Far out in the Channel the lights of ships at anchor flickered as the lighthouse at Anvil Point sent out its steadier beam. Late, a crescent moon shone a coppery orange.
But, undoubtedly, the most extraordinary source of light seen was the bright green glow of the glow worms inhabiting the herbaceous grassland on the cliffs and quarries in this hidden corner of southern Britain.
“It’s a wonderful sight,” said Ben Cooke, the National Trust ranger for Purbeck Dorsetwhose work includes monitoring the glowworms and caring for their habitat.
“Seeing glowworms should be on everyone’s bucket list. There is nothing else like it in this country. The first time you see one, it’s such a ‘wow’ moment.
“If you start 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 some light. But when you actually see the glow, you can’t mistake it for anything else. It’s like an LED light, really penetrating.”
The National Trust runs a project in Purbeck involving volunteer spotters who count the number of glowworms. It is working to provide the ideal conditions for them to thrive and may look at introducing more into the area.
Cooke took the Guardian on a glowworm walk this week. Near Seacombe Cliff, two females glowed brightly to attract passing males. A little further along the path, Cooke set up a “step” – a bicycle light under a plastic bin – to attract other males. Within a few minutes, 14 appeared. “A record for me,” he said. The males, which fly while searching for females, do not emit the same bright green light.
Many writers have waxed lyrical about glowworms, not least the Dorset author 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 of 13 glowworms.
Hardy wrote: “It happened to be that season of the year at which glow-worms put forth their greatest brilliancy, and the light they gave was more than sufficient for the purpose.”
Cooke isn’t sure it would have really worked. “It might be a bit far-fetched that they could be playing a game with glowworms, but it’s a remarkable light.”
He said the “messier” way of farming in Hardy’s day offered better conditions for glowworms. On these cliffs near the village of Worth Matravers, the idea is to leave the scaly cover uncut and let the hawthorn, elder, nettles, sea root and old man’s beard run. Wild marjoram, thyme and basil also grow here. “There’s a lot of food and cover for them in an area like this,” Cooke said.
The glowworms are just one of the animals that the conservation organization encourages in the area. Two years ago it acquired three coastal caves which is home to a wide variety of bats. On his side Weston Farm the site has plans to attract birds such as chough and red-backed shrew. But it’s the glowworms that often capture visitors’ imaginations. “They are so charismatic,” Cooke said.
Robin Scagell, who the UK Glowworm Survey for 35 years, said the count for the creatures this year was confusing. At a site in the Chilterns in Oxfordshire, which he has been visiting for three decades, he has seen “virtually none”, but 165 females were spotted at an annual count at Stockbridge Down in Hampshire, compared with 17 in 2023.
He said: “They are widespread but very localized and many people in rural areas don’t realize they can have glowworms within a short distance.
“The sight of glow-worms lighting our way along the hedges 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 wonder, like seeing a shooting star.”
