Britain's glow worms are fading away. One of the strangest, most charming sights of the British summer - fields scattered with tiny sparks of cool, green light - has become a rarity.
The female of the glow worm, Lampyris noctiluca, shines from late May to early July until a male finds and mates with her. This season, Sussex University biologist Alan Stewart is trying to discover what kind of environment best suits the species.
That knowledge may help to preserve the dwindling British population. It is a beetle but was called a worm because the female has a long, mottled wormy-looking abdomen.
The inch-long, wingless virgin shines from two luminescent green bands and two small dots at the end of the abdomen. She crawls to the top of a blade of grass, then switches on in the deep twilight and waits.
The smaller, winged males cruise the dark skies, looking down for the glow of a female through large black eyes. They dive, copulate, and then her light, produced by a chemical reaction, goes out. A few days later, she lays her eggs and dies.
Last week, on a couple of acres of rough pasture near Glyndebourne, East Sussex, more than a dozen were glowing as twilight disappeared. The eggs hatch in August and the larvae then take two years to become sexually mature.
There is one theory that glow worms have declined because of pollution and the glare of spreading towns, which may be confusing the males.
Dr Stewart believes the keys to their misfortune are the females' fairly sedentary nature and several decades of rapid destruction of their open, grassy habitat. "They've disappeared from numerous sites and they appear to be going in only one direction - down," said Dr Stewart. Neither the female adult nor the larvae can travel far. When a patch of good glow worm habitat is destroyed, so is the indigent population. They do not like woods or thick scrub and they cannot live in arable fields. "Apart from that, they appear to be pretty catholic in their tastes," Dr Stewart said.
At night, he and an assistant, John Newington, visit six glow worm sites on East Sussex downland and record the plant species and physical conditions there. If Dr Stewart can pin down the glow worm's precise habitat requirements, that will enable its remaining sites to be managed in a way which helps the species.Reuse content