Live Science goes into the brimstone of the underworld — a sulfuric cave literally named “Sulfur Cave” — on the border of Greece and Albania, and finds — along with a biologist from Transylvania — the lightless pit is filled with the largest spiderweb ever discovered:
The web stretches 1,140 square feet (106 square meters) along the wall of a narrow, low-ceilinged passage near the entrance of the cave. It is a patchwork of thousands of individual, funnel-shaped webs, the researchers noted.
This is the first evidence of colonial behavior in two common spider species and likely represents the largest spiderweb in the world, said study lead author István Urák, an associate professor of biology at Sapientia Hungarian University of Transylvania in Romania.
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The spider megacity is located in Sulfur Cave, a cavern that was hollowed out by sulfuric acid formed from the oxidation of hydrogen sulfide in groundwater. While the researchers revealed tantalizing new information about Sulfur Cave’s spider colony, they weren’t the first to see the giant web. Cavers with the Czech Speleological Society discovered it in 2022 during an expedition in the Vromoner Canyon. A team of scientists then visited the cave in 2024, plucking specimens from the web that Urák analyzed before going on his own expedition to Sulfur Cave.
This analysis revealed that two spider species live in the colony: Tegenaria domestica, known as the barn funnel weaver or domestic house spider, and Prinerigone vagans. On their visit to the cave, Urák and his colleagues estimated there were about 69,000 T. domestica and more than 42,000 P. vagans specimens.
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You can read more of Urák’s research here, in Subterranean Biology.