Renowned for their bioluminescence, glow worms are fascinating species and June through July is the ideal time to witness their impressive night-time light shows.
Despite their common name they are not worms at all, they are insects, and beetles belonging to the firefly family to be precise.
The glow worm’s scientific name, Lampyris noctiluca, translates as ‘something that shines in the night’ which references the insect’s nocturnal nature.
It’s primarily the very poor-sighted females that produce the bright, eerie yellow-green glow to attract mates (males produce only a small amount of light).
Unlike males, females are flightless and will not travel more than a few metres in their short adult lives, which typically last just two to three weeks.
During that time, her only focus is to find a mate and breed. So, once darkness falls, she will climb atop a grass stem and display her beacon while waggling her tail to entice passing males.
Once the female has successfully mated, she will switch off her light and later lay up to 100 faintly glowing eggs in burrows on the ground before dying soon afterwards.
Glow worm larvae will grow for up to three years, living under rocks and hidden in grassy tussocks, before fully maturing.
As adult glow worms lack mouthparts, they do all their feeding as predatory larvae. They mainly predate snails and slugs and in gruesome fashion: they inject a poison that paralyses and dissolves their victim before the larvae drink up the soupy remains.
Favouring chalky or limestone areas, glow worms typically inhabit areas of grass or hedge where females can easily display.
At Hampshire & Isle of Wight Wildlife Trust, we carefully manage our nature reserves by cutting back small trees and brambles (known as scrub) to benefit a variety of wildlife, such as wildflowers and small birds. This also helps glow worms, as open habitats help females attract mates.
As well habitat loss, artificial lights can impact glow worms by distracting males away from the glowing females, while changes in land use may also affect populations. If land becomes too overgrown the females won’t be seen by the males, while pesticides and herbicides can cause harm too.
For the best chance to spot glow worms, head out after 10pm on a still, warm evening in June or July with a crescent moon – the insects are less likely to glow under a full moon.
Several of our nature reserves offer a good chance of seeing glow worms, including St Catherine’s Hill in Winchester, Bartley Heath in Hook, and Bouldnor Forest on the Isle of Wight.