The Glimmering World of Glow-worms - with Pete Cooper
In January we hosted another successful Zoom meeting, where a large audience listened in to an inspiring talk on glow-worms by Peter Cooper, an ecologist with the Derek Gow consultancy and an active member of the glow-worm project.

So what is a glow-worm? Well, the glow-worm is not actually a worm, but a medium-sized, narrow beetle. The only such species of beetle in the UK is Lampyris noctiluca.

Photo (Jason Steel): Female glow-worm looking to attract a mate
The males look like typical beetles and can fly to find a mate, but the females have no wings and look similar to the larvae. Glow-worms are most often found as larvae, living under rocks on chalk or limestone grassland for 2 years, and feeding on slugs and snails. They then pupate and emerge as adults. Gardens, hedgerows, railway embankments, woodland rides, heathlands and cliffs are all possible habitats for Glow-worms.

Photo: Difference between male and female glow-worms
Females are famous for emitting a greeny-orange light from the last 3 segments of their abdomens at night. They climb up plant stems and glow in order to attract males, who have large, photosensitive eyes - perfect for scanning vegetation at night. The larvae can also emit light, and so can the eggs, as a warning to predators that they do not taste good! Adults are only around for a short period in June and July.

The key to the green glow is an enzyme called luciferase, which catalyses the release of energy from the compound luciferin in the form of light, causing the rear end of the females to glow like an LED. This enzyme is used in medical research, important in the development of vaccines. It also glows in the presence of ATP, the universal energy compound found in all living cells, so it could be used to look for signs of life (on other planets!).

Pete listed the reasons for declines in glow-worm populations, a familiar litany: habitat loss and fragmentation, intensive agriculture, pollution by insecticides and light, larvae killed on roads and climate change. The glow-worm project seeks to reverse this decline by captive breeding and release into suitable habitats. Breeding them is relatively straightforward: hatch eggs and grow the larvae in small plastic containers with a substrate of coconut fibre and pieces of damp cellulose cloth to maintain high humidity in the box, and feed the larvae on young snails for 2 years until they pupate into adults.

Photo: Pete's glow-worm larvae breeding containers complete with snail food

Adults need to be released into suitable sites. There must be a good mix of scrub, long rough grassland, & areas of short grass. This should not be mowed during the glowing season (June - August). Intensively grazed areas should be avoided, as well as light pollution, and glow-worms should not already be present. In August 2021, 569 larvae were released in a trial site in Hampshire, leaving 130 to continue the captive breeding programme. The success of this release will only be determined in the summer of 2023 when these larvae finally pupate. We can’t wait to find out the results!

Pete’s passion, enthusiasm and expertise shone throughout the talk, and was bombarded by questions at the end, always a good sign that the audience has been engaged and enthused. 

Dave Sage

Photo: South Gloucestershire Council turn off street lights along the Bristol to Bath cycle track in summer

Youtube video recording of the talk
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