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These Spiders Use Their Webs Like Huge Silky Ears

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Karen Hopkin: This is a 60-second flag from Scientific American. I’m Karen Hopkin.

Some things are so adorable, we’d say they’re as cute as an insect’s ear. Of course, insects do not have ears. But a new study shows that orb-weaving spiders can use their webs to detect sounds. The results were published in the Proceedings of the National Academy of Sciences.

Rum today: Any animal that makes sounds likely has an ear.

Hopkins: Ron Hoy studies neurobiology and behavior at Cornell University in Ithaca.

Hui: …from tiny crickets and flies that are even smaller than crickets, all the way to humans of course.

Ron Miles: It is also interesting that a large number of animals do not have an eardrum. But they still heard.

Hopkins: This is Ron Miles.

miles: The two Ron, here.

Hopkins: rune mileswho was collaborating with Ron Hui For 30 years, an engineer at Binghamton University …

miles: …an hour’s drive from Cornell.

Hopkins: Creatures that lack an eardrum receive the acoustic input of very fine hairs.

miles: If you look at spiders and insects, you will find that they are covered with hairs.

Hopkins: Since these tiny, fragile filaments can float freely in the breeze, they are great at sensing the air currents that make up sound waves.

miles: Since we learned that many animals like small insects and spiders have hair that can sense sound,…we were kind of wondering how you could make something that could feel the way some of these little animals do.

Hopkins: Possibility emerged during an afternoon outing.

miles: A graduate student, Jian Chu, was walking in a nature reserve on campus one day and noticed when the wind blew, if you looked at a spider web, it moved with the wind. He thought that perhaps a thin spider web or spider silk could act as a sound sensor.

Hopkins: To find out, the researchers persuaded a spider to give them a little silk …

miles: …and we played the sound on a small tuft of spider silk and found that when the silk is very thin, it moves with air in a sound field wonderfully…a wide range of frequencies, from 1 Hz to 50 kHz. So we knew then that spider silk was kind of a perfect, perfect sound sensor.

Hopkins: It was an eye-opener for researchers…but does it ring spiders’ ears?

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miles: So we set out to try to find out if spiders were actually able to hear sound using their web. This was a difficult question to answer.

Hopkins: For one thing, they had to find a way to insert an entire mesh into a special soundproofed room in the basement of the laboratory building.

miles: As you know, spider webs are very sensitive. You can’t go out in the woods and find a spider web and take it home. It is related to things. And it is not easy to keep them intact.

Hopkins: Especially the ones made by orb weavers…spiders like the title character in Charlotte’s Web.

Hui: We are talking about a very cool network. It’s a wheel-shaped net that’s around upstate New York…if you walk into any field, you either walk across it or you’ll see it and avoid it because it’s big. Its width can be up to a yard or a meter.

Hopkins: So Jian Zhou and fellow student Jun Bing Lai came up with a way to get on-demand networks.

miles: What they did was make a little wooden frame… kind of the right picture frame size… and they put this frame on the windows of our building.

Hopkins: The lights in the building attract insects…and insects attract spiders.

miles: So… spiders built their webs on tires. Then in the morning my students would go and collect the tires and snatch the spiders and take them and put the tire in…the room is intact.

Hopkins: Now, how do you know if a web works as a spider hearing aid? One way is to observe a spider’s brain.

Hui: My lab, the neurophysiologists, made some recordings from the sensory system of the nervous system that actually showed that you get an acoustic response in the nerves to the sound … coming from a speaker just over a meter away.

Hopkins: But what was most obvious was how the spiders behaved.

Hui: For very loud sounds, you can get a strong response…the spider will either flatten out or it may actually bend. But it really does wander. This is a sign [to a biologist] alarm response.

Hopkins: And when you sing with voices that are maybe 10 decibels or 100 times weaker…

Hui: Without changing body position or making any other movements, he may simply lift his front legs off the web.

Hopkins: Leg stretching, Howe says…

Hui: …is the spider’s way of possibly putting in two more sensors to see what’s coming. We don’t know that yet. But this response to a very soft stimulus may just be the spider’s reaction to “I know something is in there, I heard it, but I need more information.” So… this is the demo that was needed to show that spiders can hear sounds.

Hopkins: This stringent approach to acoustics could one day change the way we make microphones…and take them Online broadcasting to a whole new level.

For 60 Second Science from Scientific American, I’m Karen Hopkin.

[The above text is a transcript of this podcast.]

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