While the idea of a spider letting out a terrifying scream is popular in fiction, spiders cannot vocalize like mammals. They lack the necessary biological equipment to produce sound by expelling air. However, they are not silent creatures; many species communicate through a complex system of vibrations and mechanical noises. These sounds serve specific functions for communication, courtship, and defense.
The Anatomy of Silence
Spiders cannot vocalize like humans or other vertebrates because their anatomy is fundamentally different. Mammalian vocal sound production relies on a larynx, or voice box, and a diaphragm that forces air over vocal cords. Spiders possess none of these structures, making true airborne sound production through vocalization impossible.
A spider’s respiratory system is not designed for vocal air expulsion, as they breathe using passive systems like book lungs or tracheae. They lack the muscular diaphragm needed to forcefully push air out to generate a loud, sustained vibration. Instead of vocalizing, spiders rely on a different sensory modality, primarily vibrations and touch. They perceive signals largely through specialized, highly sensitive hairs on their legs, called setae, which detect airborne and substrate vibrations.
Producing Sound Without Vocal Cords
Since spiders cannot vocalize, they generate noise through mechanical actions, primarily stridulation and percussion. Stridulation involves rubbing two specialized body parts together, much like drawing a bow across a violin string. This mechanism typically uses a structure with ridges or nodules, known as the plectrum, which is scraped across a finely ridged surface called the pars stridens. Many tarantulas, for instance, use stridulation by rubbing bristles on their legs or mouthparts together to produce a distinct hissing or buzzing sound. The specific location of these stridulatory organs varies among species, such as between leg one and two or on the chelicerae, producing different sound textures.
The second major method is percussion, where the spider taps, drums, or vibrates its body parts against a surface, such as the ground or a leaf. Male wolf spiders, like Schizocosa stridulans, are known for complex courtship displays that involve drumming their forelegs on the substrate, creating seismic signals that travel through the ground.
Sounds of Defense and Courtship
The sounds spiders create are almost always tied to two specific behavioral contexts: defense and courtship. Defensive sounds are typically loud enough to be heard by humans and often serve as a warning display to potential predators. When disturbed, certain tarantulas like the Goliath tarantula, Theraphosa blondi, will stridulate loudly, creating a hissing noise designed to startle or deter an aggressor.
In the context of mating, the sounds are often much quieter, operating as complex communication signals between a male and female of the same species. Male spiders use specific patterns of drumming, tapping, or vibrating their abdomens, known as tremulation, to signal their presence and species identity to a female. For example, the “purring” wolf spider, Gladicosa gulosa, creates vibrations and airborne sounds by dragging a special organ across a surface like a dead leaf, which the female detects as a mating signal. These intricate vibratory “songs” are a form of sexual selection, where females choose mates based on the complexity and vigor of the male’s acoustic performance.