Clouded Yellow

Scientific Name - Colias croceus

Flight Period - May to late October

Overwinters as - Unable to survive our winters

Habitat - Grasslands and woodlands

Larval foodplants - Clovers, Common Bird’s-foot Trefoil

Conservation status - Low priority

Northamptonshire distribution - Migrant

Best public sites to see them - Being a migrant they can turn up anywhere. Recent years have seen good populations at Hanging Houghton, Lower Benefield, Lyveden New Bield and Sywell Country Park

Being a migrant butterfly the Clouded Yellow’s numbers can fluctuate dramatically each year. In most years we see Clouded Yellows in low numbers, but occasionally we have what is known as a “Clouded Yellow” year when they arrive en masse and sometimes even breed. These years should be seized upon when they occur as we never know when the next one will happen. They can sometimes arrive in the county as early as the spring but they are predominantly first recorded each year in mid-summer. However, the best numbers, especially if any summer visitors have bred, tend to be in the autumn. In 2022 in fields of cultivated Clover south of Lower Benefield 54 were recorded in one day which is a county record for abundance. In previous years they have also been recorded in large numbers at Grange Park (unfortunately this site has since succumbed to warehousing), Sywell Country Park and Lyveden New Bield, but such is the spontaneity of this butterfly’s migration they can turn up anywhere. As migrants, they are remarkably strong flyers and they are often very difficult to keep up with if trying to get a photograph. The females occasionally have a beautiful colour form known as the helice which is much paler than the normal yellow and when seen in flight looks almost entirely white. As we experience prolonged warmer weather in recent years Clouded Yellows can often be recorded well into October and in some years even into November. On the 10th of November in 2013 mating was even observed. Unfortunately, this butterfly cannot survive our winters so each year we rely on a new batch of migrants to reach us.

Clouded Yellow Distribution 2018 - 2022

Clouded Yellow

Clouded Yellow form helice

Clouded Yellow

Clouded Yellow form helice

A screenshot from a video to show the upperwing of the Clouded Yellow for helice

Mating Clouded Yellows photographed on the 10th of November at Grange Park in Northampton