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How The Large Blue Butterfly Made A Comeback

June 16, 2009

Ecologists are finally publishing decades of research that assisted them in the project that rescued the Large Blue butterfly from extinction in the United Kingdom after its re-introduction efforts.

The butterfly was officially declared extinct in Britain in 1979, but has flourished again after conservationists had them imported from Sweden in the 1980s. They are now celebrating the 25th anniversary of the butterfly’s re-introduction.

Now there are more than 30 colonies, roughly making the total number of large blues about 20,000.

Scientists say that the research suggests how science can be utilized to slow and reverse decline of threatened species.

Andrew Sugden, Deputy and International Managing Editor at Science said, “This study tells the story of a remarkable 40-year research effort that began with painstaking fieldwork, including the counting of individual butterfly eggs laid on flowers in the English countryside, and culminated with a major conservation victory. Science is delighted to be publishing this impressive body of work, and we expect that the peer-reviewed data will be an important tool for future conservation efforts.”

For decades, collectors were thought to be responsible for declining numbers of the large blue before scientists found the true cause.

The crucial discovery was made that the life cycle of the large blue depends entirely on a species of ant called Myrmica sabuleti.

Large blue caterpillars are hatched on thyme buds and then are mistaken by M. sabuleti as ant grubs. The ants carry the caterpillars to their nests, where they feed on ant grubs for 10 months before emerging as butterflies. These disguised caterpillars secrete chemicals and even make sounds that lead the red ants to believe they are fellow grubs.

Researchers found that in 1931, conservationists bought and fenced off an area in England to keep out butterfly collectors. But the fence also kept out animals that kept the grass short. Myxomatosis (a disease caused by a virus) among rabbits also let grass grow in some areas in recent years.

This resulted in soil too cool to support adequate numbers of M. sabuleti ants, which require short grass where sunlight can warm the soil.

For lack of ants to raise their young, large blue populations dwindled.

“We discovered that the butterfly was much more specialized than anyone had thought,” said Jeremy Thomas of Oxford University who headed a study with British colleagues published in the journal Science.

“To human beings the change looks like absolutely nothing. But when you are on the scale of insects it makes a huge difference to the micro-habitats where they live,” he said.

Thomas says that the re-instatement of grazing proved to be beneficial to both the butterflies and other wildlife such as the pearl-bordered fritillary butterfly, the woodlark bird and the pale heath violet flower.

The comeback of the large blue indicated that a more extensive research into habitats at risk from expanding cities or climate change was vital to conservation efforts.

Scientists wrote, “The project tackled problems typical of many temperate butterflies that were disappearing from apparently suitable sites, and provided insights for quicker, cheaper approaches.”

The large blue butterfly and its relatives were chosen for one of three big test cases for conservation in 1974.

The other two selected for test cases were Queen Alexandra’s Birdwing of Papua New Guinea, the biggest butterfly in the world with a 1 foot wingspan, and the monarch butterfly of North America that migrates by the millions to Mexico.

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