Colias conundrum...

[David M]

I know one or two on here are fortunate enough to have experience of both Pale and Berger's Clouded Yellows flying in the same area, so my question is which one is this? The image comes from Provence in the south of France:

[John Vergo]

Hi David
In my eyes it look like an alfacariensis

john

[Roger Gibbons]

Hi David,

If you're thinking in terms of the straight margin and rather pointed apex, I would just mention that the alfacariensis wing shape is very variable. I have seen a few in Var that had the same reason to indicate hyale, but hyale almost certainly does not fly in Var.

I don't know where you saw it but hyale is suspected not to fly in the PACA region. There may be records for the region but mis-identification is very much more likely the reason.

Nice the see UKBers not letting Christmas get in the way of the important things in life.

John, many thanks for your pronoe location of a few years back - I plan to go there in late July next year.

Roger

[Padfield]

I was going to say much the same as Roger. Although there is on average a difference in wingshape between these two species, it is generally accepted that a single individual cannot be identified on this ground (in the same way that male humans are, on average, taller than females, but you can't sex a single individual of Homo sapiens on grounds of height). In the Var, there is a very strong presumption in favour of alfacariensis.

My experience in Switzerland, where both species do fly, is that ecological considerations are important. Hyale is a more mobile species and tends to be found in transient habitats like seasonal clover fields that might be grazed, harvested or ploughed up and planted with other stuff at different times of year. Alfacariensis is predominantly sedentary and associated with more permanent, chalk habitats where its foodplants grow. Male alfacariensis will nectar at clover but the attraction for this plant is much less. Both male and female hyale are very strongly drawn to clover. One of my favourite hyale spots is in rotated arable land in the Rhône Valley, near a road. When the fields are covered in clover, they abound with hyale. After they have been cut (for fodder, I guess), the butterflies move to the roadside verges, where they continue their obsession with clover. When there's no clover, there are no butterflies.

Guy

[David M]

Thanks for the analysis, guys. It wasn't me that saw them; I had the image sent to me by someone who's been on several of my trips.

I'm yet to see hyale (at least, knowingly) so I thought I'd run it by those who were familiar with both species.

All good for the memory bank!