Stared at a screen too long? Taken a blow to the head? Or standing in a forest of fireflies? The effect can be pretty much the same, except that for the latter, the story of how the lights got there is a lot more traumatic.

Although “glow-worm” is used for some of the wingless females, their young, or related insects that also light up, “true” fireflies are actually beetles. The flashes and colours, unique to each species, basically act as their dating profile and messages, and can be spontaneous or synchronised waves of glowing pinpoints rippling through the dark. Or, in the case of the “blue ghost”, Phausis reticulata, creepy blue spotlights with no insect apparently in sight.

Sadly, as beautiful as they may seem, adults have a fleeting lifespan of up to two months, and before that, it’s a hellish nightmare for other woodland crawlies.

Like the longhorn, fireflies spend most of their lives as larvae, but instead of snuggling inside wood, they wander the forest floor mercilessly slurping the innards of worms and snails after numbing them with venom. Predators tend to avoid them too, because even as larvae they have a glow that says “I taste revolting”. They continue their horrendous feasting for 1-2 years before emerging as the charming little lightning bugs we know and love.

Pyractomena borealis. Hat not to scale.

If the adults eat at all (see shortened lifespan above) it’s usually nectar and pollen. Oh I’m sorry, I forgot we were talking about the insect world for a moment. I meant to say that some of the adults are mass killers as well, and you can also throw cannibalism into the mix.

The female Photuris versicolor uses her light to trick males of other species into a rendez-vous before devouring them. Even the males with which she does enjoy a booty-call aren’t safe – sometimes, during the act, she will switch to hunter mode. The only sort-of protection the males have are arms either side of their insect todger (aedeagus), which they rest on the female to detect any weird movements. Well, at least the meat boosts the foul-tasting compounds inside her and the young, so the next generation of wood stars can survive.

So how and why do they light up? Well, special organs on their abdomen mix a cocktail of molecules and enzymes, including luciferin and luciferase, with oxygen, generating light with almost no heat and 100% efficiency. Can we harness this incredible ability? Yes, yes we can.

A recent study at the Massachusetts Institute of Technology found that, if we inject nanoparticles with luciferase into plants, they will glow for about 4 hours. One day they hope to use them to create low-energy lighting, and even plant “lamps” that react to surrounding light levels. How awesome is that?

It would be a great alternative for the fireflies too, because as well as pesticides, light pollution puts the kibosh on their mating displays. It would certainly be sad for the human world if they all disappeared, because when other animals surround you with dirty talk, it’s nowhere near as romantic.


Latin: Lampyridae (family)

What? A glowing beetle

Where? Warm and temperate regions worldwide

How big? 5-25 mm / 0.1-0.9 ” long

Endangered? It’s difficult to be sure as it’s mainly anecdotal, but there is concern that there are fewer and fewer of them, and popular “glowshows” in places like China result in masses of wild populations being harvested. And that’s bad news for any creature that spends more time growing up than mating.

Probable motto: I wink with my bum, but it’s a lot prettier than it sounds.

They look interesting. Do they need my help at all?

As above, concern is growing around the world, but I couldn’t find any specific campaigns as yet. In the meantime, this site provides some handy tips for helping your local lightning bugs:


Just to prove I’m not fibbing

Bittel, Jason. 2017. “Illuminating the secret language of lightning bugs“.

Editors of Encyclopaedia Britannica. No date. “Firefly“.

Fireflies“. No date. National Geographic.

Lewis, Sarah, and Owens, C.S. Avalon. 2017. “China’s endangered firelies“. Scientific American.

Morris, Ali. 2018. “MIT engineers transform plants into lights“.

Parry, Wayne. 2012. “Fireflies’ unique flashes help distinguish species“.

Featured image credit: “Fireflies flying in the forest at twilight” by diliananikolova