This is our smallest butterfly, its wings a blue so smokily dark that they appear sooty brown or even black, especially because the blue scales sometimes wear off. You'll be lucky to catch sight of it: although it ranges across Britain and Ireland it is scarce, localised, and getting rarer.
Larval foodplants: Kidney vetch (a bright yellow flower of downland and grassland).
Where seen: Largely but not exclusively in chalk and limestone country where kidney vetch is common. Often found in sheltered depressions or quarries at the base of a hill.
Current conservation status: Declining across most of Britain. Down 21 per cent since 1978.