Butterfly of month - Brimstone

Brimstone Alan Barnes Butterfly Conervation The Brimstone butterfly is regarded as the “harbinger of spring”, as the male is so noticeable due to its “brimstone” colouring as it flies strongly after its winter hibernation. Females are a more whitish-green and are, therefore, often mistaken for Large White butterflies.

They can be spotted on n warm, sunny days throughout the winter, but as the weather warms up generally at this time of year they are likely to be seen more often in your garden or flying along the banks of the River Blackwater. They feed from various sources of nectar, such as primrose, dandelion, thistle, teasel, scabious, perennial sweet pea, buddleia and even runner bean flowers.

After courtship, the female lays her eggs singly under a young leaf or on a stem of Alder Buckthorn or Purging Buckthorn. Between April and early July, a single female may lay 200-300 eggs. After about 10 days, each egg will hatch and the resulting green caterpillar rests along the mid-line of each leaf when not chewing holes in it. Due to its green camouflage, it is often easier to spot the holes than the caterpillar itself.

On reaching full size, the caterpillar pupates by suspending itself under a leaf. This too is well camouflaged, until the yellow colour of its wings show through just before the beautiful butterfly emerges. The new generation of butterflies can be seen on the wing again from mid-July onwards.

Brimstone butterflies can live 10 months or more, if we include the hibernation period. They can spend the winter in hollow trees among the fronds of ivy, where their colour blends perfectly with the leaves. Odd Commas, Peacocks, Small Tortoiseshells or even Red Admirals butterflies may be brought out of hibernation by the warm and sunny days during the mild winters that we now experience, but it is the Brimstone that really demonstrates that spring has sprung.

Peter Martin

Peter Martin is the author of Blackwater Valley Butterflies a full-colour guide about the 32 different butterfly species butterflies found in the Valley.