How Cicadas Create That Distinct Noise

Cicadas emit one of the most distinct sounds of the animal kingdom—of the insect group, anyway. The song of the cicada is a reverberating noise that's hard to describe and even harder to re-create. Cicada calls are hard to miss. It's just not summer without the hum of cicadas in the background on Southern evenings.

You've likely been familiar with cicadas for a long time, but exactly how do these insects make the sounds we associate with our Southern summers? There's a lot to learn about these small but mighty noisemakers.

What Are Cicadas?

Cicadas belong to a superfamily, the Cicadidae, and there are more than 3,000 known species of cicadas. These exceptionally loud bugs have been present in North America for millions of years. Having been around for as long as they have, cicadas have served many purposes in various cultures—as religious symbols, as good luck charms, as a food source, for medicinal purposes, and as an indication of a change in weather and changing seasons. Cicadas even make an appearance in cultural mythologies, literature, and music.

How Do Cicadas Make That Noise?

A team of U.S. Naval researchers analyzed the cicada's sound and explained that "the insects manage to produce their incredibly large sound because they have a unique anatomy that combines a ribbed membrane on the torso that vibrates when they deform their bodies." In other words, it's not vocal cords making that buzzing cicada sound.

Derke Hughes, a research engineer at the Naval Undersea Warfare Center, describes this process as such:

"If your body were like that of a cicada, […] you would have a thick set of muscles on either side of your torso that would allow you to cave in your chest so far that all your ribs would buckle inward one at a time into a deformed position. Releasing the muscle would allow your ribs to snap back to their regular shape and then pulling the muscle again would repeat this. The cicada repeats this cycle for its left and right sides about 300 to 400 times a second."

It's a unique system of noisemaking, and the result is a phenomenon we hear echoing across the landscape once the soil warms up and the cicadas emerge from the ground.

Why Do Cicadas Make This Noise?

Male cicadas "sing" with their thoraxes to attract mates. Females also make noise to attract the opposite sex of their species, but they don't vibrate their torsos like males do. Instead, they click their wings—a more subtle noise compared to the overwhelming drone of male cicadas.

What Month Do Cicadas Start Making Noise?

When cicadas begin to sing depends on where you live. That's because they wait until the soil temperature reaches 64° F to emerge. This could occur anywhere from April to June depending on your local climate and how far South you live.

How Loud Are Cicadas?

One of their defining features is the sheer volume of their singing, which can reach as much as 90-100 decibels, according to measurements taken by some journalists. While this is very loud—somewhere around the level of a lawnmower—the volume reduces the farther away you are from the insects. Of course, if you are going to be around cicadas at top volume for an extended period of time, the CDC suggests considering ear protection.

What Other Sounds Do Cicadas Make?

Cicadas are known for a pulsating drone or buzz, but that's not the only sound they make. According to the U.S. Geological Survey, "The sounds include courtship calls and squawking sounds when the cicada is handled or disturbed." If you're curious, you can hear an audio recording of the sounds of cicadas here.

Along with buzzing and squawking, different cicada species are known to produce rhythmic ticks, high-pitched whines, and an even more musical-sounding song.

What Is A Cicada's Life Span?

Cicadas emerge in routine intervals of either every 13 or 17 years, which usually occurs in May or June as they prefer warm, dry weather. Once they emerge, they spend about four to six weeks mating and laying eggs in the openings of the bark on tree trunks and branches. At least, this is true of periodical cicadas, a genus exclusive to North American regions known as Magicicada. Annual or dog-day cicadas emerge every year, as the name suggests.

While cicadas are above ground for only a few weeks, their life span is a lot longer. They can have a life span of 10 to 20 years, depending on the species. Some cicadas spend most of their time underground as nymphs, a stage that can last 15 years. They do not live long after becoming adults. The stage usually only lasts a few weeks, long enough to lay eggs.

Why Do Cicadas Take 17 Years To Come Out?

Whether it's 17 years or 13, periodical cicadas probably emerge on a staggered schedule to avoid being eaten. Scientists believe that more cicadas survive in massive swarms since predators can only eat so many. This adaptation also makes it harder for predators like parasitic wasps to specialize in feeding on them.

Do Cicadas Help Or Harm?

Despite the sometimes deafening sounds they produce and the fact that they descend upon us by the millions, these insects are harmless, to both humans and our pets. They do not bite or sting and will do little more than squawk if you disturb one. So, unless you just have an (understandable) insect phobia, you have nothing to be afraid of.

Cicadas don’t damage crops or bite humans or animals, so there’s no need to prevent or destroy them. They help the environment by aerating the ground as they build underground tunnels, which help water penetrate the ground. They also provide a food source for birds, bats, and reptiles. As they decompose, their bodies provide nutrients for the soil.

Keep an ear out—you're sure to hear the telltale cicada drone if you step outside during the warm months.