Cicadas are fascinating insects, widely recognized for the distinctive and often overwhelmingly loud sounds they produce. Their pervasive hum and buzz serve as a prominent natural soundtrack in many parts of the world. These insects are masters of acoustic communication, creating some of the loudest sounds in the insect kingdom. Their presence is most noticeable when large numbers emerge, filling the air with their unique calls.
How Cicadas Make Their Sound
Male cicadas produce sounds using specialized organs called tymbals, located on their abdomen. Tymbals are not like vocal cords; instead, they are ribbed membranes on the exoskeleton. Powerful muscles rapidly contract and relax, causing these tymbal membranes to buckle inward and then snap back, creating a series of rapid clicks. This action can produce 300 to 400 sound waves per second.
The sounds generated by the tymbals are then amplified by hollow abdominal cavities. These air sacs act as resonant chambers, increasing the volume. The tymbals and resonant abdomen allow cicadas to create continuous, high-pitched noises.
The Purpose of the Cicada’s Song
The main reason male cicadas produce songs is for reproduction. Their calls serve as mating signals, attracting females of their own species. Each species has a distinct song, ensuring males attract females of their own kind. These songs guide females to male aggregations, often referred to as choruses, where mating occurs.
Beyond attracting mates, cicadas also use sound for other communication purposes. They can produce alarm calls when disturbed, which are rough, buzzing sounds. Some species use aggregation calls to gather other cicadas, forming large, noisy groups. Females, lacking sound-producing tymbals, can respond to male calls with wing flicks or clicks.
Why the Noise is So Intense
The intensity of cicada noise stems from an individual insect’s sound output and the collective effect of many cicadas singing simultaneously. A single cicada can produce sounds over 100 decibels, making them among the loudest insects. This loudness is due to their efficient sound production mechanism.
The main factor contributing to the volume is “chorusing,” where numerous male cicadas gather and sing together. When millions or billions of cicadas emerge, especially periodical cicadas, their combined calls create an immense wall of sound that can be almost deafening. This synchronized singing amplifies the noise to levels comparable to a motorcycle from 25 feet away.
Variations in Cicada Calls
Cicada sounds are not uniform; different species produce distinct songs. This variation is crucial for species recognition during mating. The patterns, frequencies, and pitches of their songs allow cicadas to identify and attract mates from their own species.
Beyond species-specific mating calls, cicadas also have a repertoire of different sounds for various situations. For example, the alarm call, produced when threatened, differs from its mating song. Some cicadas also use wing flicks or stridulations to communicate, which adds to their acoustic signals. This diversity in calls highlights the complexity of cicada communication.