Mike, Rudi and Finn Bright and Rose Revera

Female glow worm Parc Slip 16/7/13

The glow worm, Lampyris noctiluca, is not in fact a worm, but a bioluminescent beetle of the family Lampyridae. The glow-worm life cycle consists of 4 main stages (1. The Egg 2. The larva 3. The Pupa 4. The adult). The eggs are laid in July/August and hatch in the autumn. They survive as larvae for three years, feeding on slugs and snails, before pupating and emerging as adults in June/July of their third year.

Adult Glow-worms live for a short period of approximately 14 days. On a summer’s night, you may be lucky enough to see a small green light glowing in the darkness. Although the larvae and males can also glow, this is likely to be the female glow worm, which glows brightest in order to attract the flying males. Once mated the female will cease glowing and lay between 20 and 150 eggs under stones, logs or vegetation. 

This year, Rudi and Finn Bright and their dad Mike (of Rudi’s Tarka Challenge) spent six weeks studying glow worm populations in Bridgend and the Vale of Glamorgan, looking for glowing females in July at three sites; Parc Slip, Oldcastle Down in St Brides and Ogmore Down. Five visits to Parc Slip found three glowing females but the other sites were more productive, with over nine glow worms found at each.

Another way of surveying for glow worms is to look for the larvae. The larvae feed on slugs and snails and so can often be found in dark, damp areas where the prey can be found. Here at Parc Slip, we often see the larvae under our reptile refugia! We looked back at the data from the 2010-2011 refugia study that took place here at Parc Slip and found 149 records of glow worm larvae. A map of the sightings, below, shows that glow worm larvae were found in all the refugia areas, but there were fewer sightings in the drier areas of the nature reserve i.e. Met Field. This makes sense, as they are more likely to be found in wet conditions where slugs and snails can be found!

Parc Slip Glow Worm Locations

Following on from these surveys, the Friends of Parc Slip conservation group spent a Saturday in September building hibernacula for

Glow worm larvae Mike Bright

glow worm in the areas where the glowing females were sighted. We piled logs and sticks up to create a safe shelter to hopefully help larvae to survive the winter. You can see these hibernacula on the farm track near the Butterfly Ride.

We will be undertaking hedgelaying on the reserve over the next year in order to encourage growth at the base of hedges, which creates more shelter for glow worms and their prey. Keep an eye on the events list for opportunities to help out.

If you want to know more about Glow worms, have a look at this video that Rudi and Finn have prepared   

And please let us know if you’ve seen any glow worms!