Boloria dia - Weaver's or Violet Fritillary
Supposedly common, I seem to have had difficulty seeing and achieving a good butterfly photograph of this one.
My best opportunity was in a small meadow in the Alpe-Maritimes, where two were seen roosting, and the majority of these images were taken there. It was however becoming decidedly gloomy as the sun had gone, detracting from the quality of the eventual results. You can, however, see why it sometimes is called the Violet Fritillary.