ONE of Britain’s best loved native butterflies could soon become extinct, Bolton’s foremost butterfly expert has warned.

Lepidopterist Mark Lightowler, who runs Butterfly World in Moss Bank Park, has observed a sharp decline in the numbers of small tortoiseshell butterflies in Bolton over the last few years.

He records the number of adults he sees in Twitchells Farm Meadows, Barrow Bridge, every year, and says he has watched the colourful insect all but disappear from Bolton’s countryside.

In 2003 Mr Lightowler recorded 68 adults during a 12 month period, but this number fell to only four in 2004.

He saw 13 in 2005, 27 in 2006, then only one in 2007.

The number finally dropped to zero last year, and Mr Lightowler says he has not seen any this year either.

He has only found two nests of larvae at the site in the last six years, whereas he would normally expect to find one in every nettle patch.

Mr Lightowler said: “It is certainly looking like a very bleak future for the species in Britain, although records from the south of England are still showing the species in good numbers.

“Maybe a few warm summers will help save this dainty little butterfly in the future.”

He added: “This data is of course from one individual site and does not represent the total population for the Bolton area, but it does show how the species can fluctuate in numbers each year.”

Mr Lightowler believes the small tortoiseshell’s decline is due to a combination of climate change and parasitic flies and wasps.

He said: “We’ve had three bad wet summers now and that really does affect the butterflies in the chrysalis stage.”

Experts are investigating why the species has declined so rapidly in Britain, and Mr Lightowler says Butterfly World is conducting vital research to help understand what has happened.

Amateurs around the country, including 65-year-old Ray Sandiford, are also researching the impact of parasitic flies by collecting samples and sending them to Oxford University.

Mr Sandiford has built a butterfly house in his back garden in Breightmet to study Red Admirals, a species which migrates to the UK.