Brimstone butterfly The brimstone butterfly can be found throughout the summer but always seems more numerous in early spring. It is thought that the brimstone 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 (seen in the photo) is greenish-white in colour and beautifully veined.
The brimstone has a single brood each year, its eggs are laid during April or May usually on the leaf buds of alder buckthorn. The bluish-green caterpillars mature in about a month before pupating and then, a couple of weeks later, the adult butterflies emerge.
These butterflies will stay on the wing until September or October before finding a safe place to hibernate. 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.
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.
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.