‘There’s nothing else like it’: Dorset glow-worm survey charms volunteers

Far out in the Channel, the lights of ships at anchor flickered while the lighthouse at Anvil Point emitted its steadier beam. Late on, a crescent moon shone a coppery orange.

But, undoubtedly, the most extraordinary light source to be seen was the vivid green gleam from the glow-worms that inhabit the herb-rich grassland on the cliffs and quarries in this tucked-away corner of southern Britain.

“It is a wonderful sight,” said Ben Cooke, the National Trust area ranger for Purbeck in Dorset, whose job includes monitoring the glow-worms and caring for their habitat.

“Seeing glow-worms should be on everyone’s bucket list. There’s nothing else like it in this country. The first time you see one, it’s such a ‘wow’ moment.

“If you start out early enough and the light gradually fades, it plays tricks on your eyes. People see a white flower and think: ‘Oh, is that one?’ Or raindrops on a leaf catch a bit of light. But when you actually see the glow, you can’t mistake if for anything else. It’s like an LED light, really piercing.”

The National Trust is running a project in Purbeck involving volunteer spotters counting the numbers of glow-worms. It is working on providing the ideal conditions for them to thrive and may look at introducing more into the area.

Cooke took the Guardian on a glow-worm walk this week. Close to Seacombe Cliff, two females were glowing brightly to attract passing males. A little further along the path, Cooke set up a “trap” – a bike light under a plastic bowl – to attract other males. Within a few minutes 14 had appeared. “A record for me,” he said. The males, which fly as they search for females, do not emit the same bright green light.

Many writers have waxed lyrical about glow-worms, not least the Dorset writer Thomas Hardy, who wrote a scene in his novel The Return of the Native in which two characters played a game of dice using the light from 13 glowworms.

Hardy wrote: “It happened to be that season of the year at which glowworms put forth their greatest brilliancy, and the light they yielded was more than ample for the purpose.”

Cooke is not sure this would have really worked. “It may be a bit far-fetched that they could play a game using glow-worms but it is a remarkable light.”

He said the “messier” way of farming in Hardy’s day provided better conditions for glow-worms. On these cliffs near the village of Worth Matravers, the idea is to leave the scrubby cover uncut and let the hawthorn, elder, nettles, sea carrot and old man’s beard run wild. Wild marjoram, thyme and basil also grow here. “There’s lots of food and cover for them in an area like this,” said Cooke.

The glow-worms are just one of the animals the conservation charity is encouraging in the area. Two years ago, it acquired three coastal caves that are home to a wide variety of bats. At its Weston Farm site it has plans to attract birds such as chough and red-backed shrike. But it is the glow-worms that often grab visitors’ imaginations. “They are so charismatic,” said Cooke.

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Robin Scagell, who has run the UK glow-worm survey for 35 years, said the count for the creatures this year was confusing. At a spot in the Chilterns in Oxfordshire, which he has been visiting for three decades, he has seen “virtually none” but there were 165 females spotted at an annual count at Stockbridge Down in Hampshire, compared with 17 in 2023.

He said: “They are widespread but very localised, and many people in rural areas don’t realise that they may have glow-worms within a short distance.

“The sight of glow-worms lighting our way along the hedgerows of a country lane at the height of summer, with all the smells of hay and flowers, is delightful and often unexpected. They are a source of amazement, like seeing a shooting star.”