A Glowing Report for Scotland

During the unpredictable Scottish summers, the thought of walking in the dark late at night, in remote places without the aid of a torch, is not everyone’s cup of tea. But get a glimpse of a female Lampyris noctiluca, commonly known as the common glow-worm, displaying her bioluminescence, and I guarantee you would be filled with wonder and awe and possibly not believing your own eyes.

‘Fireflies? In Scotland? Aye right!’ I can hear the resounding shouts from here. But it’s true, Scotland is home to a charismatic downright enchanting beetle that does indeed glow, well at least the female does.

 Female glow-worm larvae

The Life of a Glow-worm

Emitting a yellow/green bioluminescence from the last three abdominal segments, females light up at night to attract winged males during June and July. With his huge eyes, especially adapted to detect the females glow, he spends his night flying low scanning for females. Once a female is detected, he drops to the female and mating occurs. The final part of her short adult life is then spent depositing her fertilised eggs at soil level before passing away. Males perish too.

But let me go back to the start. Eggs laid in summer hatch around 45 days later, depending on temperature and humidity. The tiny larvae are deceiving and deceptively charming looking. However, they are in fact ferocious predators of snails and slugs. Using sharp mandibles, they nip at their prey whilst injecting a toxic substance that both paralyses its victim while liquifying its flesh. This allows the larva to lap up a tasty mollusc broth. Observing the predator/prey relationship can be likened to the spectacle of lions hunting in the Serengeti, only in slow motion, with several larvae attacking one snail at times. Sometimes the snail gets lucky and recovers from an attack, mostly it is reduced to just a shell. If you are very lucky, you may find a larva settling down inside a shell to digest its meal. And this is the life of the larvae for two or more years, going through its instars and spending winters in torpor under logs, stones or burrowed in the soil as prey becomes scarce. Larvae can glow, but in slow flashes, thought to be a protective response or perhaps as illumination for their nocturnal hunting.

In the spring of its second or third year, usually April or May, the fat little larva finds a suitable pupation spot and transforms into an adult. Females are very similar to the larval form, and the much smaller males are more beetle-like with distinctive huge eyes and a hood over them. Presumably to protect them as they fly through vegetation. Males do not noticeably glow.

Neither sex feeds as adults, so their energy stores built up in the juvenile stage is finite with only enough to take them through mating and egg production. Once darkness has reached a level where humans would not be able to detect colour, the females climb a short height up the vegetation and switch on their continuous glow (or, as I am seeing, they tend to glow at soil level). Sometimes you can see her waving her abdomen, so it appears as a slow blinking in her attempt to seduce the males. If no males find her, she turns off her glow and descends to shelter until the following night. Her energy stores allow her to repeat this process for up to 10 days. If she is fortunate, she will be found earlier, mated and able to lay her fertilised eggs, before dying of starvation. If she isn’t mated, her eggs will be expelled unfertilised, before she succumbs to starvation. A sad end for this magical creature either way.

Adult male glow-worm

Monitoring Glow-worm Populations in the UK

So, to me and my continued research into the populations of Scotland. England is fortunate in some ways. It's less remote, with a larger number of dedicated people prepared to conduct nocturnal site surveys. Because of this, we know glow-worms are declining. Factors include habitat loss, artificial lighting causing the inability of males to find females, pesticide use and potentially climate change. Glow-worms typically favour unimproved grassland or damp scrub with good prey populations, and that habitat is uncommon. Developments and intensive agriculture have unfortunately contributed to declines. Our use of artificial light in the form of street lamps, garden lighting and vehicle headlamps are another factor. There are many published papers concluding the effect that lighting is having on numbers. Gardeners using slug pellets is now widely understood to have detrimental effects on wildlife, and the glow-worm is no exception. Populations in England and Wales are becoming increasingly fragmented with the potential consequences of genetic problems.

Scotland however, is presenting challenges. This lovely country has many well recorded and viewed wildlife spectacles. Displaying female glow-worms is not one of them. They are massively unrecorded here. Why? Reasons could be numerous. For a start, very few people and even dedicated entomologists aren't aware of the species presence in Scotland. This country, although relatively small, is vast in terms of remoteness and accessibility in the dark. Lastly, England has a larger human population. Given that entomologists/invertebrate enthusiasts are not exactly thick on the ground, it stands that in proportion to its human population size, Scotland will not have a large number of people interested in terrestrial invertebrates. Plus, there are even less people willing to start surveying at 11.30 pm at night, in potentially tricky terrain without the aid of artificial light sources. There is only a handful of folk that dedicate some summer nights to counting glowing females on known sites. Records coming in are either from those people or from chance encounters.

Charlottes Journey into Glow-worm Research

Scotland could have far more glow-worm populations than what is known to date and what’s even more exciting is that Scotland is potentially a reservoir for the species. So how are they doing in Scotland? Declining? Thriving? We just don’t know.

That’s where I pick up. Fascinated by invertebrates since childhood, the world of bioluminescence and fireflies was to me, a world of magic and evolution at its finest. A career as a farmhand and shepherd meant I was lucky to witness some of Scotlands finest wildlife spectacles, golden eagles soaring, red deer stags rutting, black grouse lekking, salmon spawning, the list goes on. Lucky enough to work on marginal and hill farms with bosses that appreciated wildlife, it gave me the knowledge that the less favoured areas of Scotland are jewels of biodiversity. Something that is not present in intensive units or urban developments.
I stumbled across a glow-worm record on a site in England and I was immediately hooked. We have fireflies in the UK! Better still, I was researching online and finding some records in Scotland. Coinciding with retiring early from farming, I embarked on mature student life at SRUC (Scotland's Rural University College) studying Wildlife and Conservation Management. This was the start of me delving into glow-worm monitoring.

Over time, monitoring glow-worms has grown wings from me just grubbing about looking for them. My summers are now spent using an old van to travel around Scotland surveying. It gives me a chance to liaise with landowners/managers (being an ex-shepherd this is very handy when it comes to developing a good working relationship with the primary land use industry), give talks and raise awareness through social media wildlife groups, in the hopes that it will encourage people to look in their local patch or join me on large site surveys.

The rest of the year is spent scouting out potential sites, researching nil returns on historical sites, i.e. land-use changes, raising funds, speaking to researchers in England or further afield and basically making a nuisance of myself in an effort to get more folk enthusiastic. I generally find that chatting away to farmers, foresters, gamekeepers and moth enthusiasts is a good source of information. After all, they are the ones most likely to be out at stupid o’clock. Many of my sites targeted for surveys have come from these conversations.

 Adult female emitting her bioluminescent glow

Why are they so important?

As I’ve already stated, the species likes to live in relatively undisturbed habitats. Unimproved grassland and scrub or at least less environmentally impacted ground is vital for many species of invertebrates. And consequently, all the other animals that rely on them for their existence, not least our own. Fireflies are generally not included in the ‘ewwww creepy crawly’ category and are viewed as the ‘sexy’ ambassadors, along with bees and butterflies. Adding to the arsenal of contenders to attract interest in the world of invertebrates is no bad thing.

Glow-worms, as with most invertebrates, are the canaries in the mine. If something isn’t right in a habitat, the invertebrates will soon let us know. So, it may follow that thriving glow-worm populations on a site indicates healthier biodiversity.

Where to see Glow-worms

The research continues this year as it will for the rest of my life. My first glowing female was a sight I will take to my grave. The almost spiritual feeling of observing this tiny creature glowing away, not giving a hoot that I was there, was the humblest moment of my life so far (and coming from a hardened ex shepherd, that’s something I am extremely grateful for).

If like me, you find the world of nocturnal creatures to be a fascinating one, take yourself off to a spot you think may have potential and walk slowly, keeping your eyes to the ground. You may get lucky and see jewels in the grass. But stay safe! Let someone know your intentions, get permission from landowners, look at the site in daylight to assess the terrain and carry a charged torch and mobile - or better still, don’t go alone. Unlit verges and disused railway lines can be a good place to start.
There are also many known glow-worm sites in England that conduct public glow-worm walks, raising much-needed funds for conservation work; this could also be applied to sites in Scotland in the future.

Future Work

The next stages of my research will include studying the adaptations Scottish populations may have in response to lower temperatures (early data suggests glowing can occur at lower temperatures than in England), plus a future population genetics study. As I am self-funded, efforts to raise money for field and research equipment continues. For example, I recently purchased a drone through crowd funding, which will be used as a habitat mapping tool, saving my poor old legs and speeding up the lonely process of searching for them.

Part of my work is also to champion industries that typically get some flak for being responsible for biodiversity losses. That is farming and commercial forestry. Mistakes have been made, but I am finding glow-worms on these sites, suggesting this type of land use on marginal ground may actually be helping the species.

Get Involved

If you would like to find out more about glow-worms in the UK I have an online event coming up that is free to attend, so please do join me and some great guests for an evening of illumination. You can view the event and book tickets here.

For anyone in the West Midlands, FSC BioLinks have a 'Glow-worm Field Recorder Day' at Knapp and Papermill in Worcester. It is a free event but must be booked in advance. Book here.

If you cannot venture out at night, you can follow along with my surveys on YouTube (I will be posting these once we start surveying in 2022).  

You can follow my journey over on Twitter and I am also in the process of creating a blog and Facebook page. But please feel free to contact me at scottishglowworms@gmail.com for any other information or if you are based in Scotland and would like to join me for surveys.

Every bit of support helps, as once we know where they are, in what abundance and which habitats they prefer, the job of protecting them can begin.

Useful Links

• Charlottes Go Fund Me
• UK Glow Worm Survey Website
• Scotish Glow-worms Twitter
• Free event ‘Scotland’s Glow-worms. An Evening of Illumination!’
• Charlottes YouTube