What scientists are learning from the strangest spider webs on Earth
Webs can be decorated with decoys, fine-tuned like guitars—and hold secrets about evolution.
In a narrow passage deep inside an underground cavern between Albania and Greece, scientists pushed through waist-deep black water and clung to ropes to make a startling discovery. In the beams of their flashlights lay a sparkling wall of webs, stretching as far as they could see. The webs belonged to more than 110,000 spiders, from two species, working together to create a structure spanning 1,140 square feet.
At times, the mat of the web was so heavy it was falling down in places. Perhaps the web had become so large because the cave was so remote and so protected. This glistening metropolis of spiders in the Sulfur Cave is fed by a constant supply of small flies called midges. The researchers described the scene in a recent publication, calling it “an extraordinary colonial spider community.”
The unusual find is just one recent development in the weird world of webs. Spiders use their webs to catch prey, but also cover eggs, transmit vibrations and pheromone signals, and create glue to retain their catches.
These sticky structures have fascinated humans for centuries—the ancient Greeks and Romans used webs as bandages for human wounds. But just in the past few months, scientists have documented startling new structures and behaviors. From spiders that decorate to those that create giant decoys of themselves, scientists are still uncovering the awe-inspiring magic of spider webs.
“The evolution of silk is one of the most amazing things that has happened in the history of life,” says Cheryl Hayashi, a biologist with the American Museum of Natural History in New York. It didn’t just happen once, says points out—silk is not just a fix-all like duct tape. Instead, it’s a substance that continues to change. “Spiders keep diversifying their use of silk—and keep finding new ways to use it.”
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Artistic arachnids
A web can act almost as an extra organ for spiders, says Gabriele Greco, a postdoctoral researcher at University of Pavia, in Italy. Biologically speaking, webs are defined as an “extended phenotype,” meaning that the web is an external part that the spider produces that is evidence of its genome. It’s more “like having an extra hair or an extra arm,” Greco says—as if your house served as an extension of your own body.
That extra limb can provide a lot of benefits. A 2022 study demonstrated that orb-weaving spiders use their webs as an extended ear to sense vibrations, increasing their sensory area by up to 10,000 times. The web is like a giant acoustic antenna, capturing movements in the air and sending them to the spider.
But we are still just beginning to understand the true scope of spider web ingenuity and complexity. For example, scientists had long wondered why spider webs have extra decorations like zig-zag threads in them. Greco recently published research in the journal PLOS One showing that these artistic touches—known as stabilimenta—can influence the web propagation of vibrations when prey gets stuck on the sticky threads. But there is a tradeoff for spiders—adding decoration adds mass to the web, and the debate hasn’t been settled. “Nobody knows exactly why spiders decorate their webs,” Greco says.
The chemical composition of silk, which includes more than 2,200 proteins, is an active area of research. In one recent experiment, Greco fed nanomaterials like carbon nanotubes to spiders, which then produced naturally reinforced silk. He is also using artificial intelligence and machine learning to better understand the structure and function of webs.
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Decoys for days
When Larry Reeves was walking around a jungle in the Philippines, something caught his eye: a spider he didn’t recognize in a web. Reeves looked closer, and to his surprise, he realized it wasn’t a spider at all—instead, it was a large spider shape using silk and plant matter woven into the web. “That was the first inkling,” he says, “that this could be something novel.”
Reeves attended a presentation at a conference by another researcher, Phil Torres, who described a spider in Peru that also built spider-like shapes in their webs. It was so serendipitous that the two decided to team up on the study, along with a few other colleagues. The group has now published new research on the fake spiders in cyclosa webs, which are crafted from silk, plant debris and parts of prey. Some decoys look rudimentary, but others accurately reflect the form of a spider, as they write in a study published recently in the journal Ecology and Evolution.
The reason for the large decoys, the researchers surmise, is anti-predator defense. The decoys appear to be much larger than the half-inch spiders that live in the webs, so any predators that use sight to hunt would be warned off. “They’ll notice a larger spider there that probably is not on their menu, and they'll kind of avoid the web because they see a larger spider there that's kind of outside of the range of what they would want to feed on,” explains Reese.
Future experiments could test different strategies the spiders employ to build the decoys. Still, scientists have a sense of awe at what the spiders are able to construct, using materials around them. “There are only four known species at this time that can build a bigger structure of themselves from scratch,” says Torres. “Three of those are these spiders. The other one is humans.”
The artistry and engineering of webs will continue to amaze us, as spiders keep spinning out new scientific findings. For Hayashi, the cave spiders in Albania show how a spider’s web interacts with its surroundings—modifying it based on their environment, their size and even the nutrition that is available to them. “If you’re a painter and you know how to paint a particular picture, if you have a different canvas you can adapt to that,” she says. In the same way, spiders use what’s available to spin a web.”
