ChalkHill Blue (Polyommatus coridon)
Formerly Lysandra coridon
Restricted to a few sites in the Mendips and the Poldens where Horseshoe Vetch grows.
Usually flying mainly in July and August, males are shiny silvery blue, quite unmistakable, but females are a little like Brown Argus and some female Common Blues but a bit larger and the orange edging on the forewing is less pronounced.
Images L-R: male; female; undeside
Flight Period: June - September