Reverdin's Blue

Plebejus argyrognomon has a wingspan of 28–34 mm. These small butterflies present a sexual dimorphism. The upperside of the wings is violet-blue in males, with a narrow, black border and a white fringe, while in the females it is dark brown, with black bordered orange lunules at the outer edge, especially visible on the hindwings. The underside of the wings is light beige in both sexes, with several black spots surrounded by white, an orange stripe and a marginal series of black spots pupillated in silvery blue-green. Caterpillars are pale green with orange brown longitudinal stripes, up to 20 millimeters long.

This species is similar to Plebejus argus, Plebejus idas, Plebejus pylaon and Polyommatus escheri. In Plebejus argyrognomon the underside of the wings is similar to Plebejus argus and Plebejus idas, but the background color is more gray and the black spots are relatively smaller.

This species can be found in Central and Southern Europe, Caucasus, in mountains of Southern Siberia, Mongolia and Amur River. In Japan the species is found in agricultural areas.