The brimstone butterfly: identification & favoured plants

The brimstone butterfly (Gonepteryx rhamni) can be found throughout the summer but always seems more numerous in early spring.

It's easily recognisable because the brimstone one of the only yellow British butterflies, along with the clouded yellow, but the clouded-yellow is a migratory butterfly that we see on the wing in September and October. If you've spotted a yellow butterfly in spring in the UK it's a male brimstone butterfly.

It is thought that the yellow brimstone butterfly is the species that literally put the 'butter' into 'butterfly'. The sulphur-yellow colour of the male brimstone was not only the reason for its own name but also that of the whole family of 'butter-flies'.

The female brimstone (seen in the photo above) is greenish-white in colour and beautifully veined.

Attracting brimstone butterflies

If you live in the southern half of Britain, where brimstones can be found, you might be able to attract them to your garden by planting alder buckthorn (acid soils) or purging buckthorn (other soils). It is also a good idea to allow ivy to grow on some trees to provide insects with safe areas to hibernate.

Find out how to photograph butterflies

Brimstone butterfly life cycle

Egg laying time

The brimstone has a single brood each year, its eggs are laid during April or May usually on the leaf buds of alder buckthorn.

Brimstone butterfly caterpillars

The brimstone caterpillars emerge in June and begin to feed on the buckthorn. The bluish-green caterpillars mature in about a month before pupating.

Brimstone butterfly chrysalis

In late July and early August the brimstone caterpillars form chrysalides to start the metamorphosis into a butterfly. The chrysalides are camouflaged to look like a curled green leaf, and the process takes about 2 weeks.

Transformation into butterflies

Adult brimstone butterflies emerge in late August with a wingspan of up to 6cm. These butterflies will stay on the wing until September or October before finding a safe place to hibernate.

Male and female brimstones

The easily recognisable suphur-yellow of brimstone butterflies is the upper wing of the male, while his underside is more yellow-green. Female brimstone butterflies are more white or very pale green, and might get mistaken for a cabbage white butterfly.

Brimstone butterfly and hibernation

It is a commonly held belief that butterflies do not have a long lifespan because the cold winter weather usually concludes the adult stage of a butterfly's life, but some species, including the brimstone, can survive winter by hibernating in adult form.

Both male and female brimstone have a beautifully shaped wing, which closely resembles a pale yellow leaf such as we might find on ivy in the autumn. Since ivy is an evergreen, offering good protection through the winter, the brimstone often chooses to hibernate in it.

Brimstone butterfly lifespan

If the brimstone can make it through the winter then it will have lived in its adult form from July one year to May the next making it one of the world’s longest-lived species of butterfly.

Read more about British butterflies, including other hibernating species we see waking up in spring, such as the peacock butterfly and small tortoiseshell. 

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