Many people associate summer evening sounds with insect “chirping,” often attributing these calls to grasshoppers. However, insect sounds are more diverse and complex than a single chirp. These acoustic signals serve distinct purposes, guiding behaviors vital for survival and reproduction. This article clarifies common misconceptions about insect sound production.
Grasshoppers: Sound Makers, Not Chirpers
Grasshoppers do not produce the classic “chirping” sound. Instead, they create distinct noises through various mechanisms. One primary method is stridulation, where a grasshopper rubs its hind legs against its forewings, generating a rasping or scratching sound.
Another sound production method, particularly observed in band-winged grasshoppers, is called crepitation. This involves the insect snapping its hind wings rapidly during flight, which produces a crackling or loud clicking noise. While both male and female grasshoppers can make sounds, males are generally more vocal.
Meet the True Chirpers
The familiar “chirping” sound is primarily produced by crickets and katydids. These insects use stridulation, but their method differs from grasshoppers. Crickets and katydids create sounds by rubbing specialized structures on their forewings together. One wing has a file-like ridge with teeth, and the other has a sharp edge or scraper; when these are rubbed against each other, the wings vibrate, amplifying the sound.
Male crickets are the primary sound producers, using their rhythmic chirps to attract females and to establish and defend their territories. The pattern and frequency of these chirps can vary significantly between species, acting as a species-specific calling song. Katydids, closely related to crickets, produce sounds that can range from buzzing or ticking to the distinctive “Katy did!” sound, which gave them their name. In some katydid species, both males and females are capable of stridulating.
The Purpose and Mechanism of Insect Sounds
Insect sounds serve a variety of important biological functions, extending beyond simple communication. A primary purpose is mate attraction, where males often produce specific calls to signal their presence and species identity to receptive females. These acoustic signals also play a role in territorial defense, warning competing males or other insects to stay away from an occupied area. Some insects also produce sounds as a defensive mechanism, such as startling predators or signaling their toxicity.
Insects employ several sophisticated mechanisms to generate these sounds. Stridulation, the rubbing of two body parts together (a file and a scraper), is the most common method, used by grasshoppers, crickets, and katydids. Another mechanism involves tymbal organs, which are ribbed membranes that buckle rapidly when muscles contract, producing clicks that combine into a buzzing or rattling sound, as seen in cicadas. Other methods include the vibration of wings or body parts during flight, like the buzz of bees, and even percussion, where insects tap body parts against a surface. The efficiency of these sound productions is often enhanced by resonant structures, such as body cavities or burrows, which amplify the signals.