Cicadas are a familiar summer sound, their loud calls filling the air. This noise often prompts questions about its origin and duration.
The Purpose of Their Sound
Male cicadas produce loud summer noises. Their main purpose is to attract females for mating. Each species has a unique song, helping females identify mates.
Cicadas create sounds using tymbals, specialized organs on their abdomen. These ribbed membranes buckle rapidly when muscles contract, producing clicks. This rapid clicking creates the continuous buzzing or whirring sound. Their hollow abdomen acts as a resonance chamber, amplifying the sound. Some species produce sounds exceeding 100 decibels, comparable to a lawnmower or a motorcycle.
Daily Patterns of Cicada Noise
Cicada noise intensity and duration vary daily. As cold-blooded insects, their activity, including sound production, is influenced by temperature. They are most active and loudest during the hottest parts of the day, from late morning to late afternoon.
As temperatures cool in the evenings or during rain, cicada activity and calls diminish. This explains why the sound is constant on hot, sunny days but quiets when conditions are less ideal. Different species may have preferred singing times.
Distinctions Between Annual and Periodical Cicadas
Understanding annual and periodical cicadas helps comprehend their noise patterns. Annual cicadas, also known as dog-day cicadas, appear every summer. Though they emerge yearly, individual life cycles span two to five years, some up to ten years underground. Their staggered emergence means some adults mature and emerge each year, leading to a consistent summer presence.
Periodical cicadas, found mainly in eastern North America, have longer, more synchronized life cycles, emerging every 13 or 17 years. These emergences involve massive numbers appearing almost simultaneously in specific areas, known as broods. This synchronized emergence results in overwhelming, localized, and intense noise, distinct from the more scattered sound of annual cicadas.
Overall Noise Duration
Individual adult cicadas have a short lifespan, lasting four to six weeks above ground. However, collective noise can persist for several weeks. For periodical cicadas, once they emerge in late April or May, their mating calls last four to six weeks. The most intense noise peaks about a week and a half after initial emergence and continues for two more weeks before quieting.
Annual cicadas, with overlapping generations, contribute to summer’s background sounds throughout July and August. Thus, cicada noise ranges from a concentrated, multi-week event during a periodical emergence to a consistent, seasonal background hum. Emergence timing and noise duration are driven by the cicadas’ reproductive imperative, as their adult stage is solely for mating and laying eggs.