The Mystery of Glowing Bugs: What Causes Fireflies To Light Up?

Fireflies are amazing. Imagine you’re walking through a dark forest and all of a sudden you’re surrounded by tiny, glowing lights. They look like something right out of a fairytale, fireflies create a strange sense of magic in our world. shutterstock_413918983

What makes this phenomenon so captivating? It’s so intriguing and leaves many people in a state of pure awe. This caused us to ask the question, how exactly do these beautiful fireflies light up the darkness; what causes them to glow?

The science behind fireflies

For a very long time the question of how do fireflies glow stayed a mystery. For decades it was only theorized about back and forth as some of the key steps were still missing. But now, this age-old puzzle has finally been solved.  Bruce Branchini of the Connecticut college and collaborates from Yale, managed to replicate the chemical reaction of the fireflies in his lab.

Fireflies and other bioluminescent organisms glow thanks to a compound called Luciferin. Yet, there was still an important chemical missing in the equation. Branchini and his team discovered an extra oxygen molecule, the missing key, called superoxide.


Other organisms and even humans have built up their immune system to protect themselves from this chemical because it can cause inflammation and cell damage.

Within the firefly, a chemical reaction occurs between superoxide and Luciferin and as a result,  the insect lights up and we see a beautiful glow.

This explains how the firefly lights up but not the reason they create light in the first place. There is a special trigger needed to cause this chemical reaction. This is where a scientific story turns into a love story.

Romantic lights

Romance is the trigger and also the answer to why exactly the bugs glow. Sara Lewis wrote about this in her intriguing book Silent Sparks: The Wondrous World of Fireflies. The light they broadcast can be slightly compared to a Morse code.


The signal they project shows which gender and species they are. The males broadcast their signal over and over again until a female decides to reply. Here is where the hunt begins, communicating through the light. For fireflies, French isn’t the language of love but light is!

You will even find the females who like to tease by only replying every once in a while, something we call playing ‘hard to get’.

The light only goes off completely when both male and female consent to mate. This way the other males won’t be able to see the female anymore and the quest of this particular male is fulfilled.

How interesting is that?! Our world is filled with magic for those who have eyes to see it.

video made by: Vincent Brady


Leave a Reply

Your email address will not be published.