The great Gloucestershire glow-worm hunt

"There's one," cried a voice in the dark. People stopped abruptly, leaning past each other to see the two pinpricks of cool, green light in the bushes.

They were glow-worms, elusive treasures of the English countryside, whose eerie luminescence can be seen only in secluded places for a few weeks each summer. Which is why pensioners, children and dozens more of us were on our hands and knees on a country path, in the middle of the night, looking for them.

That kind of pulling power is why the glow-worm is the latest creature to be enlisted in the public-relations battle against new roads. Protesters at Newbury have tried in vain to get work on the bypass there stopped because of a community of rare snails. Now the people of Tewkesbury, Gloucestershire, say a proposed relief road should not be built because it would run through one of England's largest glow-worm colonies.

More than 100 people packed into a tiny room at the town's library on Thursday to hear experts say why the glow-worms should be saved, and afterwards to visit the abandoned railway track where they can be seen.

More people turned up for the glow-worms than had come to hear the ecopundit Jonathon Porritt speak six months ago, when the local Friends of the Earth group was formed. Margaret Lucas, a commanding blonde in her 50s who described herself as a "housewife and businesswoman", said the response had been "overwhelming". She opened the meeting with notices about an organic-wine and cheese party and home-grown vegetables for sale.

The audience was almost entirely white, middle class and middle-aged. Some were pensioners, who talked about their first wondrous sight of the tiny lights, before the war. Superstition had it that glow-worms shining outside a house would protect the inhabitants from harm, said one.

There were also children, eager for their own initiation into the magic, who wriggled impatiently through a long illustrated talk by John Tyler, one of the world's glow-worm experts.

Glow-worms are not worms at all, explained Mr Tyler: they are insects of the same beetle family as fireflies. He described how he rears glow- worms at the nature reserve in Kent where he is warden. In the wild, eggs a millimetre long are laid in batches under stones, logs, or in other damp, dark places. Giving off a faint green glow, they take a month to hatch into larvae that look like caterpillars, a quarter of an inch long.

They grow for two years, still glowing, and feeding on slugs and snails, if they don't end up as food themselves: frogs, toads, spiders and hedgehogs are all partial to eating glow-worm larvae. After two years they metamorphose into fully-grown insects. The males now glow no longer, but the females glow brightly for a few days, from dusk till midnight, to attract the males.

After mating, the females turn off their light, crawl under a stone (shaking off any males still left holding on) and lay their eggs. Then they shrivel up, like a flattened paper bag, and die. Those who don't mate live longer, shining forlornly in the dark for days after the males have gone away. "There's probably some kind of moral to it," said Mr Tyler.

The numbers of glow-worms in Britain began to decline in the Fifties and Sixties. Experts put the blame on the destruction of their habitats by developers, and light pollution from streetlamps, which may be luring males away. Robin Scagell, another expert on glow-worms who is also Sky TV's resident astronomer, runs a database of sightings. He has recorded up to 700 sites, mainly in southern England, but only a handful of Tewkesbury's size.

Mr Scagell did not realise the importance of the site there until he first visited it a month ago. He disagrees with the environmental scientists already consulted by Gloucestershire County Council, who say it should be possible to move the glow-worms to a new site 20 miles away. Now that the season is nearly over, work on saving the glow-worms would have to wait a year.

Gloucestershire Wildlife Trust argues that the site survey carried out on behalf of the developers and the county council was inadequate; Peter Smith, a Trust worker, describes the plan to move the colony as "a cheap scheme to paper over the cracks. The bare minimum".

However, Chris Shaw, chief planning officer for Tewkesbury Borough Council, said the relief road was necessary because "some of the historic buildings in the town are falling to bits from the traffic".

There was a balance to be struck between caring for the environment and preserving Tewkesbury town centre, which had been designated a conservation area. While accepting that there was a "pretty strong" minority feeling in the town against the bypass, there had been a public inquiry in 1991. "They've had their argument and they've not been successful in persuading an inspector that this essential link road should not be built."

The Friends of the Earth group is now taking its case up with local councillors and may appeal to the local-government ombudsman.

Privately, members admit that it is difficult to imagine local people rallying around some less glamorous creature, like the dung beetle. The glow-worm is a star of the insect world, found in the works of Dryden, Tennyson and Shakespeare, who evoked their "ineffectual Fire" in Hamlet.

Roald Dahl's story James and the Giant Peach includes a glow-worm - voiced in the recently released animated film version by Miriam Margolyes - who ends up serving as the light in the torch of the Statue of Liberty.

"People feel very strongly about the more attractive animals - the panda, the tiger - and the glow-worm does fall into this category," said John Tyler. "If they didn't have a facility for glowing, then people wouldn't shed a tear over them, I guess. It's a bit unfair that the glow-worm has got the cuddle factor where a lot of others haven't, but that's life."