Yellow light of firefly insect flying in the night forest, background of Taiwan.

Why do some insects and jellyfish glow?

Many insects and animals glow in the dark in order to lure preys and deter predators.

But guess what, fireflies aren’t the only ones in the animal kingdom that come with an enchanting display of light. Starting from jellyfish and squids to glow worms, there are others too, who have a luminescent side to them. Now the question is, what’s the secret behind their fascinating glow?

Glowing mushrooms on bark with fireflies in forest

Well, the answer is bioluminescence, a natural phenomenon that enables living organisms emit light. This happens due to a chemical reaction taking place within the cells of these organisms to help them perform certain vital functions like self-protection, attracting mates, luring preys and much more.


Fireflies, as we all know, are winged beetles blessed with the power of producing light on their own. Well, this is because they are endowed with special light producing organs in their abdomen called ‘lanterns’ (How appropriate is that!).

In these organs, a chemical reaction takes place among oxygen, calcium, a pigment named luciferin and an enzyme named luciferase. This helps them emit light. They do it primarily to lure prey and attract potential mates.

In fact, you’ll be surprised to know that fireflies can not only produce their own light but also synchronise their light emission.


Apart from firefly, jellyfish, the transparent aquatic animal with a jelly-like appearance, too has the ability to glow in the dark. In fact, jellyfish is known to emit blue or green light. But how do they do it?

Jellyfish, Beautiful Jellyfish In The Deep Sea Background

Well, research reveals that jellyfish secrete a kind of luminescent ink present in their jelly sack that allows them to distract predators and escape. And guess what? They activate this simply by touch.

South American sea nettle jelly fish swim underwater aquarium pool with pink neon light

Also, besides their own defence mechanism, jellyfish glow in the dark to attract predators who can in turn locate and feed on one another. Isn’t that smart? They also do it to warn other organisms that they have occupied a particular region for their own species, and don’t want to be disturbed.


Squid, the eight-armed marine carnivorous mollusc with a distinguished pair of tentacles, also happens to have the special characteristic of glowing in the dark. This is how they emit light:

They take the help of a specialised gland called photophore that can produce light, thanks to presence of some chemicals in it. In fact, the light produced by squid is quite bright, considering photophores are spread over large portions of their bodies.

Usually, the colours of the light are either blue or green, helping them to navigate deep underwater and attract potential preys and hide away from predators.


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