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Why Are Cicadas So Loud? How Do Cicadas Produce Sound?

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Tymbal muscles and membranes of the periodic cicada.

Superfast tymbal muscles of male periodic cicadas (in yellow) generate rapid contractions (up to 50 times per second) that rattle a pair of stiffened tymbal membranes (in red) to emit high-pitch mating calls to attract females.

Image: National Institute of Arthritis and Musculoskeletal and Skin Diseases, NIH
Question: Why Are Cicadas So Loud? How Do Cicadas Produce Sound?

The sound of the cicada love song can be deafening. In fact, it's the loudest song known in the insect world. Some species of cicadas register over 100 decibels when singing. Only males sing, trying to attract females for mating. Cicada calls are species-specific, helping individuals locate their own kind when different kinds of cicadas share the same habitat.

Answer:

The Mating Call of the Male Cicada

The adult male cicada possesses two ribbed membranes called tymbals, one on each side of its first abdominal segment. By contracting the tymbal muscle, the cicada buckles the membrane inward, producing a loud click. As the membrane snaps back, it clicks again. The two tymbals click alternately.

Air sacs in the hollow abdominal cavity amplify the clicking sounds. The vibration travels through the body to the tympani, which amplify the sound further.

The Cicada Chorus

If a single male cicada can make a noise over 100 decibels, imagine the noise produced when thousands of cicadas sing together. Males aggregate as they sing, creating a cicada chorus. Together, the males sing and fly, landing on sunny branches near the tops of trees.

The Female Response – Wing Flicking

A female cicada that finds a male attractive will respond to his call by doing a maneuver descriptively called the "wing flick." As you might imagine, this involves a brisk movement of the wings. The male can both see and hear the wing flick, and will reply with more clicking of his tymbals. As the duet continues, the male makes his way toward her and begins a new song, called the courtship call.

The Alarm Call

In addition to its mating and courtship calls, the male cicada makes noise when startled. Pick up a male cicada, and you'll probably hear a good example of the cicada shriek. Similar to the mating call, the alarm call adds to the noise of the cicada population.

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