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I'm pretty sure that this, rather worn, specimen is a female of either Silver-studded or Idas Blue, but I'm not sure which. Taken in the Vezere valley, France, on 12th September, so probably a bit late for either. Any opinions welcome.

Thanks, Rupert

I'd err towards Silver Studded Blue, PT. It looks to have more rounded wings than Idas would normally possess, and in any case my experience of the latter is for it to have smaller underside spots than SSB, and to also have a darker ground colour.

Here's an image of the two species side by side (SSB on the left):

Thanks, David - I've seen plenty of Silver-studded, but very few Idas, so don't really have a feel for what distinguishes them from each other.