World's Biggest Spiderweb Spans Two Countries and Is Home to More Than 111,000 Spiders
If you thought the cobweb lurking in your garage was unsettling, researchers have found something on an entirely different scale — a spiderweb roughly half the size of a tennis court, hidden deep inside a cave on the border of Greece and Albania.
It’s here that a group of researchers uncovered what might be the world’s biggest spiderweb, measuring 106 square meters (1,140 square feet) and believed to house up to 111,000 spiders.
The research was published in the journal Subterranean Biology in October 2025.
A Spiderweb Hidden in Permanent Darkness
The massive web was first observed in 2021 by cavers from the Czech Speleological Society exploring the Vromoner Canyon, which straddles the border between Greece and Albania.
Inside a section known as the Sulfur Cave, located 50 meters (164 feet) from the cave entrance in a permanently dark passage, the explorers encountered the sprawling structure.
Marek Audy, who originally discovered the spiderweb, described it as “dense” and “like a blanket.”
“When there’s danger, the female crawls back and hides, and no creature of a higher order can dig her out of there,” Audy said.
The web stretches along a narrow, low-ceilinged passage and is made from a multi-layered patchwork of individual funnels that form a spongy mass.
Two Spider Species, One Unlikely Home
Upon closer examination, scientists discovered a few surprising facts about the spiders living inside the web.
First, the colony consists of two different species that don’t normally coexist peacefully: roughly 69,000 Tegenaria domestica (barn funnel weavers, commonly known as house spiders) and 42,000 Prinerigone vagans spiders.
Researchers estimated spider numbers by counting individual web funnels and collecting specimens for further analysis.
Since barn funnel weavers typically prey on the smaller Prinerigone vagans, their shared living arrangement is all the more remarkable (and mysterious).
So how are these natural enemies managing to live side by side?
Researchers believe the cave’s poor lighting impairs the spiders’ vision, creating an unlikely truce between the species.
They also think the never-ending food supply helps limit the hostility between species — especially since an estimated 2.4 million midge flies buzz around the Sulfur Cave spider colony.
Dr. Lena Grinsted, a senior lecturer at the U.K.’s University of Portsmouth who was not a part of the study, offered perspective on this unusual arrangement.
“Spiders, in general, are not particularly good at seeing stuff … and that includes these two species,” she told the Associated Press.
“So often if you have spiders in close vicinity, they will fight and end up eating each other,” said Dr. Grinsted. “We can sometimes see that if there’s an abundance of food that they sort of become a bit less aggressive.”
While the spiders likely work together in building the web, Grinsted added that it’s “highly unlikely that they cooperate in anything else like prey capture, in brood care, or looking after each other’s babies.”
A Spider Colony Cut Off From the Outside World
The second major finding involves the spiders’ DNA. Analysis showed the cave-dwelling spiders are genetically distinct from their surface-dwelling relatives — a discovery that surprised scientists.
“The DNA is interesting because they revealed that the species which live inside the cave is different from the one which lives outside the cave,” Dr. Blerina Vrenozi, a biologist and zoologist at the University of Tirana in Albania who co-authored the study, told the Associated Press.
“So it’s the same species, but different DNA,” she added.
Their sulfur-rich diet has significantly reduced the diversity of their gut microbiomes. Both findings suggest the colony does not mix with outside spider populations — instead, they’ve adapted exclusively to cave life.
Taken together, the discoveries paint a picture of a thriving underground world where tens of thousands of spiders have carved out an existence entirely separate from the world above, sustained by darkness and an endless buffet of flies.
This article was created by content specialists using various tools, including AI.
