Bright, fast-flying and impossible to ignore, the clouded yellow butterfly is a striking migrant which arrives in Britain from southern Europe and North Africa each year, bringing a splash of Mediterranean colour to our summer landscapes.

Unlike resident butterflies that spend their entire lives in the UK, the clouded yellow is a seasonal visitor. Most years only small numbers reach our shores, but occasionally weather conditions combine to produce spectacular influxes, known as ‘clouded yellow years’, when the butterflies appear in unusually large numbers across southern England.

Summer is the best time to look for this remarkable traveller. Adults can arrive from May onwards and may be seen well into autumn. Hampshire's chalk grasslands are among the most likely places to spot them, where they dart low over flower-rich slopes searching for nectar and suitable places to breed.

The clouded yellow is a medium-sized butterfly with a wingspan of up to six centimetres. Its vivid yellow-orange wings are edged with a bold black border, making it one of Britain's most eye-catching species. When resting, however, it closes its wings, revealing a greenish-yellow underside marked with distinctive silvery-white spots.

Unlike some butterflies that settle frequently on flowers, clouded yellows are restless and powerful fliers. They can be surprisingly difficult to follow as they race across open grassland, often covering considerable distances in search of food and mates. Catching a glimpse of one can feel like finding a rare piece of summer sunshine on the wing.

The species relies on grasslands rich in plants such as bird's-foot trefoil and clovers, which provide food for its caterpillars. These habitats support a huge variety of wildlife, from other butterflies and moths to bees, grasshoppers and wildflowers. 

Climate change may influence the future of the clouded yellow in Britain. Because the species cannot usually survive our winters, fresh arrivals are needed each year. However, warmer conditions may increase the number reaching our shores and could even allow the butterfly to become a more regular resident in the future.