Mazarine Blue

The Mazarine Blue Cyaniris semiargus (Fr. Azuré des anthyllides) is a small blue butterfly. The upper side of the males is violet blue with a dark brown edge and white fringe. Females are brown all over. The undersides of both sexes are beigey grey, with a few tiny black dots.

The caterpillars overwinter in the nests of ants, which take care of them. Prior to that they eat Red Clover Trifolium pratense (Fr. Trèfle des prés). The adult butterflies fly from April to October. 

The species occurs all over temperate Europe and Asia, up to 2500 metres above sea level. In France it is widely distributed but not common in the north-west. I photographed these near Lac du Gaube in the Pyrenees. They were with an Adonis Blue Polyommatus bellargus (Fr. Azuré bleu céleste) - the bright blue butterfly in the photo - sucking minerals from some unidentified poo. 

Typically they are found in damp grassland and scrub, where the host plant grows. The population appears to be stable and it is not considered to be at risk of extinction.