The sudden, collective silence of a cicada chorus often causes people to wonder why the intense buzzing abruptly stops. This phenomenon is directly related to the unique mechanical process cicadas use to create their calls, allowing for an instantaneous halt to the sound. Their loud songs, which can reach over 100 decibels, are not produced by vocal cords but by specialized organs that can be switched off instantly. The reasons for this immediate cessation are driven by environmental conditions and a survival reflex.
The Abrupt Silence Mechanism
Cicadas produce their distinctive sound using a pair of structures called tymbals, located on the sides of the male’s abdomen. Each tymbal is a ribbed, membrane-like plate that is buckled inward by the rapid contraction of a powerful, specialized tymbal muscle. This muscle action causes the stiff ribs to click or buckle one after another in quick succession, generating the initial sound pulse.
The tymbal muscle is one of the fastest contracting muscles known in the animal kingdom, capable of contracting and relaxing hundreds of times per second. This allows for the continuous, high-frequency call. To stop the noise, the cicada simply ceases the rapid twitch contractions of this muscle, achieving silence instantly because the sound production is mechanical.
The male cicada’s abdomen is largely hollow and functions as a resonating chamber, amplifying the small clicks into the loud, sustained buzz. Sound is further modulated by accessory muscles and by flaps called opercula which can move to expose or cover the tymbals. The ability to instantly stop the contraction of the main tymbal muscle is the core reason the chorus can go silent in a fraction of a second.
Temperature and Time of Day
Cicadas are ectothermic, meaning their activity levels are regulated by the external environment. This is a primary factor in their sound production, as most species require the air temperature to be warm enough for their tymbal muscles to function efficiently. Generally, they need temperatures above 72 degrees Fahrenheit (22 degrees Celsius). If the temperature drops below this threshold, the speed and power of the muscle contractions diminish, causing the chorus to fade or stop entirely.
This temperature dependency explains why the chorus often tapers off as evening progresses and temperatures fall. Most loud, daytime chorusing ends around sunset when the external heat source is removed. Cloudy skies or a sudden rain shower during the day can also cause a temporary reduction in calling volume for the same reason.
The cessation of sound at night also serves a behavioral purpose, as the male’s call is primarily meant to attract females for mating during the warmest part of the day. If conditions are no longer optimal for high-energy calling, the energetic cost of producing the loud song outweighs the benefit. The daily cycle of sound production balances reproductive drive and thermal tolerance.
Predator and Disturbance Response
One of the most dramatic reasons for a sudden stop is a behavioral response to perceived danger, acting as an instantaneous survival mechanism. Cicadas are skittish and will immediately cease their calling upon sensing a potential predator or a sudden environmental disturbance. This abrupt silence is a form of collective camouflage, as a silent, stationary insect is much harder for a visual predator to locate than a loudly buzzing one.
The sudden drop in volume is often a reaction to the movement or shadow of a flying bird, which is a common predator of adult cicadas. If an entire group is chorusing, a threat to one can trigger a rapid, synchronized silence across the whole aggregation. The loud, synchronized chorus is thought to be an anti-predator strategy, but this defense is immediately abandoned when a direct threat is detected.
The alarm response is not limited to natural predators; the sudden approach of a person or a loud, unexpected noise can have the same effect. This reflexive silence is a direct, immediate command to the tymbal muscles to stop contracting, demonstrating the insect’s ability to prioritize survival over the reproductive drive. The silence typically lasts until the perceived threat has passed, after which the chorus slowly begins to build back up.