Common or Chapman's Blue?

[Part timer]

Hi

These 3 were all taken in the Monts d'Espinouse area of the Haut Languedoc in France in September this year. I know the Chapman's Blue is very difficult to separate from the Common, but I'd be interested in any opinions on these (or any pointers on nailed-on identification of the former)..

Thanks, Rupert

[Chris Jackson]

Hello Rupert,
Pending a more authoritative opinion, I would like to chip in with a comment or two if I may.
Regarding the 3rd photo, the brightness of the forward upperside veins reminds me of P. escheri, however September is a little late for Escher's Blue.
Also this pointer is subjective because it could depend on lighting conditions and freshness of individuals.

Regarding the 1st photo, we agree that the forward underside cell spot is missing which would tend to indicate P. thersites. What is peculiar is the hindwing upperside where we can see orange and black marginal markings which should only occur in Spring brood females - strange.

For me the 2nd photo is good for P. thersites. This is based on the absence of unf cell spot and the volume of the marginal orange spearhead markings which I find more generous with P. thersites than P. icarus.



Chris

[Padfield]

Hi Rupert and Chris. I wouldn't like to comment on the first one, as the picture doesn't show the most critical features. As Chris says, the lack of a cell spot points to thersites and this is therefore the default. I think the second one is almost certainly icarus. To start with, there is a cell spot. It's not obvious, being half-concealed behind the hindwing, but blowing up the image leaves me in little doubt it is there. Secondly, the black submarginal markings on the hindwing are not nearly so discrete as they should be in a normal male thersites. This is a very useful feature, easier to see than to describe because of its variability - but in general, the black markings in thersites are neatly surrounded by white rather than touching the orange inside. I see what Chris means about escheri for the third one but I think it is icarus. It's not thersites - male uppersides are quite easy from the forewing androconia (conspicuous in thersites).

Here are a couple of pictures to show the difference in the hindwing submarginal markings, both taken this year:


(black spots in clear white - thersites)


(black spots touching the orange - icarus - yes, this is a female, but it was the best picture I had in my 2016 set!)

I've chosen particularly clear individuals, to illustrate the difference, but it is nearly always apparent with a little experience, especially in males.

Guy

[Chris Jackson]

As you say Guy, the black marginal spots not touching the orange, is plainer to see on the male, the female is a little more ambiguous.
Thanks for this pointer.
Here is a male P. thersites from this year (Marseilles / west Var region), same individual unders and uppers - 03 September:
The black marginal spots do not touch the orange:

This is a female P. thersites from this year, same individual unders and uppers - 15 August:
The black marginal spots just about meet the orange:

Notice the fullness of the unh orange spearheads. I suppose this could be regional though.

Cheers, Chris

[Part timer]

Hi both

Thanks for your considered opinions and in particular for the pointers on identifying Chapman's, which hopefully I'll be able to put to good use in the future.

Cheers, Rupert