Return of the Large Blue butterfly

This week saw the 25th anniversary of the reintroduction of the Large Blue butterfly (Maculinea arion) to Britain after it was declared extinct in 1979. In 1983, researchers began introducing Large Blue butterflies from Sweden. In 2008, the species occupied 30% more colonises than it did in the 1950s. The research led by Professor Jeremy Thomas (University of Oxford & CEH) will be published online on 18th June by Science at the Science Express.

Understanding the ecology of the Large Blue butterfly has been critical in the success of the reintroduction. At the start of the decline it was believed that butterfly collectors were to blame. Then in the 1970s, Professor Jeremy Thomas discovered that the Large Blue was highly dependent upon a species of red ant (Myrmica sabuleti). The Large Blue caterpillars trick the red ants into believing it is a queen ant grub by secreting a fluid. The ants then take the caterpillar to their nest where the caterpillar feasts on ant grubs for ten months before emerging as a butterfly.

After determining this dependence it was then realised that due to a reduction in cattle grazing and myxomatosis infection in rabbits, the grass in the ant’s habitat had become overgrown. These overgrown hillsides had caused the soil to cool to a level below that required by the red ants. As the red ant populations dwindled so did the Large Blue butterfly populations. Unfortunately, all this work was completed too late to save native Large Blue populations. In the 1980s however, conservationists could then use scientific data produced by Thomas and colleagues to restore the ant’s habitat to allow the successful reintroduction of the Large Blue.

Professor Lord May of Oxford, recent President of The Royal Society and former Chief Scientific Adviser to the UK Government, said: “The recovery of the Large Blue butterfly is the world’s largest-scale, longest-running successful conservation project involving an insect. It illustrates perfectly how the application of sound science can be used to solve some of the apparently intractable problems that face conservationists worldwide today.”

Source of information: CEH news