RSPB Scotland Species and Habitats Officer James Silvey tells us about the common glow worm and the survey hoping to find out more about them.

Shine little glow-worm, glimmer, glimmer

I’ve always been fascinated by glow worms. They make me think of exotic jungle locations where fire flies blink along riverbanks. However, a few weeks ago the exotic location I found myself visiting was a forest track in Stirlingshire where myself, a group of intrepid surveyors and a few million midges were looking for Scottish glow worms.

The common glow worm (Lampyris noctiluca) is not, as the name suggests a worm, but actually a beetle whose glow is used by the flightless females to attract a mate. The adult beetles are only active for a few weeks in the early summer where winged males attempt to find as many glowing females as possible. The females broadcast their presence from the top of vegetation and after mating they turn their light off and descend to the ground to lay their eggs. Once hatched the larvae has only one thing on its mind, food, and for young glow worms there are only two items on the menu, slugs and snails. The larvae are predatory, hunting their prey and tracking their slime trails. After finding their prey the larvae inject a venom into the hapless victim, paralysing it and partly digesting it into a gastropod broth that the larvae consume. After 2-3 years feasting on snails and slugs the larvae pupate and so complete the life cycle.    

female glow worm against grass
Glowing adult female

Back to the forest track in Stirlingshire and the group had counted an amazing 20 adult glow worms. This was a good number for Scotland but paled in comparison to the “hundreds” that were often reported at sites in the beginning of the 20th century. So, what’s happened? Well glow worms are likely a victim of the habitat loss and changes in land use that are affecting so many of our species but they’re also a victim of under recording. Perhaps in the 1930s people were more likely to take a late night stroll along a forest track but today few people are out in the types of quiet, undisturbed areas glow worms love and colonies may have been forgotten about or missed. Luckily there is a team of volunteers who want to reverse that trend and through the UK glow worm survey they aim to better understand the distribution and range of these fascinating little luminaries.

If you would like to join in on the survey visit www.glowworms.org.uk for more details.

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