It must be a truly magical sight to see a whole myriad of tiny, sparkling lights suddenly illuminate the night sky; appearing as if from nowhere, glowing with luminescent intensity.
If you’re lucky enough to have seen one of these beautiful displays, you will know that I’m referring to fireflies – or maybe you know them a lightning bugs? Or perhaps even glow worms? (not to be confused with the glowing larvae of a gnat down under in Australasia).
Whatever you call them, they aren’t flies, bugs or worms! They all belong to a family of beetles aptly named Lampyridae – whose numbers boast over 2,000 species throughout the world, favouring temperate and tropical climes and preferring humid conditions.
But how and why do these guys put on such an iridescent show? Well, let’s take the ‘how’ first – they have special cells in their abdomens called photocytes. These photocyte cells are richly supplied with air and are controlled by the firefly’s nervous system. The firefly can create a chemical reaction that produces bioluminescence. The colour of their light can vary, usually being green or yellow, but it can also be pale blue, orange or even red. Fireflies omit a cold light – with all the light contained being in the visible spectrum, and giving off very little heat – incredibly the most efficient light in the world!
As to the ‘why’ – it would seem that for some fireflies it’s a great way of advertising for a mate (give me a flash there baby!) Sometimes it’s the men who do the flashing (!) to attract the girls over. If a guy manages to catch a girl’s eye, then she will signal back to say she’s interested.
Whilst in other species it can be the other way around, with the girls waving their lights in the air at the guys – there are even some fireflies who don’t light up at all! (Instead using pheromones to find their chosen one).
When turning on their lights, fireflies don’t just flash on and off, they can synchronise their winking and blinking together to create ripples of lights that a Christmas display would be envious of.
As well as attracting a mate, fireflies may also use their bioluminescence to ward off predators – reminding them they have a bitter taste (although this doesn’t put off all diners – certain toads, frogs, birds and spiders love to munch on fireflies. Indeed frogs have been found to be glowing in the dark themselves due to the number of fireflies they’ve consumed!)
Fireflies also have another trick up their wings – they use their lights as a way to mesmerise their prey – which can in fact be other fireflies! The females of Photuris fireflies have learnt to mimic the rhythmic flashing of other species, which lures unsuspecting males in – these unfortunate chaps, who are merely looking for love, then find themselves becoming the main course for dinner and are consumed by these femme fatales, who use chemicals from their meal to help develop their eggs.
These fearless femme fatales have even been known to steal and eat fireflies that have been caught in spiders’ webs – just how they achieve this and get away unscathed, remains a mystery!
Despite this rather grisly consumption, many adult fireflies don’t actually eat at all, whilst others consume only nectar for some sustenance during their short lives as adults. Fireflies spend the majority of their existence as larvae living up to two years in this form, where they enthusiastically munch their way through slugs, snails and worms, before transforming into adults, where they spend a few short weeks finding a mate and reproducing before their demise.
Whilst you might think of fireflies as modestly sized critters, there is one species, the Lamprigera, whose claim to fame is being the largest firefly in the world – these girls (as it is the females that are biggest) can be the size of your palm – with two light omitting areas on their abdomens, they sure know how to light up your world!
Sadly, as with the vast majority of my nature blogs, I have to report that fireflies are under threat. This is caused by light pollution that prevents them seeing other fireflies mating displays. As with many other creatures in this world, they are also suffering from a loss of their natural habitat, from climate change and from the use of chemicals and pesticides.
Fortunately, conservation efforts are ongoing to help restore firefly habitats, protect them from chemicals and reduce light pollution.
Needless to say, we need to treasure these glowing performers, as it’s been found that chemicals contained in their photocyte cells can be used to detect diseased cells in humans (helping to treat all manner of conditions). These useful chemicals can also be used to detect bacterial growth and spoilage in foodstuffs. Believe it or not, they’re even being used to help look out for signs of life in outer space – who knew!!
So, let’s all turn off our lights in the summertime to give these iridescent artistes a real chance to truly glow in the dark.