The common perception of a summer day often includes the loud, buzzing chorus of cicadas. Generally, these insects fall silent once the sun sets, but they can occasionally be heard after dark. The typical cicada sound is a specific mating call produced by the male as part of their reproductive cycle. While silence is the rule, the insects’ response to certain environmental factors can lead to an unexpected nocturnal concert.
The Daytime Concert: Sound Production and Purpose
The characteristic loud noise of a cicada is produced by a specialized organ called the tymbal. This structure is a ribbed, chitinous membrane found on the sides of the male’s abdomen. Muscles rapidly pull and release the tymbal, causing it to buckle and click hundreds of times per second. The abdomen is largely hollow, acting as a resonating chamber to amplify the sound, which can exceed 100 decibels in some species.
This powerful acoustic signal serves primarily as a species-specific calling song to attract receptive females and establish chorusing centers. Males often aggregate in trees with good sunlight exposure, forming large groups where they synchronize their calls. The female responds with a simple, species-specific wing-flick sound, signaling her location to a nearby male. Without the proper environmental conditions, this calling behavior ceases.
Environmental Controls: The Role of Light and Temperature
Cicadas are ectothermic, meaning their muscle function is regulated by the surrounding environment. They require a certain warmth threshold to be active enough for flight and singing. For many species, the minimum temperature for sustained calling is between 65 and 70 degrees Fahrenheit. As the air temperature naturally drops after sunset, the insects’ body temperature falls below the optimal range, leading to a reduction in activity.
Direct sunlight is another primary trigger for the collective chorusing behavior. The light cycle helps regulate the cicadas’ circadian rhythm, signaling the appropriate time for reproductive activity. Studies show that a sudden increase in light intensity, such as when the sun emerges from behind a cloud, immediately increases the strength of the calls. The absence of solar energy and the subsequent drop in temperature at night signal the insects to stop calling and rest.
Exceptions to the Silence
Despite the strong environmental cues that promote silence, cicadas can occasionally be heard at night. One significant factor is the presence of artificial lighting, which disrupts the insects’ natural rhythm. Bright streetlights or strong porch lights can confuse a cicada’s light-sensitive biological clock, mimicking the daylight conditions that trigger calling. In urban areas with light pollution, this confusion can cause males to continue their mating songs long after dark.
Certain tropical or desert-dwelling species are naturally crepuscular or even nocturnal, with peak activity occurring during warm nights. For instance, species like Cryptotympana atrata have been observed to sing when the ambient temperature remains high, sometimes between 75 and 86 degrees Fahrenheit.
Distress Calls
Any cicada, regardless of species or time of day, will produce a loud, frantic distress call if captured or handled by a predator. This alarm sound is purely defensive and is not part of the regular, environmentally controlled chorus.