This thread has been bugging me
Distinguishing the females of Adonis and Chalkhill Blue is pretty difficult. So I took a trip to Martin Down today and spent 3 hours looking solely for females of both species. I've come to the following conclusion:
1. Even close-up, it's sometimes difficult to see the blue scales on the female Adonis Blue, between the red hindwing markings and the white fringe.
2. The female Adonis Blue has a blue/purple sheen that is missing from the female Chalkhill Blue.
3. The condition of the individual is a real giveaway. I only found 1 female Chalkhill Blue and it was absolutely tatty. All female Adonis Blues were immaculate (I found 11 of them).
4. Adonis Blue females are a darn sight harder to find than female Chalkhill Blue. They're easily mistaken for Brown Argus, and spent more time in the shrubbery, and less on flowers, than female Chalkhill Blue.
2 pics of the same female Adonis Blue for your viewing pleasure - showing just how subtle the blue markings are!
Cheers,
- Pete