You would be forgiven for thinking that, as their name suggests, glow-worms are wiggly green worms, flashing their glow-up bottoms like a gummy sweet in a sweet shop. In fact, glow-worms are not even a worm at all, but a beetle! They are part of a family of over 2000 species of beetles called Lampyridae, a group commonly known as fireflies or lightning bugs.
Glow-worms at Stockwood Open Space!
Sourced from Canva
On a warm, still summer’s evening, the My Wild City team met with residents to go in search of these elusive luminescent creatures. Find out more about how we got on and how you can look for glow-worms where you live too.
“Generally, the term glow-worm is applied to species where adult females look like their larvae (known as larviform females), are wingless and emit a steady glow of light. The females' larval looks are likely why these beetles are labelled as 'worms'. Lampyris noctiluca is the glow-worm species most often seen in the UK. These nocturnal beetles, known as common glow-worms, are found across Europe and Asia.”
The bright green glow we typically associate with them is emitted by the female to attract a mate, however glow-worm pupae and even eggs have been known to fluoresce often as a sign to predators to say, “I don’t taste good!”. Their lights are bioluminescent, a chemical reaction in an organism which produces light. The individual light of one glow-worm is remarkable but easily missed unless you are specifically looking for it.
When glow-worms congregate in large numbers in suitable habitat they make breath-taking displays of light, but this is not the state of glow-worm populations today. Studies suggest glow-worms have declined by a staggering 75% since 2001 - light pollution, habitat loss and fragmentation and insecticides have all played a part, as well as climate change. The larvae feed on damp-loving snails, and increasingly hot and dry summers mean fewer prey and a greater risk of glow-worms becoming desiccated.
(C) Alex Dommett
As part of the My Wild City project with volunteers, we’ve been improving habitats for glow-worms at Stockwood Open Space Nature Reserve – a local wildlife site on the fringes of Bristol. We embarked on a night-time stroll with local residents to learn more about these fascinating creatures and how we can spot them. It was a tall order – the last time they were recorded on this site was in the early 2000’s, and the last time a local resident saw one was a decade ago! The glimmer of hope was an iNaturalist record from last Summer - a free wildlife recording app where someone had logged their sighting. Eventually, we found two glow-worms nestled into the long grass next to a path! It really is a surreal moment to be face-to-face with a ‘living light’ and one that’s not easily forgotten.
Here are our top tips on how to look for glow-worms
- Choose a still, warm night usually between June and mid-July.
- Research your local habitats - though they favour chalky or limestone areas, glow-worms have been reported in gardens, hedgerows or railway embankments, but also on cliffs, woodland rides and heathland. Although more common in the south of England, glow worms are recorded around much of the UK.
- Check the lunar cycle - a female glow-worm’s light display is entangled with the brightness of the moon, so as to not compete with the luminosity of a full moon, glow-worms are more likely to glow during crescent moons.
- Search for previous glow-worm records on sites near you using the iNaturalist app, the NBN Atlas or your local environmental records office for a rough guide of where they’ve been spotted (or not!) in the past.
- Look for gradients of vegetation that go from low lying vegetation to tall vegetation. Glow-worms are often seen near pathways or near short grass which moves into longer grass, then scrub or hedgerow. They can then move out of the cover to fluoresce, often climbing up grass stems to show off their glowing abdomen. They can also be glowing low down in the grass so don’t expect to see them from far away, scan the ground and vegetation as you move by.
- The two - or maybe even three -year gap between a mating and the subsequent appearance of an adult means you may find plenty on a site one year, yet few or none at all the next. Therefore, sites where they seem to have died out or where they have not been recorded cannot be written off based on a single night’s search, so perseverance is key!
- Get out and enjoy your local wildlife site! Whether you see a glow-worm or not experiencing nature at night is magical, you’re more likely to discover other crepuscular (dawn and dusk) and nocturnal species such as barn owls, bats, badgers and tawny owls. Look up and enjoy the moon and stars!
People taking part in the My Wild City glow-worm walk around Stockwood Open Space (C) Alex Dommett
How to help glow-worms to thrive
- Maintain glow-worm habitats. If you know where glow-worms are, let the landowner know so they can preserve the habitat for them into the future. Because female glow worms are flightless, colonies do not migrate fast, and the species has difficulties colonising new sites, particularly with increasing fragmentation of suitable habitats. It’s really important that glow-worm sites are managed sympathetically as to not disturb them or reduce their population.
- Enhance scrub patches, creating a diversity of scrub ages will help all manner of wildlife, creating grassy patches at varying lengths that lead into scrub is a prime habitat for glow worms. Leave vegetation in known glow worm spots so there are places for larvae to overwinter.
- Found some glow-worms near streetlights? Contact the local council and let them know, is it an area where they can turn off or limit the light usage? Some local authorities such as South Gloucestershire Council have been known to turn off streetlights during the glow-worm breeding season. Top work!
- Log your glow worm sightings on iRecord and iNaturalist to help inform conservation in your area.
- Become a glow-worm champion and monitor your area for glow-worms on a regular basis. Fancy doing one at Stockwood Open Space? Let us know and get support here mywildcity@avonwildlifetrust.org.uk.
- Find out more about these incredible little creatures and share the love with others – you might like to watch Pete Cooper discuss ‘The Glimmering World of Glow-worms’ with the Avon Wildlife Trust Keynsham Group.
Go forth and glow-worm, who knows what other magical creatures you might also discover!
My Wild City is made possible thanks to the National Heritage Lottery Fund.