firefly

American  

[fahyuhr-flahy] / ˈfaɪərˌflaɪ /

noun

• fireflies
  plural

1. any nocturnal beetle of the family Lampyridae, characterized by a soft body with a light-producing organ at the rear of the abdomen.

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firefly British  

/ ˈfaɪəˌflaɪ /

noun

1. any nocturnal beetle of the family Lampyridae , common in warm and tropical regions, having luminescent abdominal organs See also glow-worm

2. any tropical American click beetle of the genus Pyrophorus , esp P. noctiluca , that have luminescent thoracic organs

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Other Word Forms

Noun Inflected Forms

• fireflies
  plural

Etymology

Origin of firefly

First recorded in 1650–60; fire + fly ¹

Explanation

Fireflies are flying beetles that glow in the dark. If you gently catch a firefly between your palms, you can watch its light flicker on and off for a while, and then let it go. Depending on where you live, you may call fireflies "lightning bugs" or "glowworms." There are fewer of these light-emitting insects on the planet than there used to be, but you can still find places where they gather in groups at dusk, glowing and flickering like stars. Contrary to their name, fireflies aren't flies, but instead belong to a family of beetles with an amazing ability to produce a luminous light.

Example Sentences

See Examples For:

firefly fireflies

That’s harder than trying to spot a firefly right next to someone flashing their high-beams at you.

From Los Angeles Times ● Aug. 28, 2026

The number of applications for parking spots at Great Smoky Mountains National Park during the annual eight-night firefly viewing period.

From The Wall Street Journal ● Jun. 5, 2026

“It takes the light coming from the firefly and bends it and amplifies it so we can see it in glorious detail,” he told BBC News.

From BBC ● Dec. 11, 2024

Emotionally, after riding through a cavern featuring a frog-led band with a firefly chorus, all creating a rousing, sing-along take on “Dig a Little Deeper,” the mood is one of pure uplift.

From Los Angeles Times ● Jun. 11, 2024

I kissed Harry’s bent head and went out to the porch, where the others were assembling to watch for the first firefly.

From "The Evolution of Calpurnia Tate" by Jacqueline Kelly

He has also used the technology for art installations with flexible rods that, when speared into the ground, have tips that glow in the dark like fireflies on tall grass.

From Barron's ● Aug. 5, 2026

The trick is also shared by certain squid and jellyfish species, as well as insects such as fireflies and glow-worms.

From BBC ● Jun. 25, 2026

In 2012, a team of researchers investigating reports of synchronous fireflies stayed at their bed-and-breakfast in Kellettville, Pa., a small community surrounded by Allegheny National Forest.

From The Wall Street Journal ● Jun. 3, 2026

In a way, all animals make rhythms, whether in the form of fireflies flashing, birds chirping or even a tiger pacing back and forth.

From Salon ● Jun. 7, 2025

Another wave of fireflies rushed from her palms, but not nearly as many as before.

From "Beasts of Prey" by Ayana Gray