Small blue

Cupido minimus


This is the smallest of all UK butterflies. Males may be seen feeding on common bird’s-foot-trefoil or horseshoe vetch on lowland chalk grassland. Eggs are laid on kidney vetch and caterpillars feed on the developing flowers and seeds. They are only found on chalk grassland when this plant is present as it is an essential species for their lifecycle. The population of the small blue is declining partly because colonies are isolated and at risk of extinction if their habitat is destroyed.

How to identify

Despite its name the male small blue only has a small dusting of blue near to its body, otherwise it is a brown butterfly with pale, silver-grey underwings. The female is similar but without the blue markings on the upperwings.

Where to find it

Chalk grassland in central southern England and other small colonies, mostly in eastern Scotland


When to find it

  • May
  • June

How can people help

In southern England, small 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
Small blue
Latin name
Cupido minimus
Butterflies and moths
Wingspan 20-30mm
Conservation status
A priority species for conservation efforts