Why Are Cicadas So Loud? How Cicadas Make Their Song

Why do cicadas sing?

Cicadas sing to find mates. Only males produce the loud calling song, and each species has its own pattern of buzzes, ticks or whines, so females can recognize males of their own kind even when several species sing in the same woods.

In periodical cicadas a receptive female answers a singing male with a precisely timed flick of her wings. The male moves toward her, switches to a quieter courtship song and mates. Males also make an alarm squawk when grabbed by a predator or a person, which may startle the attacker for long enough to escape.

Because the adult life of a cicada lasts only weeks, there is strong pressure to be heard quickly and over a long distance. A loud song lets a male reach females scattered across many treetops.

How do cicadas make such a loud sound?

A male cicada has a tymbal on each side of the first abdominal segment, just behind the wings. Each tymbal is a stiff, ribbed membrane, a little like the lid of a metal tin that pops in and out. A powerful muscle pulls on the tymbal, and the ribs buckle inward one after another, each producing a click. When the muscle relaxes, the elastic tymbal springs back, partly thanks to resilin, a rubbery protein.

The clicks follow each other so fast that they merge into a continuous buzz. In some species the two tymbals work alternately, doubling the rate. The sound is then amplified by large air sacs that fill most of the male’s abdomen. These sacs act like the body of a guitar, resonating at the frequency of the song, and in some species the thin eardrums on the underside of the abdomen help radiate the sound outward.

Many cicadas have plate-like covers called opercula over the sound organs. By raising and lowering the abdomen and these covers, a male can change the volume and tone of his song. Crickets work differently: they rub a scraper on one wing against a file on the other, as explained in Why do crickets chirp?, a method that cannot match the power of a cicada’s tymbals.

How loud are cicadas?

Cicadas are the loudest insects known. Sound levels depend on the distance from the singer, so measurements are usually given at a fixed distance.

The decibel scale is logarithmic, so a rise of 10 dB is roughly a doubling of perceived loudness. Some sources report cicadas reaching about 120 dB, but such figures usually come from measurements taken a few centimeters away. Even so, cicadas rank among the loudest animals for their size, as shown in the list of the loudest animals.

Why are cicada choruses so loud?

A single periodical cicada is loud, but an emergence can involve more than a million cicadas per acre. Males gather in “chorus centers”, often a few favorite trees, where hundreds or thousands sing at once. Their songs overlap and partly synchronize into a pulsing roar.

Choruses probably help males in two ways. A large chorus can be heard from farther away than a lone singer, drawing in more females, and a male in a crowd may be harder for a predator to locate. One popular claim is that the noise drives predators away, but studies of how predators actually respond do not support it.

When a brood emerges every 13 or 17 years, the sudden noise is one of its most famous features, a story told in Why do cicadas come out every 17 years?

Why do cicadas sing when it is hot?

Cicadas are cold-blooded, so their muscles work best when warm. Most species sing during the hottest hours of a summer day and slow down or stop in cool weather and at night. Many can raise their body temperature by basking, and a few can warm up by shivering their flight muscles.

This is why the buzz of “dog-day” cicadas is so closely linked to the hottest weeks of July and August in North America, and why periodical cicadas fall almost silent after dark. Temperature affects other singing insects too, as described in Can crickets tell the temperature? A few cicadas in tropical forests and Australia sing at dusk or even at night.

How do cicadas avoid deafening themselves?

Both male and female cicadas hear with tympana, thin membranes on the underside of the abdomen that work like eardrums. Because the tymbals and ears sit close together in the same hollow body, a singing male would risk damaging his own hearing. Males avoid this by partly disabling their own tympana while they call, yet they still need good hearing to detect the wing-flick replies of females and the songs of rival males.

Cicada songs in Europe

Europe has dozens of cicada species, most of them around the Mediterranean. In Provence in southern France, the summer song of cicadas such as Cicada orni is so familiar that the insect has become a regional symbol, and the large Lyristes plebejus is one of the loudest in Europe.

Britain has only one native species, the New Forest cicada, whose very high song, around 15 kHz, is too high-pitched for many adults to hear. It has not been confirmed in England since the 1990s, and conservationists have been working on bringing it back.