Reverdin's Blue
Plebejus argyrognomon

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Male, Switzerland, June 2013



Taking minerals on my backpack, Switzerland, June 2013



Male, Switzerland, June 2013



Male, Switzerland, July 2013



Female, Switzerland, June 2013



Female, Switzerland, July 2013



Female, Switzerland, July 2013



Male, Switzerland, July 2013

Male, Switzerland, June 2008

Female, Switzerland, June 2008

Male, Switzerland, June 2008

Male, Switzerland, June 2008

Female, Switzerland, June 2008

Plebejus argyrognomon distribution

Distribution

This lovely blue is similar to its congeners, the idas blue, silver-studded blue and the various zephyr blues. Of these, it is most like the idas blue in principle, with narrow wing borders in the male and silver studs in the submarginal spots on the underside hindwing. However, in reality it is rather different from idas, having a slightly 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. Those on the hindwings also leave enough space for an undeviating line to be drawn through them. The black spots bordering the orange internally typically have flat, rather than concave bases. The general appearance of both sexes is of a cleaner, brighter butterfly.

The species is local, especially in Switzerland, 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. The site in Switzerland where I most regularly find Reverdin's blues is very dry, unimproved grassland.

Reverdin's blue is bivoltine, flying in May-June and then again from the end of June through July. It hibernates as an egg or small larva. Like all its relatives, it has a close relationship with ants as a larva.