Crickets are known for their distinct chirping, often heard on warm evenings. However, they do not always make noise, producing sounds only under specific circumstances and through particular biological mechanisms.
The Mechanics of Chirping
Crickets generate their characteristic sounds through stridulation, rubbing two specialized forewing parts together. Male crickets possess forewings with a hardened edge called a scraper on one wing and a file (a series of ridges) on the other. Rapid wing movement causes the scraper to slide across the file, creating vibrations that produce sound.
Each scrape creates a single sound pulse; a sequence of these pulses forms a chirp. Chirp frequency and quality depend on factors like the number of teeth struck per second and wing resonance. The forewings also contain a membrane called the harp, which vibrates and amplifies the sound, allowing it to travel farther.
Why Crickets Chirp
Crickets chirp primarily for communication, playing crucial roles in their social and reproductive lives. Male crickets produce various songs to attract mates and establish territory. The loud “calling song” draws in females from a distance and signals occupied areas to other males.
When a female approaches, the male switches to a softer “courtship song” to encourage mating. “Aggressive songs” or “rivalry songs” warn off competing males. These chirping patterns are unique to each cricket species, allowing females to identify potential mates of their own kind.
When Crickets Go Silent
Crickets do not always make noise; several factors influence their chirping. Only male crickets possess the specialized wing structures for stridulation, so female crickets do not chirp. Young crickets, or nymphs, also remain silent because their wings are undeveloped.
Temperature significantly affects cricket chirping. As cold-blooded insects, their metabolic rate is directly affected by ambient temperature. In colder conditions, crickets chirp less frequently or cease entirely due to slower muscle contractions. Warmer temperatures lead to more rapid chirping, and the chirp rate can even approximate the temperature.
Some cricket species are naturally silent or produce sounds in ways other than typical stridulation. For instance, Zebragryllus aphonus from the Amazon lacks the ridges needed for sound production, making it a silent cricket. Crickets also stop chirping if they detect a predator, as their chirps can reveal their location. They are sensitive to vibrations and noise, and will quiet themselves as a defensive mechanism to avoid being found.