Walkers are being asked to turn wildlife detectives to help a unique species.

The Green Hairstreak butterfly is the only on in Britain to have green wings, and conservation experts are turning to the outdoors public to help them spot them.

The Green Hairstreak butterfly 

The charity Butterfly Conservation and the Yorkshire Dales National Park Authority (YDNPA) have teamed up to run the survey of sightings of the distinctive insect, which this year has appeared two weeks earlier than usual. The Green Hairstreak’s caterpillar feeds on bilberry bushes, so the species is seen in large numbers on moorland where the plant grows. When it is perched it closes its wings, showing the green underside and white streaks

Walkers are being asked to fill in a survey form available at Yorkshire Dales National Park Centres or on the authority’s website . The survey also ran last year.

Butterfly Conservation spokesman Sam Ellis said: “Last year’s survey helped tremendously and we are hoping to build on that information, with the help of the public, this year.”

Ian Court, the YDNPA’s species officer, said: “We had a fantastic response from the public last year and the information people supplied helped to expand our knowledge of the distribution of the Green Hairstreak in the national park.

“The more we know, the easier it is to keep track of numbers and to ensure they are surviving here.”

You can find our more about our butterflies on the Butterfly Conservation website .