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)

Subspecies

P. c. borussia (Dadd, 1908) Ural
P. c. asturiensis Sagarra, 1922 Pajares, Cantabrian
Description

Males have pale silvery-blue wings with black-and-white border (see adjacent images). Females are dark brown, also with the black-and-white borders. As with many blue butterflies, separation from similar species in the field is on the underside markings.

Biology

Note that information on this species applies to Great Britain and some details may not be consistent with the species in other parts of its range.

In the UK, this is a species favouring unimproved (and unfertilized) chalk downland. Its larval (caterpillar) foodplant is horseshoe vetch (Hippocrepis comosa). It is usually seen on the wing for about 6–8 weeks, July to September.


Male underwing

male aberration (one spot)

Female.

Egg.

source - Wikipedia