Spiders do not have ears, how do you hear?

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A new study – published in the Proceedings of the National Academy of Sciences “PNAS” (PNAS) on March 29 last – suggests that when the prey inside the spider’s web is in motion, enhancing those vibrations may be invaluable, as webs of the size of Sometimes 10 thousand times the size of the original spider.

In their experiments, the researchers used a group of “orb-weaver spiders” to conduct their experiments, and they are the most common group known to make large, spiral-shaped webs, often found in gardens, fields and woodlands. They made them produce spider webs inside rectangular frames in the lab, which could then be subjected to a series of tests.

The orbital spinner spider is the third largest of all spiders, and creates its webs in a modular fashion, then builds a frame of non-sticky silk even before the spider adds the new web. sound induced.

Perfect harmony with the sound

A laser vibrometer was used to measure spider web silk’s response to music in an anechoic (non-reflective) chamber, a chamber designed to absorb sound or electromagnetic waves completely and eliminate reflection and external noise. To pick up the sound when it arrives.

Sounds of different frequencies and from different directions were tested using the nets, and then related responses were obtained from the spiders; They usually tip over, bend, or flatten in response. In the case of directional sound, the spiders orient themselves towards the location where the sound is coming from.

Additional experiments with miniature speakers placed near the edge of the web showed that sounds traveled more through the webs than through the air, with some spiders responding to vibrations even when the sound did not reach the spiders through the air.

Hidden ear inside the spider’s body

The new study builds on previous research on the way spider webs interact with sound and music, but the way silk threads respond to sound waves is different from how the eardrums work.

Humans and most other vertebrate species have eardrums that convert sound wave pressure into electrical signals, which are then decoded in our brains. But insects and arthropods (including spiders) do not have this eardrum; So spider webs may be an alternative.

We know that spiders are able to hunt in groups, for example, via the vibrations of the web that pass through the sensory organs on the heel bone claws at the tips of the spider’s legs. In this case, they are clearly responding to something when they hit sound waves, but more research will be needed to find out how spiders process this information.

“There can even be an ear hidden inside the spider’s body that we don’t know about,” says mechanical engineer Junpeng Lai of Binghamton University in New York – in a university press release.

closer look

Through their movements in response to sounds, spiders may be tuning the strings of the web to pick up different sound frequencies, and there are plenty of potential avenues for researchers to explore based on this latest study, which includes potential improvements to audio equipment that could benefit from some natural inspiration.

And mechanical engineer Ron Miles – from the same university – says, “The spider is really natural evidence that this is a viable method for sensing sound by using viscous forces in the air on thin fibers,” and added, “If it works in nature, perhaps we should take a closer look at it.” .

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