Moths, often perceived as silent, nocturnal insects, can produce various sounds. These sounds serve important functions, from evading predators to communicating with potential mates.
The Silent Majority of Moths
Most moth species are generally silent to human ears. They do not possess vocal cords or other easily discernible sound-producing organs. Their primary communication relies on chemical signals, such as pheromones, which attract mates over significant distances. Visual cues also play a role in their interactions, particularly in species active during daylight or twilight hours.
The Sounds Some Moths Make
Certain moth species have evolved unique methods for sound production, ranging from ultrasonic clicks to audible squeaks. Some moths, like tiger moths and ermine moths, produce ultrasonic clicks using specialized organs called tymbals. These tymbals are located on the thorax or wings and can snap to create rapid bursts of sound, typically beyond human hearing. Ermine moths, for instance, generate ultrasonic clicks twice per wingbeat cycle through a corrugated membrane in their hindwings.
Other moths produce sounds that are audible to humans. The Death’s-head hawkmoth, for example, is known for its distinct squeaking or chirping sound. This sound is created by expelling air through its pharynx, which is uniquely adapted with a thick proboscis. Very large moths can also produce a low hum from the rapid beating of their wings during flight.
Why Moths Make Noise
The sounds produced by moths serve several adaptive purposes, primarily for survival and reproduction. Many moths use ultrasonic clicks as a defense mechanism against predatory bats, which rely on echolocation to hunt. These clicks can “jam” the bats’ sonar, creating acoustic interference that confuses the predator and makes it difficult for them to locate the moth. This jamming effect acts like an acoustic smokescreen.
Some sounds also function as warning signals. For instance, the audible squeak of the Death’s-head hawkmoth can deter predators. This sound may signal to a predator that the moth is unpalatable or dangerous, a form of acoustic aposematism. Additionally, sound production plays a role in intraspecific communication, such as courtship. Male moths of certain species produce quiet ultrasonic courtship songs to attract females, sometimes by rubbing specialized scales on their wings against their thorax. These low-intensity sounds are a strategy to avoid detection by predators or rivals.