Peter Martin writes:
The Brimstone butterfly is regarded as the “harbinger of spring”, as the male is so noticeable due to its “brimstone” colouring when it flies strongly after its winter hibernation. Females are a more whitish-green and are, therefore, often mistaken for Large White butterflies.
This is a particularly good year for the Brimstone, as I have already seen them in the garden on several days. One year, I saw 14 on one day at Fleet Pond Nature Reserve.
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 to 300 eggs. After about ten 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 from mid-July onwards.
Brimstone butterflies can live ten months or more, if we include the hibernation period. They 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 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 arrived.
Picture credit here.
Visit this blog in May for information about the Orange Tip.
Peter Martin has acted as author for a booklet entitled “Blackwater Valley Butterflies” which contains photographs of all 32 species found in this area together with information about their life-cycles. Copies are available for £2.50 plus £1.00 p.p. from Blackwater Valley Countryside Partnership, Ash Lock Cottage, Government Road, Aldershot, Hants. GU11 2PS. (Cheques should be made payable to B.V.C.P.).