Separation of Silver-studded and Idas Blue (1 Viewer)

Hi all,
I'm struggling to separate Silver-studded Blue Plebijus argus from Idas Blue Plebijus idas.

One diagnostic point is that Silver-studded has a tiny spur on the foreleg which Idas doesn't but I'd like to know, when not able to see this feature, how do you separate them?

Two images are attached, the two pic together have been identifed as Idas Blue but today I got another insect which unfortunately wouldn't allow me to photgraph the upperwing.

Just to add that I'm in St Petersburg, Russia.

Grateful for any comments or tips.


Cheers, Andy

Hi

A difficult question I have many pictures of male Silver Studded Blues, only one had a spur, in my opinion it can be a characteristic but not always
Down near the Med we have both species to date I have not seen a Idas Blue I understand the difference in underwing is the the black angular spots in front of the orange band are sharply pointed for the Idas Blue whilst the Silver Spotted are more rounded
I hope that helps

Steve

Many thanks Steve.


Andy