Cicadas are one of nature’s loudest insects, filling the summer air with their intense, whirring chorus. The massive volume of their calls naturally leads to the question of how they manage to hear in such a noisy environment. Cicadas possess highly specialized auditory organs that allow them to process sound with great precision, enabling them to communicate effectively despite the surrounding clamor.
Sensory Organs and Location
Cicadas do not have external ear structures like those found on mammals and other vertebrates. Their hearing apparatus, known as the tympanal organs, are internal structures that function as biological eardrums. These organs are situated on the underside of the insect’s abdomen, specifically located on the first abdominal segment. Both male and female cicadas possess these membranous structures, which are formally called the tympana.
The tympana (hearing organs) must be distinguished from the tymbals (sound-producing structures) found only on males. The tymbals are ribbed membranes located on the sides of the abdomen that rapidly flex to create the loud singing noise. The tympana, in contrast, are solely for receiving and processing acoustic vibrations.
How Sound Waves Are Processed
The tympanum is a thin, mirror-like membrane stretched over an air sac, functioning much like a drumhead. Airborne sound waves cause this delicate membrane to vibrate, and these physical movements are then converted into neural signals. A short tendon connects the tympanum to a complex auditory organ that houses a large number of sensory cells, sometimes numbering over a thousand receptors in each ear.
This auditory organ transforms mechanical vibrations into electrical impulses that travel to the cicada’s nervous system. When a male cicada begins its loud call, which can exceed 120 decibels, a specialized muscle contracts. This contraction pulls on the tendon connected to the tympanum, creasing the membrane and temporarily muffling the male’s own hearing to prevent damage from its high-volume song.
Beyond detecting airborne sounds, some cicadas are also capable of perceiving vibrations through the substrate. This dual sensitivity allows them to detect movement or communication signals transmitted through solid materials as well as through the air. For some species, the airborne song generates a secondary substrate vibration that is also detected.
The Essential Function of Cicada Hearing
The function of the cicada’s hearing is to facilitate species-specific communication and reproduction. The loud calls produced by the males act as an acoustic beacon to attract females of the same species over long distances. A female’s ability to hear allows her to distinguish the unique frequency and rhythm of her own species’ call from the calls of other cicada species.
Once a female is attracted to a male’s song, she will signal her readiness to mate by producing a species-specific response, such as a quick flick or snap of her wings. The male must hear and correctly interpret the timing of this subtle auditory cue to locate and approach her. Male hearing also supports the formation of large singing groups, known as choruses, which increase the overall volume and attraction power.
Survival is also a function, as the intense collective noise may help repel predators like birds. The ability to hear also enables cicadas to perceive alarm calls or the distress signals of other individuals.