Invasion of the giant butterflies blown way off course

A mini-invasion of giant butterflies from America has crowned a remarkable season of migrant butterflies and moths flocking to Britain.

Numbers of large monarch butterflies, which migrate in millions every year from the north-eastern US and Canada to Mexico, have been blown 3,000 miles across the Atlantic to south-west England. At least half a dozen have been seen in the Scilly Isles, Devon and Cornwall, and as far east as Dorset.

The monarchs are striking insects with large orange-and-black wings - but they represent just the final examples of spectacular visitations from butterflies and moths in 2006. Substantial numbers of one of Europe's loveliest butterflies, the black-and-cream Camberwell beauty, arrived here in August, probably by flying across Europe from Poland; more than 100 were seen in East Anglia, the highest figure for many years.

Moth migrations were even more remarkable. The spectacular hummingbird hawkmoth, which originates from north Africa and is normally the subject of modest annual UK sightings, was recorded in large numbers right across the south of England, with individual sightings in the north of England and even in Scotland.

Other rare moths have had a remarkably good year in Britain. Vast numbers of the silver y moth from north Africa arrived by July, and there were more than 30 sightings of the eastern bordered straw moth from the Canaries, which before 2000 had been seen only five times in the United Kingdom.

Much of this migration may be due to climate change, according to the charity Butterfly Conservation. "Moths and butterflies are great indicators of climate change," said the chief executive, Martin Warren. "As the weather becomes hotter as a result of global warming, we expect there to be an increase in this kind of migration to the UK."

The monarchs, however, have been brought here by strong Atlantic winds rather than a warmer climate. They are long-distance flyers anyway, and their annual 2,000-mile migrations from the US and Canada to Mexico are one of the wonders of the natural world. Hundreds of millions of them gather in Mexican mountain forests to spend the winter roosting together.

The even longer journey to Britain's West Country is one they are occasionally capable of, helped by strong west winds. They are most often found in the Scilly Isles or Cornwall, but one arrived last week in the garden near Sherborne in Dorset belonging to Clive Farrell, one of Britain's best-known amateur butterfly enthusiasts. Mr Farrell was delighted. "For me, this is a one-in-fifty-year event," he said.

The insect was in "almost perfect" condition after its mammoth journey, he said, apart from a slight tear in its hindwing. Knowing it would not survive the British winter, Mr Farrell caught it and transferred it to a greenhouse, where the temperature is similar to its Mexican hibernation territory. "My ambition is to over-winter it, which would be the first time that has been done in Britain," he said.

Dr Warren of Butterfly Conservation said the monarchs were swept up by west winds as they neared the tropics. "Even so, to get here from America is a remarkable feat," he said. He believes that the hummingbird hawkmoth, which flies during the day and has delighted many people this year, is now resident and a British breeding species.