Adonis blue

Polyommatus bellargus


The Adonis blue is the rarest of the blue butterflies in the UK. It’s found on sunny, south-facing grassland which is rich in herbs. As with other grassland species ploughing and lack of grazing has resulted in a decline in populations. It also doesn’t move far so colonies can become isolated and vulnerable to extinction if their habitat is disturbed. The horseshoe vetch is used as a food plant by both caterpillars and adults. This species has two broods per year and as such adults can be seen from mid-May until the end of June and then from early August until the end of September. Ants, particularly the red ant and small black ants, tend the larvae and chrysalis in their nests, providing protection from predation.

How to identify

The males are a vivid, sky-blue or turquoise colour. There are fine black lines on the wings which extend into the white fringe. The females are generally brown, though this can vary and some may be mostly blue.

Where to find it

Chalk grassland in central southern England


When to find it

Adult butterflies may be seen from mid-May to the end of June and then from early August until the end of September.

  • May
  • June
  • July
  • August
  • September

How can people help

In southern England, adonis blues prefer chalk downland habitats - patchworks of chalk grassland, heath, scrub and ponds found on chalk hills. Areas of rare and unique wildlife, chalk grasslands, in particular, have been likened to a rainforest for the diversity of species they hold. But they are being lost at an alarming rate due to changes in land use causing the decline of grazing: it's estimated that we've lost 80% of our chalk grassland over the last 60 years. The Wildlife Trusts manage many grassland and downland nature reserves for the benefit of the rare wildlife they hold. You can help too: volunteer for your local Wildlife Trust and you could be involved in everything from scrub-cutting to stockwatching.

Species information

Common name
Adonis blue
Latin name
Polyommatus bellargus
Butterflies and moths
Wingspan 30-40mm
Conservation status
A species of conservation concern