The sounds of summer are often defined by a loud, whirring chorus that seems to emanate from the trees during the hottest hours of the day. This persistent, high-volume buzz is a common feature of warm climates. The primary culprit behind this loud, daytime phenomenon is a large insect known as the cicada. Their sheer volume and relentless song make them the most likely source of overwhelming insect noise coming from the canopy.
Identifying the Primary Suspects
The cicada is a large flying insect distinguished by its stout body, prominent eyes set far apart on its head, and clear, veined wings. Cicadas belong to the order Hemiptera, the true bugs, and should not be confused with locusts, which are a type of grasshopper. Common types encountered are divided into two categories: annual and periodical cicadas.
Annual cicadas, often called “Dog-Day Cicadas,” appear every summer, typically from July through September. These species are usually larger, with dark green or black coloration and green wing veins. While their individual life cycles last two to five years, adults are present consistently because some mature each year.
Periodical cicadas are famous for their synchronized mass emergences that occur only every 13 or 17 years. These species are slightly smaller, characterized by black bodies, striking red eyes, and orange wing veins. Their synchronized emergence in the millions leads to periods of extreme loudness that can be heard for miles.
Although cicadas are the dominant source of daytime tree noise, other insects contribute to the summer chorus. Katydids are another well-known source of loud sound, though their calls are typically more high-pitched, staccato, and halting. Unlike the cicada, which sings primarily during the day, katydids are nocturnal singers, filling the summer nights with their distinct chirping.
The Mechanics of Insect Noise
Cicadas produce their loud sound using a unique biological structure, not by rubbing their wings or legs together like crickets or grasshoppers. The sound comes from a pair of specialized organs called tymbals, which are stiff, ribbed membranes located on the sides of the male insect’s abdomen. These tymbals are connected to powerful muscles that contract quickly.
When the cicada contracts these muscles, the tymbal membrane buckles inward, creating a distinct click. The muscle then relaxes, and the membrane snaps back into its original shape. This action is repeated hundreds of times per second, with each snap generating sound pulses.
The insect’s abdomen plays a significant role in amplifying the sound, acting as an acoustic resonance chamber. The cicada’s abdomen is hollow, containing enlarged air sacs derived from the tracheae. This hollow space amplifies the rapid clicks from the tymbals, allowing the sound to reach high decibel levels, sometimes over 100 decibels. The resulting sound is a continuous buzz or drone, making the cicada one of the loudest insects in the world.
Life Cycles and the Purpose of the Song
The intense noise produced by the male cicada serves a singular purpose: to attract a mate. Males use the loud chorus to establish a communal calling center that signals their presence to females of the same species. The song is species-specific, ensuring that females are drawn only to males of their own kind, even when multiple species coexist.
Once a female is attracted, she often responds to the male’s song with a wing-flick or clicking sound. This acoustic exchange confirms her willingness to mate, completing the primary goal of the male’s performance. The sounds that humans hear are almost exclusively these mating calls, though cicadas also produce a distinct, frantic buzz as a distress or warning call if they are captured or disturbed.
The singing phase represents the culmination of a long developmental period spent underground. Cicadas spend most of their lives as nymphs, burrowed into the soil and feeding on the xylem fluid from tree roots. This subterranean stage can last for years; for annual cicadas, it is typically two to five years, while periodical cicadas remain underground for 13 or 17 years.
When the ground temperature reaches the appropriate level, the mature nymphs emerge, crawl onto a vertical surface, and molt into their winged adult form. The singing and mating rituals then occur during the brief adult stage, which lasts only a few weeks. This short lifespan above ground is dedicated to reproduction before the adults die, and the newly laid eggs begin the long cycle anew.