Spiders use their web like a speaker to boost their hearing, scientists have revealed.
Researchers found that orb-weaving spiders, made famous in the film Charlotte’s Web, actually use their webs to capture sounds as well as prey.
The team’s study, published in the journal Proceedings of the National Academy of Sciences, provides the first evidence that a spider can outsource hearing to its web.
Although it is well-known that spiders respond when something vibrates their web, the new study shows for the first time that spiders turned, crouched or flattened out in response to sounds in the air.
In a bid to revolutionize microphone technology Professor Ron Miles, from the Department of Mechanical Engineering at Binghamton University’s Thomas J. Watson College of Engineering and Applied Science, has been studying the issue for 30 years.
The findings have implications for designing extremely sensitive bio-inspired microphones for use in hearing aids and cell phones.
A single strand of spider silk is so thin and sensitive that it can detect the movement of vibrating air particles that make up a soundwave, which is different from how eardrums work.
Prof Miles, whose previous research has led to the invention of novel microphone designs based on hearing in insects, said: “The spider is really a natural demonstration that this is a viable way to sense sound using viscous forces in the air on thin fibers.
“If it works in nature, maybe we should have a closer look at it.”
Spiders can detect minuscule movements and vibrations through sensory organs on their tarsal claws at the tips of their legs, which they use to grasp their webs.
Orb-weaver spiders are known to make large webs, creating a kind of acoustic antennae with a sound-sensitive surface area that is up to 10,000 times greater than the spider itself.
The team used Binghamton University’s anechoic chamber, a completely soundproof room.
Collecting orb-weavers from windows around campus, they had the spiders spin a web inside a rectangular frame so they could position it where they wanted.
The team began by using pure tone sound three meters away at different sound levels to see if the spiders responded or not.
Surprisingly, they found spiders can respond to sound levels as low as 68 decibels, the level of a normal conversation. For louder sounds, they found even more types of behaviors.
The spiders can also tell the sound’s incoming direction with 100% accuracy.
To better understand the spider-hearing mechanism, the researchers used laser vibrometry and measured over one thousand locations on a natural spider web, with the spider sitting in the center.
The result showed that the web moves with sound almost at maximum physical efficiency across an ultra-wide frequency range.
Prof Miles continued: “Of course, the real question is, if the web is moving like that, does the spider hear using it? That’s a hard question to answer.”
Doctoral student Junpeng Lai said: “There could even be a hidden ear within the spider body that we don’t know about.”
By placing a mini speaker near the spider the team could work out that the sound was picked up along the web more than in the air, proving that spiders could use the web to hear.
The researchers also found that, by crouching and stretching, spiders may be changing the tension of the silk strands, thereby tuning them to pick up different frequencies.
By using this external structure to hear, the spider could be able to customize it to hear different sorts of sounds.
Mr. Lai admitted he was afraid of spiders when he began working on the project.
He said: “I’ve been afraid of spiders all my life, because of their alien looks and hairy legs.
“But the more I worked with spiders, the more amazing I found them. I’m really starting to appreciate them.”
