You’d probably never notice a jumping spider across your living room, but it would surely notice you. The arachnids are known for their brilliant eyesight, and a new study shows they have even greater sensory prowess than we thought: Jumping spiders can hear sounds even though they don’t have ears—or even eardrums. To find this out, researchers implanted tiny electrodes in a region of spiders’ brains that would show whether sound was being processed. Then they placed the spiders on a specially designed box to eliminate any vibrations from below—most spiders sense their surroundings through vibrations—and scared the heck out of them with a speaker-produced buzz of one of their predators, the mud dauber wasp. An out-of-earshot, high-frequency buzz and a silent control elicited no response from the spiders. But the 80-hertz wasp buzz made them freeze and look around, startled, just as they would do in the wild. What’s more, data from the electrodes showed a spike in brain activity with each buzz, revealing that spiders actually hear sounds, from a swooping mud dauber wasp to you crunching potato chips on your couch. The researchers, who publish their work today in Current Biology, say further study is needed to see exactly how spiders receive sounds without eardrums, but they believe sensitive hairs on their legs play a part.
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