Very approximate distribution. Occurs as a very rare vagrant further north.
In the southern half of Europe this is the common 'pale' clouded
yellow. In much of the region - in my part of the Alps in particular -
it is indeed a very common butterfly from April or even March
throughout the year. The latest I have seen it is in December, at 1000m
(the last picture above, taken on 18th December!).
Berger's clouded yellow is very similar to the pale clouded yellow,
from which the adult cannot always be separated with certainty. In both
the wings are more rounded and appear less long and swept back, though
this can be very subjective and in any case is by no means constant.
The male is typically a brighter lemon yellow and
the orange spot on the hindwing is also brighter in Berger's.
Ecological and behavioural differences are often a better guide.
Although this species occurs as a migrant outside its home range it is
generally a more sedentary butterfly than the pale clouded yellow and
is usually to be found on calcarious sites where one of its main
foodplants, horseshoe vetch or crown vetch, grows. At such sites it is
present all year. In contrast, pale clouded yellows prefer clover
fields and are often opportunistic in their choice of breeding site,
being perfectly happy to use fields and verges that are suitable only
for a month or two.
This species hibernates as a small caterpillar, making the adult
photographed above in December all the more unusual. It had not been
awoken from hibernation but must have been a very late emerger from the