Chalkhill blue

Polyommatus coridon

About

As the common name suggests, this butterfly is found on the chalk grasslands of southern England. The males are the more conspicuous as they fly searching for the more secretive females. Populations are declining as their grassland habitat has been ploughed up or is no longer grazed by sheep nor rabbits. Grazing stops the sward from becoming overgrown. The larval foodplant is the horseshoe vetch and the adults often feed on knapweeds and scabiouses. The caterpillars of this species are always found with ants. 

How to identify

The males are silvery blue with a dark brown/black border and a white fringe on the wings. The females are brown with a white fringe to the wings and a blue dusting near the body. They look similar to a common blue female but are larger with chequered wing fringes and the underside appears darker. The orange wing spots are also less obvious in the female chalkhill blue than the common blue. They are one of the largest blue butterflies found in Britain.

Where to find it

Southern England

Habitats

When to find it

  • July
  • August
  • September
  • October

How can people help

In southern England, chalkhill 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
Chalkhill blue
Latin name
Polyommatus coridon
Category
Invertebrates
Butterflies and moths
Statistics
Wingspan up to 40mm
Conservation status
Widespread but declining population