Holly blue

Scientific name: Celastrina argiolus

Look out for the small Holly Blue in your garden or local park. It is the first blue butterfly to emerge in spring, and a second generation appears in summer. The caterpillars are fond of holly and ivy.

Species information

Statistics

Wingspan: 2.6-3.4cm

Conservation status

Common.

When to see

April to September

About

The holly blue is a small blue butterfly that emerges in early spring, from March to May, and then again at the end of the summer between July and September. This is the blue butterfly most likely to be found in gardens, as well as woodlands, parks and churchyards. It tends to fly high around bushes and trees, whereas other grassland blue butterflies fly low to the ground. The foodplants of the caterpillars are mainly Holly (for the spring generation) and Ivy (for the summer generation), although a wide range of other plants are used including spindle, bramble and gorse.

How to identify

The holly blue is a bright blue butterfly; females have black wing edges. It is smaller than the very rare large blue, and a lot larger than the tiny small blue. It is distinguished from all the other blues by the black spots on its silvery-blue underside - other blues sport orange spots.

Distribution

Found in England, Wales and Northern Ireland, but mostly absent from Scotland.

Habitats

Did you know?

Holly blue populations fluctuate enormously from year to year as they are parasitised by an ichneumon wasp which kills the larval stage. In turn, the decreased number of adults affects populations of the parasite, allowing time for holly blue populations to recover and the cycle to start again.

How people can help

To attract butterflies, such as the holly blue, into your garden, plant nectar-rich borders for them to feed along and climbing ivy and shrubs for overwintering insects.