Locusts are known for transforming from solitary individuals into vast, destructive swarms that impact agriculture. Beyond their visual spectacle, locusts produce acoustic signals. These signals influence individual interactions and the coordination of their massive collective movements.
Sound Production Mechanisms
Locusts create sound through two distinct methods: stridulation and crepitation. Stridulation involves rubbing one body part against another, similar to playing a violin. Many species rub spikes on their hind legs against their front wings, producing a buzzing sound. This action generates vibrations, amplified by thin, rigid parts of their wings.
Crepitation is the crackling or snapping sound made by their wings during flight. This occurs when wing membranes become stretched and rigid as they fly. Some species, like band-winged grasshoppers, produce a loud snapping sound during daytime flights. The exact sound produced can vary between different groups of locusts, depending on the specific body parts and mechanisms involved.
Purposes of Locust Sounds
Locusts use their sounds for communication. Males often produce specific calls to attract females, frequently using stridulation as a courtship call. Different species may have unique auditory signals, making sound a reliable indicator for identification.
Beyond reproduction, sounds also play a role in territorial defense. Locusts use stridulation to warn other individuals away from their occupied areas. This acoustic signaling helps establish boundaries and reduce conflict over resources or space. Additionally, locusts produce alarm calls to signal danger to nearby individuals. These sounds alert others to potential threats, promoting evasive action. The sounds contribute to regulating various locust behaviors.
Role of Sound in Swarm Coordination
Sound contributes to the dynamics of locust swarms, influencing their collective movement and cohesion. While not as overtly synchronized as a coordinated chorus, the sounds produced by numerous individuals within a swarm can collectively affect the group’s behavior. The continuous buzzing, clicking, or crackling from thousands or millions of locusts during mass flights or marching bands create an ambient acoustic environment. This collective sound, though not necessarily a directed signal, might contribute to maintaining the density and direction of the swarm.
Research suggests that “noise” or randomness within a swarm can facilitate coherence in collective motion. Experiments investigating marching bands of locust nymphs have shown that individual locusts may increase the randomness of their movements if the group loses alignment. This implies that the overall acoustic environment, a byproduct of individual movements and interactions, could provide cues that help prevent the swarm from dispersing. While specific “swarm coordination sounds” are not identified, the constant soundscape generated by the multitude of insects likely plays an indirect role in sustaining the integrity and direction of these massive biological phenomena.