GET UP AND GLOW
And Roald was right. The common glowworm Lampyris noctiluca belongs to the same family as fireflies Lampyridae (which are really bioluminescent beetles) and it is the flightless female that does the glowing.
Glow-worms are a rare example of bioluminescence in terrestrial animals. This natural phenomenon is visible in a diverse array of wildlife, including insects, fungi and bacteria and more often seen in marine life, such as jellyfish, sponges, corals and squid. The meaning of light for many of these life forms is to lure prey or repel possible predators, but for the glow-worm it’s all about love.
After spending two years as a voracious, snail-devouring larva, followed by two weeks pupating under a log, the first adult glowworms usually emerge soon after sunset on June evenings. The females find a good vantage point, from where they will be visible to the smaller, winged males flying overhead, and turn on their lights. This display may last for two hours or more, but few carry on glowing much beyond midnight. For many, if they are fortunate enough to attract a male, it’s a one-night only performance. If unsuccessful, she will return to precisely the same place at the same time, for up to 10 nights, and try again.
Once mated, she will switch off her signal, lay between 50 and 150 eggs in a moist spot, then crawl away and die – her life’s job done.
The increasing illumination of our countryside – by streetlighting, home security lights, garden lights and cars – coupled with the all-too-common cocktail of habitat destruction, fragmentation and the use of pesticides, has created many ‘no glow’ areas and is thought to be one of the reasons for the species’ long-term decline. By attracting male glow-worms, artificial lighting could be reducing the female’s ability to do the same, with potentially disastrous consequences for an isolated population made even more vulnerable by the wingless female’s inability to colonise new areas. Despite the difficulties they face, glow worms are not protected in any way. Perhaps another reason most people say they’ve never seen a glow-worm is that we simply don’t go looking for them anymore. When was the last time you took a late evening stroll along a country lane? (Turn to our Great Days Out section ‘Roaming in the Gloaming’ on page 71 for more evening adventures to be had in the countryside.) Glow-worms are vastly unrecorded, making local surveys vitally important for monitoring existing sites. People are urged to submit any sightings to the national survey website www.glowworms.org.uk.
Once we have returned to the courtyard, Peter collects and collates our figures. The grand total is 103 glow-worms. This is about average, he declares, and fairly consistent over the nine years that he’s been running the survey.
Here, at the foot of the Mendip Hills, the glow-worm’s future seems secure. While less plentiful than they once were, glow-worms are probably not as rare as we think. They are still out there, like scattered, twinkling stars, waiting for us to find them.
“Unlike other bioluminiscent life forms, to the glow-worm, the meaning of light is all about love”
Pete Dommett