Hearing mysterious sounds from outdoors at night is a common experience, often sparking curiosity about their origin. Many of these nocturnal noises, from rhythmic chirps to buzzing hums, are not from unseen animals but rather from the diverse world of insects. These tiny creatures communicate through a variety of sounds, filling the night air with their unique calls.
Common Insects That Make Night Sounds
Among the most recognizable nocturnal sound producers are crickets, specifically field crickets and house crickets. Field crickets, often found in grassy areas, produce a steady, high-pitched chirp, a sound that can vary in speed depending on the ambient temperature. House crickets, smaller and lighter in color, typically inhabit warmer, sheltered environments like basements or crawl spaces and emit a similar, though sometimes softer, chirping sound.
Katydids, related to crickets but typically larger and green, are also prominent noisemakers in the night. Their calls are often described as a raspy “katy-did, katy-didn’t” or a series of distinct clicks, produced in trees and shrubs. Unlike the continuous chirps of crickets, katydid sounds often have a more irregular pattern, with pauses between phrases.
Cicadas, while some species are active during the day, many emerge and call most intensely during dusk and into the night, particularly in warmer climates. Their sound is a loud, often pulsating buzz or whirring noise, distinct from the chirps and rasps of crickets and katydids. These robust insects often congregate in trees, and their collective calls can be surprisingly intense.
How Insects Create Their Sounds
Stridulation
Stridulation is a common method where an insect rubs two specialized body parts together, creating friction that results in sound. Crickets and katydids, for instance, stridulate by rubbing their forewings together. One wing typically has a file-like structure, while the other has a scraper, and the rapid movement generates their characteristic chirps and rasps.
Tymbals
Cicadas, on the other hand, produce their loud calls using a different mechanism involving structures called tymbals. Tymbals are ribbed membranes located on the sides of the insect’s abdomen. Specialized muscles rapidly contract and relax, causing these membranes to buckle inwards and outwards at high speeds. This rapid vibration of the tymbals creates the buzzing or whirring sounds associated with cicadas, which are then amplified by air sacs within their bodies.
Why Insects Make Sounds at Night
The primary reason many insects produce sounds at night is for communication, particularly for attracting mates. Male crickets, katydids, and cicadas typically generate these calls to signal their presence and availability to females of their species.
The specific pattern, pitch, and rhythm of the call serve as a species-specific advertisement, ensuring that they attract only suitable partners. Females often respond to these calls or use them to locate males.
Beyond mate attraction, insect sounds can also serve other communicative purposes. Some calls may function in territorial defense, warning rival males to stay away from an established area. In certain instances, sounds might also be used as a warning to predators, indicating that the insect is unpalatable or difficult to catch. The nocturnal timing of these calls can also relate to environmental factors, such as cooler temperatures that reduce the risk of desiccation, or reduced predation pressure from diurnal animals.