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

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Etymology

Origin of firefly

First recorded in 1650–60; fire + fly ¹

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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

The Photinus carolinus species of firefly has just a few weeks every summer to flash their bioluminescent lights and mate.

From The Wall Street Journal ● Jun. 3, 2026

There was such a discussion about how a firefly flashes — How many seconds?

From Los Angeles Times ● Mar. 27, 2025

“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

Every fallen eyelash and first firefly of summer .

From "Brown Girl Dreaming" by Jacqueline Woodson

Animals such as fireflies produce their own light through chemical reactions, while fluorescent organisms must first absorb light from their surroundings.

From Science Daily ● Oct. 28, 2026

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

Before her slot, she noticed there hadn’t been as many fireflies in her own backyard in Asheville, N.C., but she chalked that up to the dry weather and a neighbor’s landscaping work.

From The Wall Street Journal ● Jun. 3, 2026

When they were younger, we did fireworks, BBQ, a summer night alive with fireflies and bullfrogs, all that stuff.

From Salon ● May 31, 2026

Nali used a metal poker to scooch bright embers underneath the kettle, rustling up embers that floated like fireflies.

From "Healer of the Water Monster" by Brian Young

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