The noise of cicadas is one of the most distinctive sounds of summer. These insects spend most of their lives underground, emerging to make their presence known through a remarkable acoustic display. The volume and persistence of their song often prompt questions about its origin and purpose, especially since some species can produce sounds exceeding 100 decibels.
Communication and Courtship
The primary purpose of the cicada’s sound production is to attract a mate. Only male cicadas possess the anatomy necessary to generate the species’ loud, characteristic song. Males often gather in large numbers to synchronize their calls, creating a chorus or congregational song. This collective sound establishes a singing center, acting as an acoustic beacon to draw in females.
The specific pitch and rhythm of the song are unique to each species, allowing females to identify and locate a male of the correct type. Synchronized calling helps the sound travel farther and overcome background noise, increasing the chance of attracting a receptive female. Once drawn close, the female may signal her presence and willingness to mate by making a distinct, timed flick of her wings.
The Anatomy of Sound Production
The cicada’s song involves a pair of specialized organs called tymbals, located on the sides of the male’s abdomen. A tymbal is a thin, ribbed membrane connected to an internal muscle. Sound is produced not by rubbing body parts together, like crickets, but through the rapid mechanical buckling of this membrane.
When the cicada contracts the tymbal muscle, the membrane buckles inward, producing a distinct click or pulse. The muscle then relaxes, allowing the tymbal to spring back to its original shape, which generates a second click. This process repeats extremely quickly, with contractions occurring hundreds of times per second, resulting in a continuous, buzzing tone to the human ear.
The volume of the cicada’s song is achieved through natural amplification. The insect’s abdomen is largely hollow and acts as a resonance chamber. This empty space increases the output of the rapid tymbal clicks, turning small, internal sounds into a powerful, far-reaching song. Some species can also modulate their sound by flexing their abdomen toward or away from the resting surface.
Understanding the Different Calls
Male cicadas possess a repertoire of calls used in different social contexts. The most familiar sound is the loud, continuous calling song or congregational song, which is used for long-distance mate attraction.
The courtship song is produced when a female is nearby and the male is attempting to mount her. This short-range signal is often more intricate than the calling song.
When a cicada is seized by a predator or handled, it will often produce a third type of sound, known as a distress or alarm call. This erratic, broken buzzing is likely intended to startle an attacker or alert other nearby insects.