Clouded Yellow

Fascinating facts about the Clouded Yellow

• The clouded yellow is known for occasional mass migrations that trigger sudden breeding bursts, a phenomenon recorded in Britain as "clouded yellow years". These migrations are part of its regular summer movement, with individuals sometimes travelling far enough to reach Scandinavia in favourable years. After arriving, the butterflies settle in open countryside and may breed locally, adding to the sudden population spikes observed.
• Historical records highlight several standout "clouded yellow years" when massive influxes occurred, specifically in 1877, 1947, 1983, 1992, 1994, 1996 and 2000. During these years the species arrives in unusually large numbers, prompting widespread breeding across the UK. The term reflects the link between these migration peaks and the subsequent breeding bursts that follow.
• A female clouded yellow can lay an extraordinary clutch of up to 600 eggs, each deposited singly on the leaf of a suitable food plant. This high fecundity enables rapid population growth when conditions are favourable. The eggs are laid one by one rather than in clusters, ensuring each has direct access to the host plant for the emerging caterpillar. Such prolific laying contributes to the species' ability to produce multiple generations in a single season.
• In good years the clouded yellow can fit three full generations into a single season, with the final adults still flying at the start of November. After the caterpillars finish their four moults they pupate for two to three weeks before emerging, allowing the cycle to repeat quickly when weather is warm. Because the pupa remains attached to a food-plant stem by a silk girdle, the butterfly can complete development without moving far.
• Around five per cent of female clouded yellows display a pale cream upperside rather than the usual gold, a variant that has been named form helice. These pale individuals are not a separate species; intermediate forms occur, showing a continuous range of colouration.

Sources

Every fact above was checked against these pages, and kept only where one of them states it.

• Wikipedia

At a glance

About the Clouded Yellow

As the warm sunlight dances across the open meadows, the clouded yellow butterfly emerges, its delicate wings a mesmerizing blur of sulphur and gold as it flits from flower to flower, sipping nectar with an insatiable hunger. With an airy lightness, it drifts on the breeze, its erratic flight a testament to its carefree nature, as if the very wind itself has taken on a life of its own. In this whimsical waltz, the clouded yellow weaves a trail of beauty, leaving in its wake a whispered promise of summer's warmth and vitality.

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