Wiktionary
chalkhill blue
n. A silver-blue butterfly, ''Polyommatus coridon'', of the family Lycaenidae
Wikipedia
Chalkhill blue
The chalkhill blue (Polyommatus coridon) is a butterfly in the family Lycaenidae. It is found in the Palearctic ecozone (West Europe, South Europe, Central Europe, Asia Minor, South Ural, North-west Turan)