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Someone sent me this image (upperside only, I'm sorry) and I can't quite settle on what it might be (Spanish Pyrenees was the location).

The hindwing markings don't look strong enough for Oberthur's so I was wondering whether Large or Rosy Grizzled Skipper might be more likely?

I can't claim any particular expertise, but this looks quite similar to a number of photos I submitted under the "Vercors Pyrgus" thread a few down. The conclusion in those cases was either Large Grizzled alveus or Olive serratulae.

Thanks for having a go, PT. I must say those species were the ones I erred towards (along with Rosy Grizzled Skipper). If only I had an underside.....

I don't think it looks quite right for:
alveus (nominate form) - markings too heavy
serratulae - again markings too heavy for typical serratulae, although when it is heavily marked, I don't think these markings look right
onopordi - generally onorpordi markings look a little more smudgy, especially on the uph, and onopordi is generally not an altitude species (I don't know the altitude but Spanish Pyrenees suggests a degree of altitude that would rule out onopordi)
armoricanus - possible, but as David says, the uph markings would be expected to be stronger and whiter

My guess would be alveus accretus (also known as centralhispaniae). It looks right in terms of markings and the location may well be right. It seems that little is known about the exact distribution and ups markings of accretus. Try googling Pyrgus accretus, but you won't find much that is useful.

Maybe Guy will have an opportunity to venture an opinion.

Roger

My first glance at the photo made me think Oberthur's Grizzled Skipper. But looking at the Collins guide for the "centralhispaniae" variant of Large Grizzled Skipper, made me think it could well be that.

I think Rosy Grizzled Skipper can be ruled out as your photo shows the upperside to be quite dark, whereas when I've seen Rosy Grizzled Skipper, they tend to be slightly paler.

Thank you all for this. Yes, accretus would seem to tick more boxes than any other form of pyrgus and without an underside I will err towards this diagnostic.