Male, France, August 2008
Male, Switzerland, July 2009
Female, Switzerland, July 2012
Male, Switzerland, April 2014
This species is very similar to Berger's clouded yellow and it is probably impossible to be 100% certain of identity in the field (unless a laying female or a caterpillar is found). The wings are slightly more pointed at the apex than in Berger's and the colour of the male is less bright. In the hand (or looking through the wings into the sun) more dark can be seen around the wing edges in pale clouded yellow and the dark basal area of the forewing upperside is more fanshaped (rather than extending predominantly along the trailing edge). The orange spot on the upperside of the hindwing is also much brighter orange in Berger's. I am quite confident about the identity of all the insects above. The first two show the features of this species very strongly and the last two were taken at what was clearly a breeding site, with extensive clover (I saw females down among the clover, attempting to oviposit, though males were constantly bugging them).
Berger's clouded yellow is the predominant species in the Alps and on calcareous soils, where it forms relatively sedentary colonies associated with horseshoe vetch. Pale clouded yellow is more mobile and reaches further north, flying over any kind of soil and taking a variety of foodplants.