Geranium Argus, Juuka, Finland

I photographed this Geranium argus in Juuka, eastern Finland a couple of years ago. These Blue butterflies are often rather challenging to identify.

"The defining characteristic of eumedon is the unh white streak from the cell spot, along v5 to the post-discal spot, and sometimes beyond. The underside markings are more distinct in the female, which also usually has a deeper brown ground colour. It is usually tied closely to the larval hostplant, various species of Geranium, principally Wood Crane's-bill (Geranium sylvaticum)."

http://www.butterfliesoffrance.com/html/Aricia eumedon.htm