Our smallest resident butterfly is easily overlooked, partly because of its size and dusky colouring, but partly because it is often confined to small patches of sheltered grassland where its sole foodplant, Kidney Vetch, is found.

Males set up territories in sheltered positions, perching on tall grass or scrub. Once mated, the females disperse to lay eggs but both sexes may be found from late afternoon onwards in communal roosts, facing head down in long grass. The butterfly tends to live in small colonies and is declining in most areas. Found throughout Britain and Ireland but rare and localised.

Size and Family

  • Family: Blues
  • Size: Small 
  • Wing Span Range (male to female): 20-30mm

Conservation Status

  • Butterfly Conservation priority: Medium   
  • Section 41 species of principal importance under the NERC Act in England
  • Listed on Section 7 of the Environment (Wales) Act 2016
  • Northern Ireland Priority Species
  • UK BAP status: Priority species                      
  • Protected under Schedule 5 of the 1981 Wildlife and Countryside Act (for sale only)
  • Fully protected under the 1985 Northern Ireland Wildlife Order
  • European Status: Not threatened     

    Caterpillar Foodplant

    The sole foodplant is Kidney Vetch (Anthyllis vulneraria). The larvae live only in the flower heads where they feed on developing anthers and seed.



      Rare but found on sheltered, warm grassland habitats which have Kidney Vetch. Habitats include; chalk and limestone grassland, coastal grasslands and dunes and man-made habitats such as; quarries, gravel pits, road embankments and disused railways.


      • Countries: England, Scotland, Ireland and Wales
      • Mainly South-central England but can be found along some eastern Scottish coasts, the south coast of Wales and both the east and west coast of Ireland.
      • Distribution Trend Since 1970s: -44%

      Small Blue butterfly on a green leaf

      Small Blue (upperwing)

      Small Blue (upperwing) - Iain Leach

      Small Blue (upperwing)

      Small Blue (male/upperwing) - Bob Eade

      Small Blue (male/upperwing)

      Small Blue (upperwing) - Peter Withers

      Small Blue (upperwing)

      Small Blue (underwing) - Tamás Nestor

      Small Blue (underwing)

      Small Blue - Heath McDonald

      Small Blue (underwing)

      Small Blue (underwing) - Gillian Thompson

      Small Blue (underwing)

      Small Blue (male & female) - Gillian Thompson

      Small Blue (male & female) - Gillian Thompson

      Small Blue (egg) - Peter Eeles

      Small Blue (egg)