A locust is a type of short-horned grasshopper that undergoes a dramatic transformation when population density increases. This change, triggered by crowding, causes the insect to switch from a solitary, shy phase to a highly mobile, gregarious, and swarming phase. Because many insects produce sounds, people often confuse the distinct noises made by locusts with those of other common buzzing or chirping creatures. The sounds produced by a locust are highly specific, serving different purposes depending on the insect’s phase and activity. Understanding these unique acoustic signals requires examining the characteristics and methods of their sound production.
Describing the Noise: Rattles, Buzzes, and Chirps
The sound produced by an individual locust is generally mechanical, described as a muffled buzzing, clicking, or rattle. These acoustic signals are often part of a communicative display, such as attracting a mate or defending a small territory. The pitch and rhythm of the chirping or buzzing pattern can vary significantly between different species of locusts.
A different, louder sound is produced during flight, known as crepitation. This loud, snapping, or cracking sound occurs when the insect rapidly expands and contracts its wings. In the context of a massive swarm, the individual sounds merge into a constant, overwhelming auditory experience.
A flying swarm produces a collective, immense noise due to the sheer number of bodies and wings moving simultaneously. This mass movement creates a consistent, low-frequency roar or hiss audible from a significant distance. The sound shifts from communicative chirps to a soundscape dominated by the friction and movement of millions of insects.
The Mechanics of Sound Production
The primary method locusts use to generate communicative sounds is called stridulation, which involves rubbing two specialized body parts together. This physical action is similar to running a pick along the teeth of a comb, resulting in short, rapid pulses of noise.
The locust rubs a row of small pegs on its hind legs against a hardened, textured vein on the forewing. This scraper and file system creates vibrations amplified by the wing structure, producing the audible buzzing or rattling sound.
These sounds serve as complex signals for intraspecies communication. The precise rhythm and frequency of the stridulation are used by males during courtship rituals to signal their species and readiness. They are also used for territorial displays to warn off rivals.
Confusing Sounds: Locusts vs. Cicadas and Grasshoppers
Locusts are fundamentally a type of grasshopper, so their sound production mechanisms are highly similar, relying on stridulation and crepitation. Both insects produce mechanical, pulsed sounds by rubbing the hind leg against the forewing, resulting in a characteristic rattling or buzzing noise.
Cicadas produce sound using a completely different anatomical structure. Male cicadas possess a pair of tymbals, which are ribbed, membranous organs on the sides of their abdomen. Muscles rapidly buckle these membranes, creating loud clicks that blend into a continuous, high-volume drone or scream.
The sound of a single male cicada can exceed 100 decibels. This volume and the continuous, high-pitched nature of the sound contrast sharply with the mechanical, lower-volume, and pulsed chirps of the locust. The difference in sound is a direct result of the difference in mechanism: a rubbing scraper versus a vibrating membrane.