The Butterfly Conservation Society is celebrating its 40th anniversary this year and the Wiltshire Branch is holding a ball to mark the occasion.

The Conservation society, which has more than 12, 000 members, was set up by a group of naturalists in 1968 and aims to halt the decline of moths and butterflies in the UK.

The Wiltshire branch was established 12 years ago with the help of a grant from the Wiltshire Times and now has 286 members.

Maurice Avent, 64, from Manor Farmhouse, Biddestone, became chairman of the Wiltshire division last November and will become the chairman for the national organisation in September.

Mr Avent used to run Avent Engineering before retiring in 2004 to concentrate on his charity work.

He told the Country Times: "On June 7th we are having a 40th anniversary ball at Manor Farmhouse in Biddestone, which will coincide with national moth night.

"At 7.30pm there will be a champagne reception followed by a four-course dinner at 8pm.

"The chief executive of the Butterfly Conservation Society, Martin Warren, will then talk about the Society's progress and give a colourful presentation highlighting butterflies and moths, before an exciting auction of donated items.

"Sir David Attenborough has given us a video of his first three big television series, Life on Earth, The Living Planet and Trials of Life forming a trilogy set, each of which is leather bound, gilt-edged in a special slip case and signed by him in readiness for the auction.

"I've been fortunate to meet him on several occasions, he is a wonderful president for our organisation and has been voted alongside Prince Charles as Britain's leading eco-warrior."

Former presenter of The Really Wild Show and TV naturalist Chris Packham is due to attend the event, as are one Lord and two Knights of the Realm.

Tickets for the function cost £90 each and can be obtained by contacting Maurice Avent at Manor Farmhouse, Biddestone, near Chippenham SN14 7DH or by ringing (01249) 713218.

The society recently had a clear-up day to try and save some of the region's endangered species.

Wiltshire conservation members and volunteers gathered at West Yatton Down, near Castle Combe last month to clear invasive shrubs threatening several species of butterfly, including the Chalkhill Blue and Adonis Blue.

Mr Avent said: "It was a very nice day. People don't realise that the down land needs a lot of work. It can become overgrown with thorn trees and other items so we have to clear the ground.

"If it became too overgrown the butterflies would become extinct.

"The Adonis Blue and the Chalkhill Blue species require down land and grass land which hasn't be affected by herbicides and pesticides or other sprays. Woodland needs to be coppiced and felled on a regular basis for the butterflies. This used to happen in most woodland before Second World War."

The Wiltshire division has helped protect the nation's rarest species, The Duke of Burgundy, which has its strongest toehold in the county.

Mr Avent said: "The Duke of Burgundy is in very fast decline but we still enjoy the biggest colonies in Britain which are mostly in the military training area on Salisbury Plain.

"The military terrain is brilliant for the species because they lay their eggs on particularly large leaves such as primrose leaves and cowslip leaves.

"The species also requires areas of open ground where it can sun itself and the odd bush where the male can court its female.

The Duke of Burgundy is no longer in the West Yatton Down valley. It was lost about 20 years ago as a result of the grazing regime set up for the Adonis and Chalk Hill Blues not suiting its very specific requirements.

"Seventy per cent of the butterfly and moth species in the UK are in decline and the other 30 per cent are either holding their own or increasing in numbers."

If you are interested in becoming a member of the Butterfly Conservation, or if you would like to find out more visit the Wiltshire branch website at www.wiltshire-butterflies.org.uk