The Clouded Yellow, Colias croceus
This mass migrator from Southern Europe and North Africa can be found in Kent particularly in late summer and autumn, and could well turn up in Hadlow parish at any time. It is often a strong flyer, and it can be very difficult to get a good photo of it! It is not a resident in the UK (except perhaps very occasionally), but variable numbers arrive each year from the continent in the spring, breed and give rise to sometimes high numbers of second or even third generation adults in late summer and autumn, the individuals most commonly seen, which eventually migrate south towards Europe again.
The overall impression is of a very yellow butterfly, with shades of orange, and then, when settled you can see the subtle spotting, particularly the main white spot or spots in the middle of the under hind wing. The detail is a tawny-orange edging and dotting.
This second photo shows the more orange underside of the fore-wing, with its main black spot:
Here is a rather better shot of another individual (again at Cliffe in 2013), this time with two (unequal) white spots in the centre of the rear wing under side:
Clouded Yellows rarely settle with their upper wings visible. Therefore I have no good photos of the upper sides of the wings, but these are more brightly orange-yellow, completely black-edged in the males, and black-edged but broken up with orange-yellow splashes in the females. Here is a distant shot of a male, blurred, in flight.
Sightings of the Clouded Yellow could occur anywhere in Hadlow – but keep your eyes peeled, one could fly past you and be out of sight in a twinkling! They may also be found feeding from the flowers of the caterpillar food plants, such as trefoils or clovers.
Migration across the sea might occur literally en masse, entirely unlike Painted Ladies and Red Admirals. There are stories of apparent “Golden Hordes” arriving at the coast, mistaken on one occasion in WWII for a potential yellow poison gas cloud! They then split up into ones or twos, across the south coast and the rest of the southern half of the country. The first adults of the year arrive in the spring, and lay initially whitish eggs that soon turn orange-ish on small legumes including trefoils, lucerne and agricultural clover. The green caterpillars grow quickly, to form a green pupa, and in a “Clouded Yellow Year” a large generation of adults emerge in August. Given further good weather another really substantial generation may emerge in September/October.
In some years, such as 1983 or 2000, the Clouded Yellow can have such a good year that it can be regarded as almost common, but in many other years very few are seen. Let us hope for another “Clouded Yellow” year soon!
About 10% of the females are form helice, where the yellow is replaced by a rather ethereal greyish white.
There are two other species of “Clouded Yellows” which occasionally migrate to the UK, both much paler, and really very difficult to distinguish from each other, or indeed from the helice form of the Clouded Yellow itself.
Predators and parasites