Once Extinct, An Enigmatic Butterfly Returns to England

The most successful insect reintroduction in the world!

Sep 23, 2020

The Large Blue is once again fluttering across sunny meadows in the Cotswolds. This is the first time the rare butterfly has been seen in southwest England in 150 years, and ecologists are thrilled as it has been considered extinct in Britain for the past 40 years.

Its return to the hillsides of Rodborough Commons has been painstaking to achieve, yet, as written in The Guardian, this is the most successful insect reintroduction to date in the world. 

First they had to ensure the habitat was ideal. The Large Blue, as mentioned by The Butterfly Conservation, lives in a specific grassland habitat and must lay its eggs in the small buds of wild thyme. As red ants are also important in the butterfly’s life cycle, the area had to be suitable for red ant colonies.

Ponies and cows were brought in to graze the area, enabling the sun to heat the earth which the cold-blooded ants need to thrive. However, the grazers had to be removed by late June in order for the wild thyme to bloom.

In the meantime, according to The Guardian, an ecologist had brought 1,000 larvae in a campervan all the way from Sweden. After their release into the thyme blooms, scientists let nature’s magic unfold.

As it turns out, these delicate, flashy-blue butterflies are actually social parasites. After the butterfly larvae feed on wild thyme, they fall to the ground and start to exude a scent that dupes red ants into thinking they are ant larvae.

The eerie journey then begins. The ants “rescue” them and deposit the larvae deep underground in their own baby nursery. According to a study, these butterfly larvae do not only smell like ants, they sound like Queen ants and the worker ants give them the “red carpet” treatment.

Meanwhile, the larvae feast on ant grubs until the Large Blue become pupae. Their journey ends as they emerge from their cocoons and clamber from the underground ant nest where they can finally open their jewel-like wings.

It has been quite an odyssey for the ants, the butterflies, and the scientists! This summer, 750 Large Blue butterflies were spotted among the wild thyme in Gloucestershire, thrilling the ecologists and scientists behind this intricate rehabilitation project.

According to The National Trust, 22 organizations worked side-by-side for five years to make this happen.Park Ranger Richard Evans told The National Trust, “One of the greatest legacies of the re-introduction is the power of working together to reverse the decline of threatened species and the benefit the habitat improvements will have for other plants, insects, birds and bats on the commons.”   

There are hopes that the Large Blue will move north and become established in more locales. Fluttering across the English meadow, they are back from the brink and their appearance gives hope that more endangered species can soon be reintroduced.

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NICOLE NATHAN BEM, CONTRIBUTOR
Nicole is an editor, blogger and author who has recently left her urban life in order to be more connected with nature. In her spare time, she’s outdoors hiking in the forest, mountain biking or tending to her new permaculture garden.