Large Blue Butterfly

Remarkable story of the Large Blue butterfly 

 

Somerset has a lot to be proud of in the way of nature conservation. One of the most remarkable stories must be that of the Large Blue butterfly which became extinct in the UK in 1979 but now thrives in the county and in particular at Green Down, our nature reserve in the Poldens, classed as the best site in the world!

In the summer of 2009, Sir David Attenborough, visited Somerset to praise the ecologists and conservationists who have ensured the survival of the large blue which came back from the dead thanks to a red ant and an enthusiastic scientist!

Britain’s leading butterfly expert Professor Jeremy Thomas, from the University of Oxford and the Natural Environment Research Council's Centre for Ecology & Hydrology discovered the way to bring back a creature which has the most astonishing life cycle of any British insect. He spent six summers between 1972 and 1977 piecing together the chain of events which was leading to the rapid demise, and ultimate extinction in 1979, of these gorgeous butterflies.

The female butterfly lays her eggs on wild thyme plants and the larva (see photo below) falls to the ground where it is found by red ants. The larva attracts the ants by secreting a sweet ‘milk’ from its honey gland and the ants take the larva back to their nest where it then eats the ants and feeds them at the same time! It hibernates over the winter and spring before waking, feeding again, turns into a pupa in June then a large blue butterfly to start the process again.

So once Prof Thomas had got the science right reintroduction began to take place with large blues from Scandinavia, first on site X in Dartmoor, and then in 1992 on Green Down.

Sir David Attenborough said: "The restoration of the Large Blue butterfly to Britain is a remarkable success story, illustrating the power of ecological research to reverse damaging environmental changes. It is, moreover, a tribute to the dedication of many practical conservationists who have skilfully recreated its specialised habitat in our countryside."

Our connection with the Large Blue started when we saved an important piece of land. Legend has it that an unknown naturalist in the 1970s saw an inspiring south facing patch of land as he travelled on the Penzance to Paddington line and tipped off the Somerset Wildlife Trust about it (then known as Somerset Trust for Nature Conservation). That patch of land between Street and Somerton is now home to hundreds upon hundreds of these precious butterflies and known as Green Down.

Back in 1986 the site was surveyed by SERC (Somerset Environmental Records Centre) which works closely with the Trust. It was found to be a fantastic piece of habitat – species-rich grassland and superb unimproved soil which had never been intensively farmed. Glorious stuff which had conservationists from the Trust rubbing their hands in glee! So we knew the importance of this piece of land but it wasn’t ours.

But in 1988, we discovered that the owners, not knowing how important the land was, had brought in the bulldozers to construct a gallop for racing horses. Staff and volunteers quickly stepped in, and with the help of grants from South Somerset District Council and Natural England, the Trust was able to buy the land either side of the gallop.

Our chief executive at the time, Roger Martin, said: “If we had not stepped in to buy it, this site could have been completely destroyed within a year.

“Rehabilitation is going to be quite a task but at least there is nowhere to go but up!”

And how right he was! Ever since then Green Down has been carefully managed by the Trust staff and volunteers and the site was in such good condition that it was recognised by Prof Thomas, and others in the field, as a potential site ripe for the re-introduction of the Large Blue butterfly.

A committee was set up to ensure careful management of the site and in 1992 large blue adults and larvae were released by the Centre for Ecology & Hydrology at Green Down from a batch in Scandinavia. And they have been doing remarkably well ever since.

The reintroduction of the Large Blue here in Somerset would simply not have happened without the research of leading scientists Professor Thomas and David Simcox from the Centre for Ecology & Hydrology.

David Simcox said: “Having worked with the Trust and their conservation staff for nearly 20 years on this project I have found them highly skilled at habitat management and excellent at working with the public and they have always delivered what they promised – in this field these are rare commodities.”

Now in 2009 Somerset Wildlife Trust continues to carefully manage Green Down using Dorset Horn Sheep and Ruby Red Devon cattle to graze the site supplied by local farmer James Stratton. The stock are on site various times throughout the year and nibble the grass and scrub to create the ideal sward height for the red ants which are food for the Large Blues and other species.

As well as being great for the Large Blue, long term monitoring by scientists at the Centre for Ecology & Hydrology has shown that Green Down also supports large numbers of plants and animals, including many that are nationally scarce such as early gentian (flora), the nightingale and even the increasingly rare brown hairstreak butterfly.

And now Green Down is acting as a donor site for further introductions as well as seeing the Large Blue spread naturally onto neighbouring sites.

The Trust employs a warden for seven weeks of the large blue flight period – paid for thanks to grant funding from the likes of SITA and Biffaward. Green Down is such a sensitive and fragile site that Somerset Wildlife Trust closes it for six weeks in June and July when the Large Blue is on the wing and laying eggs. The warden looks after the site during this time but the Trust operates a popular ticket-only open day for members of the public. The warden mainly carries out butterfly transects and assists with the open days and public enquiries highlighting the importance of this flagship species. The Large Blue is the largest and rarest of our blue butterflies, distinguished by the unmistakable row of black spots shaped like a paw print on its upper forewing.

The Large Blue remains in decline and is a globally endangered species - but we can all be proud that it is doing so well in Somerset!

Please help us to ensure it stays that way and join the Trust. You can do so as an individual or couple or for as little as £2.50 a month and family membership is also available. But the more you can pay the more we can do for wildlife. Join us online at www.somersetwildlife.org or call the membership team on 01823 652402.

 

 

 

 

Large blue butterfly eggs laid from 1992 to 2009

The peak was over 140,000 eggs with a crash to about 60,000 due to a spring drought then a wet summer.