Cicadas are a familiar sound of summer, filling the air with their distinctive buzz. These insects are known for producing some of the loudest sounds in the insect world. Their acoustic displays are a defining characteristic of warmer months in many regions.
The Purpose of Cicada Calls
Cicada sounds serve several biological functions, primarily reproduction. Male cicadas produce loud, species-specific calls to attract females for mating. These acoustic signals help females locate suitable mates. The louder and more sustained a male’s call, the more attractive he may be to a potential partner.
Cicadas also use sound for aggregation, drawing other individuals of the same species together. These aggregation calls can help form choruses, where many males call simultaneously. This creates a powerful acoustic beacon that increases their chances of attracting females. Such gatherings also offer some protection against predators.
Cicadas employ distress calls when threatened or captured. These loud, erratic sounds can startle a predator, giving the cicada a chance to escape. They may also alert nearby cicadas to danger, prompting them to disperse.
The Mechanics of Sound Production
The sounds of cicadas are produced by specialized structures on their abdomen, primarily the tymbals. These are ribbed, drum-like membranes found on either side of the cicada’s body, near the base of its wings. Each tymbal is connected to powerful muscles.
When these muscles contract, they cause the tymbal membrane to buckle inwards, producing a distinct click. As the muscles relax, the tymbal springs back to its original position, creating another click. This rapid, repeated buckling and unbuckling of the tymbal, occurring hundreds of times per second, generates the continuous buzzing sound.
The cicada’s abdomen also plays a crucial role in amplifying the sound. Much of the abdomen is hollow, acting as a resonant chamber that greatly magnifies the volume produced by the vibrating tymbals. This natural amplification allows the insect to produce sounds that can be heard over long distances, sometimes exceeding 100 decibels at close range.
Diversity in Cicada Songs
Different species of cicadas produce unique calls, which are critical for species recognition and successful reproduction. These species-specific “songs” prevent interbreeding, ensuring that males attract females of their own kind. The intricate patterns and frequencies of these calls act as a biological password.
Within a single species, cicadas employ various types of calls for different communicative purposes. Males often have a general calling song, which is the loud, sustained sound used to attract females from a distance. Once a female is close, a male might switch to a softer, more intricate courtship song to entice her further.
Female cicadas, while not possessing tymbals, can produce their own sounds, such as wing-flick responses, to signal their presence and receptiveness to a male. Aggregation calls bring groups together, and distress calls are sharp, loud bursts that serve as an alarm when the insect is in danger. These varied acoustic signals highlight the complexity of cicada communication.