Spiders Are Creeps!
Some arachnids use their webs to listen to us and other things. The hair-raising discovery may lead to exciting new tech, but you best keep your voice down.
Do you ever get the spooky sense that someone is listening in? Well, if there is a spider hanging in your window, you could be on to something. Researchers have discovered these tiny voyeurs may be using their webs to eavesdrop on us.
A study out of Binghamton University shows how some spiders use their webs as a kind of microphone. Orb-shaped webs, like the ones used as Halloween decorations, vibrate perfectly with the surrounding air. A spider's super-sensitive legs translate that vibration into the perception of sound. The web’s silk acts like a resonant sensor, sending information about volume, pitch, and even orientation. This adds to the spider's already scary set of surveillance skills, including its eight eyes! The discovery could lead to amazing new audio technologies for humans as well.
"My interest for quite some time has been on how to sense sound and how animals and people detect it," said Ron Miles, distinguished professor at Binghamton and senior author of the study. Miles usually researches acoustics. He shared what got him thinking about the eight-legged creatures. "Spiders are incredibly good at detecting the motion of their web,” he thought. “Maybe that's a way for the spider to hear?" His team used directional speakers in their lab to show how the they reacted to sound as quiet as a human voice, around 68 dB. The spiders recoiled, lifting their legs, sometimes retreating in response.
The team used bridge spiders, a common orb-weaver often found nesting in the protected wetlands near the university. Like many orb-weavers, they do not have ears like we do. Finely tuned hairs on their body, called sensilla, help them pick up slight vibrations in the air. Their eyes aren't as refined as some spiders, who use their vision to hunt. A web that enhances sound perception could provide a clear advantage. The spiders are able to listen to the immediate soundscape, detecting potential predators or prey close to their web.
Dinesh Rao, a spider researcher who runs Rao Spider Lab outside of Mexico City, described how they sense their environment, "They live in a sonic landscape. Their world is sound and that is probably as important to them as vision and light is to us." Dinesh's own research focuses on jumping spiders. He has also shown their ability to hear. "When you play the frequency of wasp wings, they freeze in place, so they can clearly recognize the sound of one of their predators." Jumping spiders don't make webs to trap prey, instead they rely on their superior eyesight to hunt. "They can actually interact with you, like your pointer fingers, it will react to your motion and look at you, like a little cat," said Rao.
Spiders are known to exhibit other creepy behaviors. Some mimic the motion of their predators to blend in and avoid being eaten — very sneaky. Others use fireflies trapped in their webs to signal and lure in their friends — psychopaths! Kleptoparasite spiders stealthily invade the nests of larger spiders, snatching some of their dinner. But the observation that spiders use their webs to listen in may mean they have a partner in crime: their silk.
As the Binghamton team looked deeper into spider silk acoustics, they discovered that it performed extraordinarily well. Silk seemed to resonate perfectly with the air, acting like a violin string being plucked in reverse. "If you take a single strand of spider silk and play sound, it responds beautifully," said Miles. "The silk has got great frequency response."
Miles and others are interested in the potential use of silk to detect a variety of frequencies that traditional microphones can't catch. In theory, the silk-inspired microphones could detect frequencies well below human hearing. Miles envisions detectors that pick-up the low hum of an approaching tornado or track explosions in a war zone, due to silk’s ability to locate directional orientation. A silk-based detector in your phone could alert you to evacuate to a safer location before a standard alert could.
Despite the potential for new science, research into orb-weavers and other spiders have confirmed the truly terrifying: the spiders are indeed listening — and they’re doing it in interesting and novel ways. Like us, they may be curious creatures. I asked Miles if he thought we should be careful of what we say around these little weirdos. He put things into perspective."They might be listening, but they can't hurt you." Most spiders are beneficial and as scientists study them more, they’re discovering new materials and ways of perceiving the world. Miles predicts breakthrough science as a result of further research, "It's a really unexplored field."
References and Citations:
Miles, R. (2024, October 3). Phone interview. Binghamton University.
Rao, D. (2024, October 3). Video interview. Universidad Veracruzana.
Zhou, J., Lai, J., Menda, G., Stafstrom, J. A., Miles, C. I., Hoy, R. H., & Miles, R. N. (2022). Outsourced hearing in an orb-weaving spider that uses its web as an auditory sensor. Proceedings of the National Academy of Sciences USA, 119(31). https://doi.org/10.1073/pnas.2122789119
Zhou, J., & Miles, R. N. (2017). Sensing fluctuating airflow with spider silk. Proceedings of the National Academy of Sciences USA, 114(33). https://doi.org/10.1073/pnas.1710559114
Rosales-García, R., Tapia-McClung, H., Narendra, A., & Rao, D. (2021). Many paths, one destination: Mapping the movements of a kleptoparasitic spider on the host’s web. Journal of Comparative Physiology A, 207, 1-9. https://doi.org/10.1007/s00359-021-01477-3
Subramaniam, N., Tamma, K., & Uma, D. (2023). An arachnid’s guide to being an ant: Morphological and behavioral mimicry in ant-mimicking spiders. Behavioral Ecology, 34(1), 99-107. https://doi.org/10.1093/beheco/arac104
Fu, X., Yu, L., Zhou, W., Lei, C., Jackson, R. R., Kuntner, M., Huang, Q., Zhang, S., & Li, D. (2024). Spiders manipulate and exploit bioluminescent signals of fireflies. Current Biology, 34(16), R768-R769. https://doi.org/10.1016/j.cub.2023.09.001
Ron Miles, Distinguished Professor Binghamton University. https://www.binghamton.edu/mechanical-engineering/people/profile.html?id=miles
Rao Spider Lab. Inbioteca, Universidad, Veracruzana, Mexico. https://raospiderlab.org
Hesselberg T, Gálvez D. Spider Ecology and Behaviour-Spiders as Model Organisms. Insects. 2023 Mar 28;14(4):330. https://pmc.ncbi.nlm.nih.gov/articles/PMC10143103/