Cicadas are among the loudest insects on Earth, their distinctive buzzing and chirping sounds becoming a prominent feature of summer landscapes in many regions. This volume sparks curiosity about how such a small creature produces such a loud sound. The science behind their extraordinary vocalizations involves specialized structures and an efficient amplification system.
The Mechanics of Cicada Sound Production
Male cicadas generate their characteristic sounds using a unique organ called the tymbal, located on each side of their abdomen. The tymbal is a ribbed membrane, and beneath it lies a powerful tymbal muscle. When the cicada rapidly contracts this muscle, the tymbal buckles inward. This inward buckling causes the stiff ribs within the membrane to snap, producing a distinct click.
As the muscle relaxes, the tymbal quickly returns to its original position, generating another click. Cicadas can repeat this process at an incredibly high speed, sometimes hundreds of times per second. The rapid succession of these individual clicks creates the continuous buzzing or whirring sound that humans perceive as a cicada’s song. This initial sound generation is a mechanical process, distinct from how many other insects produce sound by rubbing body parts together.
How Cicadas Achieve Extreme Volume
The initial clicks produced by the tymbals are then amplified by other structures within the cicada’s body. The male cicada’s abdomen is largely hollow, acting as a natural resonance chamber. This hollow cavity functions similarly to the body of a guitar, amplifying the sound waves. The size and shape of this abdominal cavity can influence the specific frequency and loudness of the sound, explaining why different cicada species produce varied calls.
Specialized flaps called opercula cover the tymbals and direct the sound outwards. These structures radiate the amplified sound into the environment. When many male cicadas sing together in a “chorus,” their combined efforts create a collective sound that can reach high volumes, sometimes exceeding 100 decibels. This synchronous chorusing contributes to the overall perceived loudness of a cicada emergence.
The Evolutionary Reasons for Their Loudness
The loudness of cicada calls serves evolutionary purposes. The primary reason male cicadas produce loud sounds is to attract mates. A louder call can signal a male’s fitness and enables him to attract females from a greater distance, increasing reproductive success. Each cicada species has a unique song, allowing females to identify and respond only to males of their own kind.
Beyond mate attraction, loud calls also serve as a defense mechanism. When disturbed or threatened, cicadas can emit distress signals. The sheer volume of a mass emergence can overwhelm potential predators, making it difficult for individual cicadas to be singled out. This “predator satiation” strategy, combined with their loud, disorienting calls, deters predators.