Why Do Crickets Chirp? How and Why Male Crickets Sing

How do crickets make the chirping sound?

The chirp comes from the wings, not the legs. On the underside of each front wing of a male cricket runs a thick vein lined with a row of tiny ridges, called the file. Near the inner edge of the other wing is a hardened ridge called the scraper. When the male lifts his front wings and closes them, the scraper of one wing runs across the file of the other, like a fingernail drawn along the teeth of a comb.

Each tooth strike sets the wing vibrating. Thin, stiff areas of the wing, including a patch known as the harp, resonate and amplify the sound, much like the body of a guitar amplifies a string. A single chirp is a quick series of wing closures, and the song is built from many chirps repeated in a pattern that is typical for each species.

Making sound by rubbing body parts together is called stridulation. Crickets are not alone in using it: grasshoppers usually rub a hind leg against a wing, and katydids also use their wings. The differences between these insects are covered in grasshopper vs cricket.

Why do male crickets sing?

The main purpose of the song is to bring males and females together. A male cricket usually sings from a fixed spot, such as the mouth of a burrow or a crack in a wall, and females walk or fly toward the sound. Because each species has its own rhythm and pitch, a female can tell a male of her own kind from other singing insects nearby.

Many crickets use several distinct songs:

• Calling song: loud and repeated, it attracts females from a distance and tells other males that the spot is taken.
• Courtship song: quieter and more varied, sung when a female is close, it encourages her to mate.
• Aggressive song: sung when a male meets another male, often during a fight with antennae and jaws.

In many species the winner of a fight sings briefly afterward. Females are silent: they lack the file and scraper, and their job is to listen and choose.

How do crickets hear each other?

Crickets have ears on their front legs. Just below the joint that works like a knee, each front leg has a thin, oval membrane called a tympanum, which vibrates when sound reaches it, just like an eardrum. Air-filled tubes connect the two ears through the body, so the sound arrives at each eardrum by more than one path.

This arrangement lets a female compare the sound at her two legs and turn toward the louder side, homing in on a singing male. Females often prefer songs that are louder, more regular or sung for longer, which may signal a healthy, well-fed male.

Why do crickets chirp at night and in summer?

Most crickets, including the house cricket, are active mainly in the evening and at night. Singing in the dark helps a male avoid birds, lizards and other hunters that find their prey by sight. Calm night air also lets sound travel farther without being broken up by wind.

Crickets chirp most in late summer and early autumn in many temperate regions because that is when most species become adults. Young crickets, called nymphs, cannot sing because they have no fully formed wings. A few species, such as the European field cricket, mature earlier and sing mainly in spring and early summer.

Temperature affects the song too. Crickets are cold-blooded, so they chirp faster when it is warm and slower when it is cool. In some species this effect is so regular that the chirp rate can be used to estimate the air temperature, as explained in can crickets tell the temperature.

The risks of singing

Singing is dangerous. A chirping male reveals his position not only to females but also to predators and parasites. In North America, a parasitic fly, Ormia ochracea, finds field crickets by their song and deposits its larvae on them; the larvae then burrow into the cricket and usually kill it within a week or so.

On the Hawaiian island of Kauai, this fly became so common that a population of Pacific field crickets changed in just a few years in the early 2000s. Most males now carry a mutation that gives them flat, smooth wings without a working file and scraper, so they cannot sing. These silent males survive by staying close to the few singing males and intercepting the females that come to them.

Many crickets reduce the risk by falling silent at the slightest vibration or sound of footsteps, which is why a chirping cricket can be so hard to find.

Tricks for a louder song

Some crickets have found ways to make their songs louder. Mole crickets dig burrows shaped like horns, which work like a megaphone and help their calls carry across fields. Some tree crickets sing from a hole chewed in a leaf, using the leaf as a baffle that stops sound waves from the front and back of the wings canceling each other out.

Song volume matters because a louder male can attract females from a larger area.

Do all crickets chirp?

No. Most cricket species have singing males, but some are silent. Some ground crickets and cave-dwelling crickets have tiny wings or none at all and cannot stridulate, and they rely on touch, smell or vibration to find mates instead. The silent Hawaiian field crickets show that a species can even lose its song quickly when singing becomes too dangerous.