Reverdin's Blue - Plebejus argyrognomon

Reverdin's Blue
Plebejus argyrognomon

Male, Switzerland, June 2008

Female, Switzerland, June 2008

Male, Switzerland, June 2008

Female, Switzerland, June 2008

This lovely blue is similar to its congeners, the idas blue, silver-studded blue and zephyr blue. Of the three it is most like the idas blue in principle, with narrow wing borders in the male (separating it from silver-studded) and silver studs in the submarginal spots on the underside hindwing (separating it from the zephyr blue). However, in reality it is rather different from idas, having a deeper shade of blue and (in my very limited experience, at least) being a little larger. Most telling though, the orange spots on the underside forewing are broad, bright and continuous right up to the apex, marking a set of 'tramlines' that a coach could pass through.

The species is local and I saw my first individuals ever in June 2008 at a colony shown to me by a friend. The habitat looked unexceptional - a grassy meadow with crown vetch, the larval foodplant - but clearly there are quite specific requirements as the butterfly does not fly anywhere near me, even where the conditions look exactly the same.