What Sound Do Crickets Make and Why?

The chirp you hear on a summer night comes from a male cricket rubbing his wings together. It isn’t made by his legs or by a voice. Nearly every chirp is a message to other crickets, and most of those messages are about finding a mate.¹ The same song that draws in females can also draw in enemies that hunt by ear, so every chirp carries a risk.

How a Cricket Makes Its Chirp

Plenty of people picture crickets rubbing their legs together, the way grasshoppers do in cartoons. Crickets actually use their front wings, raised slightly over the back. Only males have the sound-making equipment, so females don’t chirp.

A hard edge on one forewing, the scraper, runs along a vein lined with tiny teeth on the other forewing.² In field crickets the sound happens as the wings close, with the scraper snapping across the teeth one after another.³ Each tooth strike makes a tiny click, and about 5,000 strikes a second produce a tone of about 5,000 vibrations a second.⁴ The pitch you hear is set by how fast the teeth are struck, matched to the wing’s natural ringing pitch.⁵ Some bush crickets play the file the other way and sound on the opening stroke instead; one species has 54 broad teeth on its file.⁶ The wing behaves like a bell or tuning fork, sounding at its own natural pitch each time the teeth set it moving, so the result is a clean tone rather than a rasp.

A single chirp is really a short burst of several wing closings, each one a tiny pulse of pure tone. The gaps between chirps are when the wings reopen quietly.

Special thin wing panels then amplify the sound.⁷ Two of them vibrate strongly together and send most of the sound out.⁸ Even the lacy tip of the wing can vibrate along with them at the song’s pitch.⁹ Long, enlarged wings make a louder song but can ring at several similar pitches, which lets some males shift the pitch of their song.¹⁰

Behind the rhythm sits the nervous system. A dedicated nerve cell drives the singing rhythm, and stimulating it can make crickets produce song patterns.¹¹ A nerve centre in the abdomen times each wing stroke, and damage there leaves single clicks but no proper song.¹²

Why Crickets Sing, Calling, Courting and Fighting

The loud, steady chirping you hear at night is the calling song, a long-distance invitation to females.¹³ It is the loudest and most regular of a cricket’s songs, which helps females recognise the species and find the singer.¹⁴ In some field crickets females prefer faster and longer chirps.¹⁵ Faster chirping partly depends on how well a male has eaten, so it can advertise his condition.¹⁶

Males are the singers because females do the choosing. A female first checks that the pitch and rhythm match her own kind, then walks or flies toward the song she prefers.

Once a female is close, the male switches to a quieter, more varied courtship song.¹⁷ In one ground cricket this mix of soft and loud chirps alternates with calling, in displays lasting hours.¹⁸ Between males there is an aggression song, middling in loudness.¹⁹ Its timing reflects the male’s body size, which helps predict who wins a fight.²⁰ It signals how strong a male is, not how eager he is to fight.²¹

In your garden, a steady, regular chirp repeating for minutes is usually a calling song. Softer, irregular ticking near a second cricket often means courtship is under way. Sharp bursts when two males meet usually mean a territorial standoff.

Crickets also communicate up close by trembling their bodies or drumming on the ground or leaves.²² Males of every cricket group studied use these vibrations in courtship, guarding a mate and fights.²³

Chirp Speed and the Temperature Trick

A cricket’s body warms and cools with the air, so its singing muscles and nerves speed up on warm nights. In one field cricket, the warmth of the chest region affects song speed, while head temperature doesn’t.²⁴ Chest temperature doesn’t fully set the pace, so other parts of the nervous system also help set the rhythm.²⁵

The muscles and nerves run on chemical reactions that go faster when warm, so each wing stroke repeats sooner. Because the cricket’s body temperature follows the air, the chirp rate becomes a rough signal of air temperature. You can turn it into a thermometer:

Pick one cricket, since a chorus blurs together. Use a phone timer and count twice to check. The rule fits snowy tree crickets and common field crickets only roughly, and species differ, so treat the answer as an estimate within several degrees.

The same link explains why crickets go quiet in the cold. As evenings cool, chirping slows sharply, and on cold nights it may stop altogether. That is why chorus volume falls as autumn sets in.

Singing Is Hard Work

In mole crickets, calling can raise energy use to roughly 5 to 8 times the resting level.²⁸ In some crickets and katydids it rises 12 to 16 times above rest.²⁹ Singing can warm the chest by about 6 to 8 °C.³⁰ Louder songs and more time spent calling cost the most heat and energy.³¹ The expense falls on the male’s own reserves, so a male short on food has less to spend on calling, which is one reason his song reflects his condition.

You can hear the effect in the chorus. Males often sing in bouts with rests in between, and well-fed males can afford longer singing. Chirping often fades later at night as energy runs low and the air cools.

How Crickets Hear Without Deafening Themselves

A cricket’s ears are small eardrums just below the knee on its front legs. In some crickets the eardrum is as thin as 0.35 thousandths of a millimetre and very sensitive to high pitches.³²

Each leg has its own ear, so the cricket compares the sound reaching its left and right legs. Sound reaches the eardrum from outside and also through a breathing tube inside the body, which helps the cricket judge direction.

Each time a cricket chirps, the nerve carrying sound to its brain is suppressed, then switches back on between chirps.³³ The singing circuit sends a warning copy of each command to the hearing system.³⁴ So the cricket isn’t dulled by its own very loud song and can still hear rivals and females between chirps.³⁵

When a Song Attracts the Wrong Listener

A parasitic fly finds male crickets by homing in on their calling song.³⁶ The female fly follows the song until she reaches the singer, then drops larvae on the cricket.³⁷ The larvae burrow in and feed inside his body, and when they later emerge the host dies, so the encounter is fatal for him.³⁸

The fly’s hearing is unusual. Its two ears sit very close together, yet it can still tell which direction a sound comes from, because they are linked mechanically and respond to tiny differences in when sound arrives at each side. That precision lets it fly straight to a cricket, and engineers built a tiny direction sensor modelled on its ears.³⁹

Evolution can shift the balance quickly when a new enemy arrives, as happened in Hawaii. After the fly reached the islands, crickets and flies began a rapid evolutionary arms race over song.⁴⁰ On Kauai, in fewer than 20 generations, over 90% of males gained a mutant flat wing that can’t make sound.⁴¹

Silent males can’t call females.⁴² Instead, they gather near the few remaining singers and intercept the females drawn in.⁴³

Why Different Crickets Sound Different

Related species often differ in pitch or in pulse speed, and females prefer their own species’ version.⁴⁴ Where species live side by side their songs are more different, and females tell them apart accurately.⁴⁵ Two tree crickets sharing a habitat stay separate because females respond more to their own species’ calls.⁴⁶ Even populations of one species can drift apart, with Japanese field crickets singing higher and faster than European ones.⁴⁷ A female who mates with the wrong species wastes her eggs on offspring that may not survive or breed, so a distinct song lets her choose correctly before she gets close.

In a backyard chorus, a steady trill often comes from tree crickets in shrubs, though some other crickets trill too. Distinct chirp-chirp patterns are typical of field crickets on the ground. House crickets indoors give a sharp repeated chirp.

Clever Ways Crickets Get Louder

A small cricket’s wing moves air forward on one side and backward on the other, and the two cancel where they meet. The effect is strongest for low pitches and small wings, which is the usual situation for small crickets, and it weakens the sound.⁴⁸ Putting a barrier between the two sides stops the cancelling. Tree crickets do this by cutting a hole in a leaf and singing through it, using the leaf as a sound board.⁴⁹ The best boards follow three rules: a big leaf, a wing-sized hole, placed in the centre.⁵⁰ Mole crickets dig horn-shaped burrows tuned to their song’s pitch to make it louder.⁵¹

How Traffic Noise Changes Cricket Songs

In one test, 87% of tree crickets called in silence but only 61% did with road noise playing.⁵² Tree crickets near roads sing shorter bursts and pause more as traffic gets louder.⁵³ Field crickets living near highways chirp faster, especially when rival males are near.⁵⁴

Traffic noise covers the frequencies of cricket song, so a female may have trouble hearing the chirps. A male who keeps singing into the noise wastes energy if no one can hear him, so backing off or adjusting the song can make sense, depending on the species.