As Dan Robitzki puts it, they “outsource” their hearing to the web (like the web was a microphone?):
The bridge spider uses its web as an engineered “external ear” up to 10,000 times the size of its body, according to a preprint study posted to bioRxiv on October 18. The discovery, which has not yet been peer reviewed, challenges many assumptions that scientists have held for years about how spiders and potentially other arthropods navigate and interact with the world around them.
“Evolutionarily speaking, spiders are just weird animals,” Jessica Petko, a Pennsylvania State University York biologist who didn’t work on the new study, writes in an email to The Scientist. “While it has been long known that spiders sense sound vibration with sensory hairs on their legs, this paper is the first to show that orb weaving spiders can amplify this sound by building specialized web structures.”
Spiders—both orb-weavers and others—are perfectly capable of hearing at closer distances without their webs thanks to the tiny hairs and organs on their legs that sense vibrations as air flows past. But the majority of spider biologists assumed that they could only hear sounds in their immediate vicinity, senior study author and Cornell University neurobiologist Ronald Hoy tells The Scientist.
Dan Robitzki, “Spider Uses Its Web Like a Giant Engineered Ear” at The Scientist (October 29, 2021)
If it weren’t for massive computers, one might be tempted to say there isn’t anything humans have invented that the design of some life form hasn’t embodied first.
The paper is open access.
You may also wish to read: In what ways are spiders intelligent? The ability to perform simple cognitive functions does not appear to depend on the vertebrate brain as such.