Spiders, often perceived as silent inhabitants of our world, actually engage in a complex acoustic landscape. While they lack vocal cords, many spider species produce a variety of sounds, though these are frequently imperceptible to human ears. Their methods of sound creation and perception offer fascinating insights into their communication and survival strategies.
How Spiders Produce Sounds
Spiders employ diverse physical mechanisms to generate sounds. One common method is stridulation, which involves rubbing specialized body parts together, similar to how crickets produce sound. Many tarantulas, for instance, create a hissing or rustling noise by rubbing bristles on their legs against other leg segments, their pedipalps, or even parts of their carapace, often as a defensive display. Wolf spiders also use stridulation, sometimes described as a “purring” or “chirping” sound.
Another sound-making technique is drumming or tapping. Spiders use their pedipalps or legs to tap rhythmically on surfaces like the ground or leaves. Jumping spiders are notable for this behavior, creating distinct thumps and buzzes during their elaborate displays. Some spiders also generate vibrations or buzzing through rapid body movements or by rubbing silk. The male Buzzing Spider, for example, vibrates its abdomen against a leaf to attract females.
The Purpose of Spider Sounds
Spider sounds serve several important communicative functions, particularly in social interactions. During courtship, male spiders frequently use sounds to attract females and signal their presence. Male jumping spiders, for instance, incorporate thumps, scrapes, and buzzes into their courtship dances. Male wolf spiders also produce “purring” vibrations as part of their rituals to potential mates.
Sounds are also used for territorial defense and warning. Spiders may produce noises to deter rivals or warn off predators. Some Australian tarantulas, sometimes called “barking” or “whistling” spiders, are known to make distinct sounds when threatened. Certain spiders, such as Palpimanus spiders, produce a buzzing sound by rubbing their front appendages against their mouthparts when disturbed, mimicking wasps to deter predators.
Beyond Audibility: How Spiders “Hear” Vibrations
While spiders produce sounds, their primary mode of “hearing” is through the detection of vibrations rather than airborne sound waves. They possess specialized sensory organs that are highly sensitive to even minute movements. This distinction helps explain why most spider sounds are not audible to humans.
Spiders use two main types of mechanoreceptors. Trichobothria are elongated hairs on their legs and pedipalps, extremely sensitive to airborne vibrations and air currents. These hairs can detect the slightest air movement, enabling spiders to sense nearby prey or predators.
Additionally, spiders have slit sensilla, small grooves or slits in their exoskeleton, particularly on their legs. These sensilla deform in response to physical strain and substrate vibrations, allowing spiders to interpret movements within their environment, such as those from an insect caught in their web. This sensory system allows spiders to perceive a world rich in vibrational information.