The familiar chirping of crickets is a common sound, especially as evening descends and ambient noise fades. This rhythmic chorus often marks the transition from day to night. While these sounds are widely recognized, the biological processes and environmental factors contributing to their perceived loudness are not always clear. This article explores how crickets make sound, the purposes their calls serve, and why they seem so pronounced at night.
How Crickets Make Sound
Crickets produce their distinctive sounds through stridulation, which involves rubbing specialized body parts together. This sound production is primarily carried out by male crickets, who possess a “file and scraper” system on their forewings.
One wing has a row of bumps, similar to the teeth of a comb, known as the file. The other wing has a hardened edge, called the scraper. When a male cricket chirps, it elevates its wings and rapidly rubs the scraper of one wing across the file of the other. This rapid movement causes vibrations, and thin, papery portions of the wings amplify the sound.
The Reasons Behind the Racket
The sounds produced by male crickets serve as a complex form of communication within their species. Their primary reason for chirping is to attract mates. These “calling songs” are specific to each cricket species, allowing females to identify potential partners.
Male crickets also use chirps for territorial purposes, warning off rival males from their claimed spaces. If another male approaches, the resident male might alter its chirp to a more aggressive “rivalry song” to deter the intruder. Some species also produce “alarm calls” when sensing a threat.
Why They Seem So Loud
Several factors contribute to crickets seeming particularly loud, especially after sunset. Crickets are primarily nocturnal, active at night when darkness offers them protection from predators. This nocturnal activity aligns with a generally quieter environment, as much of the daytime ambient noise diminishes. This reduction in background noise allows cricket chirps to be heard more distinctly and over greater distances.
The rate at which crickets chirp is directly influenced by temperature; warmer temperatures lead to faster and more frequent chirps. This is because crickets are cold-blooded, and their metabolic rate, which drives their muscle contractions for chirping, increases with heat. Consequently, on warm summer nights, their accelerated chirping can make them seem more incessant and louder. Sound also travels more effectively at night due to atmospheric conditions. Additionally, some crickets can amplify their calls by using the ground as a resonator.