The Real Reason Some People Say Firefly and Others Say Lightning Bug

·3 min read
Photo credit: tomosang - Getty Images
Photo credit: tomosang - Getty Images

When you see a flashing insect in your backyard, do you call it a firefly or a lightning bug? And have you ever wondered if those names refer to two different insects?

Despite their unique names, lightning bugs and fireflies are actually the exact same thing: a family of flying beetles that communicate through bioluminescent flashes. However, there is a reason for the differing terms—and it all comes down to where you live.

Are fireflies different from lightning bugs?

Again, lightning bugs and fireflies are the exact same insect. Adding another layer of confusion, they aren’t even flies at all—as members of the Lampyridae family, the bugs are technically winged beetles.

There are about 170 species of lightning bugs living in North America, according to Firefly Research and Conservation (FRC), a nonprofit organization dedicated to the insects. Each species has unique color and flash patterns, explains Akito Y. Kawahara, Ph.D., associate professor and curator at the Florida Museum of Natural History at the University of Florida, with purposes ranging from mating to carnivorous feeding (more on that later).

Why do they have two different names?

The terms “firefly” and “lightning bug” are the result of distinct regional dialects—and the one you use might actually tell you more about yourself than the insects.

Researchers from the University of Cambridge asked 10,000 Americans from around the country this question: “What do you call the insect that flies around in the summer and has a rear section that glows in the dark?” The results showed pretty clear differences in certain parts of the United States.

Roughly 40% of respondents used both terms interchangeably, 30% said “firefly,” and the remaining 30% said “lightning bug.” “Firefly” was most popular in the western half of the country, while “lightning bug” dominated parts of the Midwest, the South, and the Mid-Atlantic. The terms were largely interchangeable around that region, including on the East Coast and in Texas. (Two people said they use the term “peenie wallie”—we can’t explain that one, either.)

Another researcher later found that using “lightning bug” is more common in parts of the country where lightning strikes are more frequent. So although there’s no difference in the bugs themselves, there is a difference between the way we talk in certain places.

Why do these bugs light up?

Looking out at a field of these glowing insects, it’s easy enough to think of their flashes as just a pretty show—but the true purpose is far more complex. “What’s actually going on is quite amazing,” Kawahara explains. Their bioluminescence comes from a chemical reaction inside their bodies, and the insects flash for two main reasons: mating and feeding.

Male and female fireflies both flash, but the guys are typically the more active ones. “The males are calling the females using their light flashes,” Kawahara says, trying to woo available ladies with the right pattern and intensity.

On the other end of the spectrum, lightning bug flashes can also be a bit grim. “Predatory females attract males of another species so they can eat them,” Kawahara notes, by tricking them into thinking that a female of their own species is interested in them. “The males don’t know that, and they try to mate with the female, but they get eaten.”

Bummer. But at least they’re still beautiful, right?

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