Female Chalk Hill or Adonis Blue?

[Part timer]

I'm sure I'm not the only one who has trouble distinguishing the female Adonis Blue from the very similar Chalk Hill Blue.
By default, this one, taken at St Catherine's Hill, Winchester, this morning is a Chalk Hill, simply on the basis that they are far more numerous than Adonis at the site. It would be late in the season, but not exceptionally so.
However, the Adonis Blue is present at the site and generally flies later than the Chalk Hill Blue and is that just a hint of a blue suffusion around the body?
Anyone want to stick their neck out and tell me definitively which it is; and why? Then I can complete the iRecord with a clear conscience.

[Pete Eeles]

Hi Rupert,

I'd put this down as a Chalk Hill Blue, personally. A key diagnostic is the colour between the lunules on the hindwing and the wing edge, which are usually whitish in Chalk Hill Blue and more blue in Adonis, as shown here: https://www.ukbutterflies.co.uk/species ... rities.php

Cheers,

- Pete

[Part timer]

Thanks, Pete. That's a useful distinction I wasn't aware of. I was actually quite happy to see either this late in the season!