Cicadas are known for the distinct sounds they produce, a characteristic that makes them one of the most noticeable insects during warmer months. Their presence is announced by a pervasive, rhythmic hum that fills the air, particularly during late spring and summer. This audible phenomenon is a fundamental aspect of their biology and life cycle.
The Sound Producers
Male cicadas create their characteristic sounds using specialized structures called tymbals, located on the sides of their abdomen. These tymbals are ribbed, rubbery membranes. Muscles attached to these membranes contract and relax rapidly, causing the tymbals to buckle inward and then spring back, producing a series of distinct clicks. This rapid buckling generates the continuous buzzing or whining sound that humans perceive.
The cicada’s hollow abdomen plays a role in amplifying these clicks. Sound waves generated by the tymbals resonate within this hollow space, much like a sound box, making the noise louder. This natural amplification allows their sounds to travel over considerable distances. Different species of cicadas have varying abdomen sizes and shapes, which influence the unique sound produced by each species.
The Purpose of Their Chorus
The primary reason cicadas produce noise is for reproduction: males attract females. Male cicadas generate calling songs to signal their presence and readiness to mate. These species-specific songs help females identify suitable partners and prevent interspecies confusion. Males often gather in groups, creating a synchronized chorus that amplifies their collective sound, increasing their chances of attracting females.
Beyond mating calls, cicadas also produce other types of sounds. They emit courtship songs when a female shows interest, which are softer and more refined. Cicadas also produce distress or alarm calls when threatened. These sounds may serve as a warning to other cicadas or as a deterrent to an attacker.
Beyond the Buzz: Types and Loudness
Cicada sounds are notable for their intensity, making them among the loudest insects on Earth. Their calls can range from approximately 80 to 120 decibels (dB) at close range, with some African species recorded at 107 decibels. For perspective, 100 decibels is comparable to a lawnmower or a passing motorcycle. This loudness helps their communication signals carry over long distances, particularly in dense vegetation.
The characteristics of cicada sounds, including intensity and frequency, vary depending on the species, environmental conditions, and time of day. While calling songs are the most common, cicadas also produce courtship and alarm calls, each with distinct acoustic patterns. Though loud, direct exposure to cicada noise for a single instance is not harmful to human hearing, as damage usually results from repeated and prolonged exposure to high decibel levels.