Cabbage whites are turning pink

BRITAIN'S only pink butterflies are fluttering into the history books just a stone's throw from the Royal Shakespeare Theatre in Stratford-upon-Avon.

Leading entomologists are amazed that they have witnessed a metamorphosis of one of the most common butterflies in the country, the large or 'cabbage' white, into a vibrant pink hue.

Stratford Butterfly Farm has successfully bred about 20 pink specimens of the cabbage white, Pieris brassicae. It is the first confirmed case of a pink British butterfly.

John Calvert, the farm's manager, said that the pink colour appeared to be the result of a natural mutation, and a breeding programme had begun, to identify the cause. 'Within the group there is a range of different shades of pink with some of them much darker than others, and at the moment we're just trying to sort it all out.'

Britain's leading expert on cabbage white butterflies, Brian Gardiner, who retired 10 years ago from the zoology department at Cambridge University, said he was mystified by the pink mutation. In 40 years of breeding tens of thousands of cabbage whites, including those released at the Rolling Stones concert in Hyde Park in 1969, he did not manage to produce a genuine pink form.

He said: 'I once bred a blue one and an albino form and there was once an all-black form, but in all those yearsI never came across a pink one. It is most unusual.'

Mr Gardiner said there had been unsuccessful attempts in the past to produce pink butterflies artificially by exposing the insect's chrysalis to chlorine vapour or by adding dye to the food of the caterpillars. He only came close to the dream himself by dying the adults.

David Carter, the entomologist at the Natural History Museum in London who is in charge of the nation's butterfly collection, is also suprised. 'At the museum we have about half a million specimens of British butterflies and moths and we have no pinks,' he said.

Mr Gardiner said that a rare mutation, which produces the pink coloration only when a butterfly has two copies of the defective gene, was probably responsible for the Stratford pinks.

Cabbage white butterflies may never be the same again. So common-or-garden are they that they warrant only a single sentence in the Collins Field Guide of Insects of Britain and Northern Europe: 'The yellow and black caterpillar of the Large White (P. brassicae) is nearly as bad (as its destructive small white cousin) although less widely distributed.'

John Calvert said that although collectors would pay more for undamaged dead pink butterflies than for live ones, the Stratford Butterfly Farm had no intention of dealing in dead stock, on the grounds that it would upset many of its visitors. However, he still expects a healthy trade in live pink butterflies, being sold at pounds 5 a chrysalis rather than the usual 20p for normal cabbage whites.

Whatever is causing the pink coloration, it does not affect the caterpillars, which are the normal green-yellow colour. The chrysalis, however, is a deep reddish pink, rather than the usual greenish white.

Because all the pink cabbage whites at Stratford have derived from a single pair, the biggest worry at present is that further inbreeding among the group may make them vulnerable to diseases or other genetically-related problems.

'So far there has been no problem at all and we're up to quite big numbers.

Some butterflies are more prone to inbreeding problems than others,' Mr Calvert said.

(Photograph omitted)