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Male, Switzerland, July 2011



Male, Switzerland, July 2011

Male, Pyrenees, July 2005 (behind it are a small skipper and a Verity's mountain argus)

Same male. In this and the shot below the blue with it is an Eros blue.

Note the bold white streak reaching almost the length of the hindwing.

Sadly, this silvery argus was crushed by one of the cars that regularly pass along its mountain track.

Male, Val d'Aran, July 2001 (video frame)



Distribution

This species is not supposed to be rare in the Alps but I come across it rather rarely and have yet to find a female. I have also found it regularly in the Val d'Aran in the Spanish Pyrenees, but at just one location there. It would seem, therefore, to be a local species. Like many high mountain species it has a disjunctive distribution, flying also in Scandinavia but nowhere between Scandinavia and the Alps. This is a consequence of retreating simultaneously upwards and northwards at the end of the last Ice Age.

Both sexes are easy to identify given a good view of the underside. This sports a white ray from the base, through the bottom of the cell, to the submarginal markings. The white ray in the geranium argus begins at the end of the cell. The male upperside is a dull, silvery or turquoise blue with broad, dark margins. In the Pyrenees the margins seem to be wider than in the Alps. The female is dark above, with no blue and no orange submarginal lunules.

Like the geranium argus, this species feeds chiefly on cranesbills - the wood cranesbill, Geranium sylvaticum in Switzerland. It inhabits grassy places and flowery meadows where this grows. It hibernates as a small caterpillar but does not fly until relatively late in the year, from July into August or September.