Katydids produce a remarkably wide range of sounds, from the familiar raspy “katy-did, katy-didn’t” chirp that gave them their common name to ultrasonic frequencies far beyond what human ears can detect. Most species generate their calls by rubbing specialized structures on their forewings together, and the resulting sounds vary from musical pure tones to rapid-fire clicks, buzzes, and shuffling pulses. What makes katydid acoustics genuinely surprising is how much of their communication is invisible to us: many species sing at frequencies above 30 kHz, and some produce vibrations through the plants they sit on rather than through the air at all.
How Katydids Produce Sound
Katydids make sound using a mechanism called stridulation, which is fundamentally a friction process between their two forewings. During wing closure, a small lobe on the anal margin of the right forewing acts as a scraper, dragging across a row of teeth on the underside of the left forewing. That toothed ridge is called the file. As the scraper catches and releases each tooth in succession, the wing vibrates, and a large, thin wing cell called the mirror amplifies those vibrations into audible sound.1Journal of Insect Physiology. Complex wing motion during stridulation in the katydid Nastonotus foreli (Orthoptera: Tettigoniidae: Pseudophyllinae) Think of it like running your fingernail across the teeth of a comb, except the comb is built into one wing and the nail into the other, and a drum-like membrane broadcasts the result.
The spacing of the teeth on the file, the speed of the wing stroke, and the size and shape of the mirror all influence what the call sounds like. Species with evenly spaced teeth and a large, well-tuned mirror tend to produce clear, tonal sounds, sometimes described as musical. Species with irregular tooth spacing or a small mirror tend to produce broader, noisier calls, more of a buzz or rasp. This is why two katydid species sitting on the same bush can sound completely different from each other.
The Frequency Range Is Enormous
If you hear a katydid, you are probably hearing a call somewhere in the range of 5 to 30 kHz. That covers everything from a low-pitched chirp (around the upper range of comfortable human hearing) to a sound that many adults over 40 would struggle to detect at all. But some katydids operate well beyond that range. Males in the genus Supersonus, a group of tiny neotropical katydids, call at 115, 125, and even 150 kHz, placing them among the highest-frequency sound producers in the animal kingdom.2PubMed Central. Shrinking wings for ultrasonic pitch production: hyperintense ultra-short-wavelength calls in a new genus of neotropical katydids (Orthoptera: Tettigoniidae) Those frequencies are roughly five to seven times higher than the upper limit of human hearing, so a Supersonus katydid could be calling right next to your ear and you would hear nothing.
Other species fall between these extremes. A false-leaf katydid recently described from the Neotropics produces a peak frequency around 23.4 kHz, with a secondary fundamental peak near 11.7 kHz.3Elsevier. Auditory system biophysics in a new species of false-leaf katydid (Tettigoniidae: Pseudophyllinae) supports a hypothesis of broadband ultrasound reception That primary peak sits just above the range most adults can hear, though a teenager with sharp hearing might catch the fundamental. The upshot is that when you walk through a tropical forest at night and hear a few katydids chirping, there could easily be dozens more calling around you in frequencies your ears simply cannot access.
What Common Species Sound Like to Human Ears
For people in eastern North America, the most recognizable katydid sound comes from the common true katydid (Pterophylla camellifolia), which produces a loud, pulsing rasp from high in deciduous trees on summer nights. Each call consists of two or three quick bursts separated by brief pauses, producing the classic “katy-did” or “katy-did-n’t” rhythm. The tone is harsh and buzzy rather than musical, somewhere between a coarse whisper-shout and the sound of running a thumbnail across stiff cardboard.
Meadow katydids in the genus Conocephalus sound very different. They produce continuous, high-pitched buzzes or lisping trills that blend into the general background hum of a summer evening. Because their calls sit at higher frequencies, some people hear them as a constant faint hissing in grassy areas, while others with age-related hearing loss cannot hear them at all.
Coneheaded katydids (Neoconocephalus) are loud enough to be startling. Their continuous, intense buzzing can hit pain-threshold loudness at close range and sounds like a sustained electrical buzz. These species often call from tall grass or reeds, and anyone who has walked through a meadow on a warm night and heard what sounds like a malfunctioning power line has likely been standing next to a conehead.
Tropical species add even more variety. Some produce single sharp clicks. Others generate long, rattling series of pulses. A few produce sounds that are almost tonal and bell-like. The differences serve an essential purpose: in habitats where dozens of katydid species share the same patch of forest, each species needs a call distinct enough that females can pick out the right males from the noise.
Duetting Between Males and Females
In many katydid families, especially the large subfamily Phaneropterinae, communication is not a one-way broadcast. Instead, the male produces a call and the female answers with a precisely timed reply, creating a duet. The male then uses the female’s reply to locate her. This is different from the approach used by crickets and many other singing insects, where females are silent and simply walk toward the loudest male.
The female reply is usually much quieter and shorter than the male call, often just one to three brief clicks.4PubMed Central. High-speed duetting – latency times of the female acoustic response within the bush-cricket genera Leptophyes and Andreiniimon (Orthoptera, Phaneropteridae) An Australian bush-cricket species illustrates this well: the female times her reply within roughly a second after the male finishes his call and adjusts the number of clicks based on the male’s call duration and loudness.5PubMed. Female reply strategies in a duetting Australian bushcricket, Caedicia sp. (Phaneropterinae: Tettigoniidae: Orthoptera) She fits the entire reply into a narrow time window, suggesting that the timing carries information the male uses to verify species identity and direction.
Precision varies between species. In Amblycorypha alexanderi, females respond with a nearly constant delay of about 280 milliseconds, with very little variation from one reply to the next.6Annals of the Entomological Society of America. Calling Songs, Duets, and Auditory Tuning in Two Cryptic Katydids (Tettigoniidae: Phaneropterinae: Amblycorypha) A closely related species, A. rotundifolia, showed far more timing variation. These two species look nearly identical and can only be reliably told apart by their songs and duet timing, making acoustics the primary way they stay reproductively isolated from each other.
Sounds You Cannot Hear: Substrate Vibrations
Airborne sound is only part of the picture. Many katydids also communicate through vibrations transmitted directly through the plants they sit on. Males shake their bodies rapidly, a behavior called tremulation, which sends low-frequency vibrations through stems and leaves. Females can detect these vibrations through sensory organs in their legs and may respond with vibrations of their own.
In the meadow katydid Conocephalus nigropleurum, males produce substrate-borne vibratory signals specifically during courtship and mate attraction.7Behaviour. Courtship Communication in Meadow Katydids: Female Preference for Large Male Vibrations In the true katydid Nesoecia nigrispina, both sexes produce tremulatory vibrations during courtship, and males also vibrate the substrate after completing their calling song cycle and after mating.8PubMed Central. Acoustic and vibrational signaling in true katydid Nesoecia nigrispina: three means of sound production in one species
Research on neotropical false-leaf katydids has revealed something interesting about the relationship between these two channels. Species that produce louder, longer-range airborne calls tend to produce weaker substrate vibrations, and vice versa. The two signaling modes appear to compensate for each other, as if each species allocates its communication effort between air and plant depending on which channel works best in its particular habitat.9PubMed. Levels of Airborne Sound And Substrate-borne Vibration Calling Are Negatively Related Across Neotropical False-leaf Katydids This means that a katydid you never hear singing in the air might actually be calling vigorously through the branch it is standing on.
Protest Sounds and Defensive Noise
Not all katydid sounds are about finding mates. When grabbed or disturbed, many species produce protest sounds that differ markedly from their calling songs. In Nesoecia nigrispina, researchers documented three distinct types of defensive sound production in a single species. Males respond to touch by producing long series of syllables using their stridulatory apparatus, similar to their calling mechanism but with a different pattern. Both males and females also produce quieter sounds by rubbing their hind wings together, and both sexes generate sharp, loud clicks using their mandibles, apparently aimed at startling predators.10bioRxiv. Acoustic and vibrational signaling in true katydid Nesoecia nigrispina: three means of sound production in the one species
If you have ever picked up a large katydid and had it produce a sudden, loud click or buzz in your hand, that was a protest sound. Some larger tropical species can produce startlingly loud defensive noise, enough to make you flinch and drop them, which is precisely the point.
Competitive Calling and Female Preferences
When multiple males call in the same area, things get competitive. In choruses of the neotropical katydid Neoconocephalus spiza, females strongly prefer the male whose call starts first. This is not simply about loudness drowning out competitors. Researchers found that females avoided any male call that began in the interval right after another male’s call started, even when the later call was not physically overlapped by the first one. The preference held as long as the follower’s call was not more than a couple of decibels louder than the leader’s.11ScienceDirect (Elsevier / Animal Behaviour). Females prefer leading males: relative call timing and sexual selection in katydid choruses This “leader advantage” appears to be a perceptual effect: the female’s auditory system locks on to the first sound it detects and suppresses attention to later arrivals, similar to a precedence effect known from human hearing research.
The consequence is that male katydids in a chorus are under intense pressure to call first or to call louder than their neighbors. This helps explain why choruses of certain species can be almost deafeningly loud: each male is trying to edge ahead of the others in timing and amplitude. It also means that a male calling alone has a substantial advantage, which may be why some species spread themselves out rather than clustering together.
A Katydid That Mimics Cicadas
One of the stranger acoustic stories in the katydid world comes from Australia. The predatory katydid Chlorobalius leucoviridis has learned to lure male cicadas to their deaths by imitating the wing-flick signals that receptive female cicadas use to reply to courting males. The katydid produces tegminal clicks and synchronized body jerks that convincingly mimic the cicada’s reply, fooling males of multiple cicada species into approaching.12PLoS ONE. Versatile Aggressive Mimicry of Cicadas by an Australian Predatory Katydid The mimicry is versatile, meaning the katydid can adjust its fake replies to match different cicada species, which makes it an unusually flexible predator. This is one of the few documented cases of an insect using acoustic deception to hunt.
How Temperature Changes the Song
If you listen to katydids on a hot night versus a cool one, you will notice a difference. Warmer temperatures speed up the pulse rate and shorten the intervals between buzzes, while cooler temperatures slow everything down. This effect is consistent and predictable enough that some old naturalists’ guides included formulas for estimating the temperature from katydid chirp rates. Research has confirmed statistically significant effects of temperature on pulse rate, buzz duration, and the silent gaps between buzzes across multiple katydid species.13Journal of Orthoptera Research. Effects of Increasing Temperature on Acoustic Advertisement in the Tettigoniidae
This matters for more than just novelty. Because female katydids rely on call timing and rhythm to identify the right species, temperature shifts the entire communication system. Both the male’s call and the female’s auditory preferences shift with temperature in a coordinated way, which keeps the system functional across a range of conditions. But it also means that recordings made on a hot night and a cool night can sound like different species to an untrained ear, a common pitfall for amateur naturalists trying to identify katydids by sound.
Ears in Their Legs
Katydids hear with organs located in their front legs, just below the knee joint. These ears are structurally remarkable: they have outer, middle, and inner components, loosely analogous to the mammalian ear, making them unique among arthropods. Sound enters through two small tympanic membranes on each leg and also reaches the inner ear through a narrow canal derived from the respiratory tracheal system.14PubMed Central. A narrow ear canal reduces sound velocity to create additional acoustic inputs in a microscale insect ear The fact that sound arrives through both external and internal pathways gives the katydid a way to compare inputs and determine the direction a sound is coming from, even though the ears are separated by only a few centimeters.
This dual-input system helps explain how a female katydid can pinpoint a calling male in a noisy nighttime chorus, or how a duetting pair can locate each other across several meters of dense vegetation. It also means that when researchers play recorded calls through speakers, the katydid’s response depends on where the speaker is placed relative to its front legs, not its head.
Katydid Calls in the Fossil Record
Because the stridulatory structures on katydid wings are made of hardened cuticle, they fossilize well. This means scientists can look at the file teeth, mirror shape, and wing dimensions of fossil katydids and estimate what frequencies those ancient insects might have produced.15PubMed Central. Reconstruction of an extinct soundscape reveals ultrasonic communication in the Jurassic One Jurassic fossil, Archaboilus musicus, preserved well enough for researchers to determine that it produced pure-tone musical calls tuned at a frequency around 6.4 kHz, roughly a high-pitched whistle by human standards.16PubMed Central. Wing stridulation in a Jurassic katydid (Insecta, Orthoptera) produced low-pitched musical calls to attract females
Broader analysis of Mesozoic fossils suggests that katydids had already evolved complex acoustic communication, including mating calls, male-male signaling, and directional hearing, by the Middle Jurassic, over 160 million years ago. They also developed a wide diversity of singing frequencies, with evidence of acoustic niche partitioning, meaning different species divided up the available frequency space to avoid interfering with one another, as far back as the Late Triassic.17PubMed Central. High acoustic diversity and behavioral complexity of katydids in the Mesozoic soundscape In other words, the nighttime chorus of katydids, each species singing at its own pitch in its own rhythm, is not a recent phenomenon. It was already happening when dinosaurs were the dominant land animals.
Listening for Katydids with Technology
The fact that katydid calls are species-specific and acoustically distinctive has made them increasingly useful for ecological monitoring. Passive acoustic monitoring, in which autonomous recording units are placed in the field and the data are later scanned by software for target sounds, is now being used to track katydid populations across large areas.18Ecological Entomology. Large‐scale bioacoustic monitoring to elucidate the distribution of a non‐native katydid Building reliable automated detectors for katydids is challenging because training data are often unbalanced (some species are recorded far more than others) and because many calls are ultrasonic, requiring specialized microphones. Recent work on multi-species katydid detectors has shown that careful data engineering can overcome these issues, expanding passive acoustic monitoring into tropical insect communities where visual surveys are impractical.19PubMed Central. Extensive data engineering to the rescue: building a multi-species katydid detector from unbalanced, atypical training datasets
For anyone curious about identifying katydid calls in their own backyard, the practical barrier is usually frequency. A cheap smartphone microphone cuts off around 20 kHz, which means it can record the common true katydid or a conehead but will miss any species calling in the ultrasonic range. Dedicated bat detectors or ultrasonic recording equipment can capture those higher frequencies, and some hobbyist-grade models are available for a reasonable price. Even without special equipment, learning the rhythm and cadence of the species audible to you is a rewarding way to decode the nighttime soundscape. Each species has a signature that, once you learn it, becomes as recognizable as a birdsong.