Common Blue (Polyommatus icarus)
Common and widespread, the male blue above, the female brown sometimes suffused with blue extending out from the body, and with an orange band at the outer edge of the wings.
Wholly brown females can be separated from the Brown Argus by two black spots close to the body on the underside of the forewing that are not present in the latter.
Images L-R: male; brown form female; blue form female; underside.
Flight Period: April - October