Quick facts

Common name: holly blue

Scientific name: Celastrina argiolus

Family: Lycaenidae

Habitat: woodland, parks and gardens

Caterpillar foodplant: holly and ivy flower buds 

Predators: birds, spiders

Origin: native

What do holly blue butterflies look like?

Caterpillars: small and green with pinkish marks.

Adults: the holly blue is a small butterfly, light silver blue in colour with black borders to the upper wing which are more defined in females. It can be distinguished from other blue butterflies by the black speckles on the underside of its wings. 

Wingspan: 30mm

Female holly blue butterfly feeding on hogweed

Credit: Ian Redding / Alamy Stock Photo

What do holly blue butterflies eat?

Caterpillars: feed on the flower buds of holly and ivy. The larvae bore into the side of the bud and eat the contents.
Adults: feed on nectar, tree sap and juice from rotting fruit and carrion.

How do holly blue butterflies breed?

Depending on temperatures and location, the holly blue can have between one and three broods in a year. Females lay small, flat white eggs on foodplants.

The hatched caterpillar goes through several moults before it leaves the foodplant to pupate close to the ground, where it turns a light mauve. Those that pupate in spring emerge after a few weeks but the later brood overwinters as pupae.

Close up of female holly blue butterfly

Credit: Ian Redding / Alamy Stock Photo

Where do holly blue butterflies live?

Holly blues can be seen in woods, parks and gardens in England, Wales and Northern Ireland, but are not frequent in Scotland. Yearly numbers fluctuate but they are increasingly common.

Did you know?

The holly blue is the national butterfly of Finland.

Signs and spotting tips

Spot them from April around holly bushes where the first brood are born and around ivy in the late spring where the second brood are born.

Holly blue butterfly in flight

Credit: Papilio / Alamy Stock Photo

Threats and conservation

The holly blue is not currently threatened, in fact numbers have increased significantly since the 1970s, with the species becoming more widespread.