Butterfly populations are a very good indicator of the health of an area's ecosystem !!
Image contributed by U.K
photographer Bill Edwards.
Images 2 & 3 contributed by U.K
photographer Deborah Lovell.
They are migratory and come to the UK mostly in the summers, with their period of migration and breeding known as the “Clouded Yellow years”.
They are unable to survive winter in the UK, but may become more common, or even residents, with temperatures rising as a result of climate change.
Most species of this genus, as usual for Coliadinae, do not sequester toxins or other noxious compounds from their food plants.
They are therefore a well-loved prey item for predators.
They make up this disadvantage by being very nimble and better able to evade attacks by predators.
When the wings of the Clouded Yellow are open, the dorsal side is orange-yellow or golden having a broad margin, black in color.
The center of the forewing also has a black spot. The ventral side of the forewing has a lighter cast, mostly pale green in color and lacking the black border.
The dark spot on the dorsal side is also present in the ventral side, while the back side of its forewings possesses a white spot at the center, with a smaller dot (dark or white) right above it.
When the wings are closed they are lemon yellow with black spots at the end and a white spot in the center.
Since this butterfly, (like most other species of the Colias family) rest with their wings closed, the black margin present on the dorsal sides can hardly be seen.
In females, the black margin on thedorsal side is also teamed with yellow spots, which are missing in the males.
About 5% of the females of this species have a pale cream coloration on the dorsal side instead of the golden shade, known as form "helice" and often confused with the pale clouded yellow and Berger’s clouded yellow.