover fields, and disturbed areas with herbaceous plants; typically found in warm, sheltered locations.
UK Distribution: Irregular migrant and visitor to southern and central England, with occasional records reaching Wales and Scotland; numbers fluctuate dramatically year to year depending on immigration from continental Europe.
Diet: Caterpillars feed on clover, lucerne, vetches, and other legumes; adults drink nectar from various flowers.
Predators: Spiders, robber flies, insectivorous birds, and small predatory insects.
Mating Season: May to October (multiple generations per year)
Breeding: Females lay eggs singly on host plants; larvae complete development in approximately 3–4 weeks; typically 2–3 broods per year in the UK, sometimes more in warm autumns.
Behaviour: Males patrol low over grassland in characteristic rapid, fluttering flight, seeking females. Highly mobile and migratory, with individuals capable of travelling considerable distances. Adults are strongly attracted to flowers and are most active in warm, sunny weather.

Did You Know?

•The Clouded Yellow is a powerful migrant, with some individuals travelling hundreds of kilometres from mainland Europe to reach the UK each year.
•Both males and females exhibit a characteristic yellow coloration, but females have two colour forms (yellow and white/pale), with the white form being more common in some populations.
•This species has an extremely rapid lifecycle, allowing multiple generations to develop within a single UK summer.
•In exceptionally warm autumns, UK populations can peak dramatically, creating 'clouded yellow years' when butterflies become very abundant; conversely, some years see virtually no records.
•The caterpillars are toxic to many predators due to the presence of cardiac glycosides from their legume host plants, which they sequester for defence.

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