Glow-worms go dark all over Britain

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The Independent Online
GLOW-WORMS, the summer countryside's tiny points of light, may be declining because increased road lighting is confusing the male insects when searching for the glowing females.

Alan Stewart, a research scientist at the University of Sussex, is to study the theory under laboratory conditions and in doing so may uncover some of the secrets of one of Britain's best-loved, though now least-seen, wild creatures.

Although there are few hard statistics available, anecdotal evidence strongly suggests that the pea-sized glowing lights that shine out mysteriously from hedgerows and tufts of grass on summer nights are now missing from many sites where once they were found.

A number of reasons have been put forward for their decline, from loss of habitat to increased use of insecticides, but the growth in "light pollution", from street and road lighting and the background lighting in the sky from built-up areas, has also been suggested.

The insects are strictly nocturnal and the female, with no wings, is dependent on her luminous tail to attract a flying male. It is known that glow-worms flourish best in very dark places and one theory is that more light in the sky confuses the signal.

Dr Stewart, a lecturer in the School of Biological Sciences at Sussex, has received a grant from the British Ecological Society to test it. He has already been able to simulate the female's tiny but radiant rear in a darkened test chamber in his laboratory at Brighton with LEDs - the light-emitting diodes found as the on-off indicators in most household electronic equipment.

"The males flew down to the light, crawled all over it and even tried to mate with it," Dr Stewart said, with

a certain satisfaction.

He has spent this summer's short glow worm season - from when the insects emerge in June until about now, when the successful females have mated - establishing what light wavelengths the insects respond to, and has found them attracted by a range from yellow to various shades of green.

Next year, again under laboratory conditions, he will try to establish if the responses are affected by different background lighting, such as typical street lights might provide.

His practical research difficulty is obtaining the male insects, but Sussex is perhaps better sited for that than any other British university, sitting as it does at the foot of the South Downs, which harbour fairly numerous glow worm colonies.

"We have found that if in the laboratory we use males which have already mated, they will still respond to artifical light but their ardour is somewhat diminished," he said.

This summer an attempt is being made to start a proper statistical picture of glow-worm populations by the Wildlife Trust for Berkshire, Buckinghamshire and Oxfordshire. The trust is about to complete a detailed survey at 11 of its nature reserves.

At Dancersend nature reserve in the Chiltern beechwoods between Tring and Wendover, glow-worms were still visible on Friday night - just. The warden, Mick Jones, went hunting with his daughter Polly and found one last, hopeful female, a tiny point of green light in a moonlit wildflower meadow. It was a magical sight.

"That may well be the last of the season, although we've had up to 50 on some nights," he said.

The glow-worm, Lampyris noctiluca, is a beetle and member of the firefly family. The organs in the adult female's tail produce light by oxidising a compound called luciferin which is then reflected by minute crystals. On a dark night it can be seen 50 yards away.

Its beaming behind is not its only remarkable trait, however. The larvae spend two years feeding on snails, into which they inject a paralysing fluid. "Then they suck up the contents of the snail through their mandibles," said Robin Scagell, one of Britain's leading glow-worm experts. "Once one's started gobbling, the rest of the gang go in. You find 20 or so tiny larvae all wriggling inside a snail shell. They have a whale of a time in a snail."

Mr Scagell has a warning for those encountering the tiny lights on a warm summer's night.

"As soon as they're mated, the female starts to climb back into her daytime hiding place and puts her light out. So if you see a glow worm glowing, it's a virgin female," he said.

"There's always the risk that people will see one and take it home and think it will produce lots of baby glow worms for next year - but of course it won't."

What Makes

Them Shine?

A GLOW-WORM is far more efficient at generating light than a human. It even involves recycling.

In an example of bioluminescence - light production by living things - these tiny animals start with a chemical called luciferin, a waste by- product of their own chemistry. This is then combined in the cell with the enzyme luciferase, and molecules of oxygen and ATP, the molecule that is the cell's engine.

Together they undergo a series of reactions which lead to energy being given up and emitted from the glow-worm's abdomen as photons of greenish light.

The process is amazingly efficient: compared to a light bulb, which only turns about 10 per cent of the incoming energy into light, this natural process is roughly 95 per cent efficient.

Charles Arthur

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