Montana Public Radio

Bug Bytes: How Fireflies Glow

Jun 16, 2020

If you’re lucky, it might be an annual occurrence in your backyard. For others, it may be a memory from a summer vacation. And for all the romantics out there, it’s the icing on the cake to a picture-perfect summer evening.

We’re talking about fireflies.

Fireflies, or lightning bugs, are famous for their glowing, flashing rear ends. But the questions are how and why do they have a glimmering derriere?

It’s called bioluminescence – when a light is produced by a chemical reaction inside a living organism. Fireflies’ abdomens contain a chemical called luciferin. When combined with oxygen and an enzyme called luciferase, the reaction causes their abdomens to light up. By regulating the airflow into the abdomen, a firefly can create a specific pattern of flashes.

But not to worry, bioluminescence is a “cold light” – it doesn’t produce heat. So there’s no chance our little friends will burst into flames.

An adult beetle of the family Lampyridae, more commonly known as a "firefly" or "lightning bug."
Credit Bruce Marlin / http://www.cirrusimage.com/beetle_firefly_Photuris_lucicrescens.htm

As far as why they glow? It’s mostly the guys…flashing to try and impress a potential mate. To ensure they are trying to attract their own species, each species has a particular pattern of flashes or wavelength of light. When a female sees the flash of a suitable suitor, she’ll respond with her own light.

But beware Romeo, some females can imitate the flash patterns of other firefly species…attracting a love-hungry male to become her next meal.

Some experts also think their bioluminescent behinds serve as a warning to potential predators – letting them know that fireflies have an awful, bitter taste.

No matter the reason, flashing is their specialty. And for some of us, it would simply not be summer without seeing the lightning-bug dance.

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