Cicadas are known for the immensely loud acoustic signals that define the sound of summer. Although their sounds are sometimes mistakenly called a “chirp”—a term more accurately used for insects like crickets—cicadas instead create a sustained buzzing or singing sound. This distinctive sound is produced through a highly specialized biological process and serves as a sophisticated communication system.
The Mechanism of Cicada Sound Production
The ability to generate loud sound comes from a pair of complex organs called tymbals, located on the sides of the male cicada’s abdomen. These tymbals are ribbed, rigid sections of the exoskeleton modified to produce sound through “tymbalization.” A powerful, specialized muscle attaches directly to this structure.
When the tymbal muscle rapidly contracts and relaxes, it causes the ribbed membrane to buckle inward, creating a distinct, high-speed click or pulse of sound. Each of the ribs snaps inward sequentially. The muscle contraction rates are extremely fast, ranging from 120 to 480 times per second, causing the individual clicks to blend into a continuous, high-pitched buzz to the human ear.
The cicada’s body functions as a highly efficient natural amplifier to broadcast sound over long distances. The male’s abdomen is largely hollow, containing air-filled sacs that act as a resonance chamber. This hollow space significantly amplifies the sound pulses generated by the tymbals. Some species can produce sounds exceeding 106 decibels, making them the loudest insects in the world.
The Behavioral Purpose of Cicada Song
The constant chorus produced by cicadas is a purposeful form of communication, generated almost exclusively by the males. The primary function of the song is to attract females for mating and establish a chorus where both sexes gather. Each of the thousands of cicada species has a unique song pattern, ensuring that males attract only females of their own kind.
The sheer volume of the sound helps overcome environmental background noise, allowing the mating call to be heard by females over a mile away in some cases. The formation of large choruses is a collective strategy, as synchronized singing draws in more females. The song also plays a role in establishing territory and warning off rival males.
The loudness of the call is influenced by environmental conditions, as the sound-producing muscles operate best when the temperature is warm. Consequently, singing often peaks during the hottest part of the day. Females are equipped with tympana, specialized hearing organs on the underside of their abdomen, which allow them to perceive the frequency and pattern of the male’s calls.
Distinguishing Different Cicada Sounds
The acoustic repertoire of the male cicada is more varied than a simple buzz, consisting of several distinct signals used in different behavioral contexts. The most recognizable sound is the Calling Song, which is the loudest and most sustained signal. This chorus attracts both males and females to a specific location for potential mating.
Once a female is nearby, the male switches to the Courtship Song, which is quieter, more intricate, and often broken into short phrases. This signal is used at close range to persuade the female to mate. In some species, this involves a signaling duet, with the female responding to the male’s call by producing a quick wing-flick or click.
A third type of sound is the Distress Squawk or Protest Song, which is a frantic, non-rhythmic, and broken sound. This sound is produced when the insect is captured, handled, or attacked by a predator. While the calling and courtship songs are produced only by males using their tymbals, both sexes are capable of producing this distress call when threatened.