Scientists have discovered more than 111,000 spiders living in a massive web, which appears to be the largest in the world, inside a permanently dark cave called the Sulphur Cave, on the Albania-Greece border. This extraordinary colony consists of a colossal web in a dark area of ??the cave, according to a study published Oct. 17 in the journal Subterranean Biology.
The web stretches 106 square meters along the wall of a narrow, low-ceilinged passageway, and is a tangle of thousands of individual, beam-shaped webs, the researchers say. It is the first evidence of colonial behavior by two common spider species and, according to the study's lead author, István Urák, an associate professor of biology at Sapientia University of Transylvania, Romania, it could represent the largest spider web in the world.
"The natural world still holds endless surprises for us," Urák told Live Science. "If I were to try to describe in words the emotion that filled me when I saw the web, I would emphasize admiration, respect, and gratitude. You have to experience it for yourself to truly understand."
The spider colony is located in the Sulphur Cave, a cave with a sulfuric acid pit formed by the oxidation of hydrogen sulfide in groundwater. Although the researchers discovered new data on this colony, they were not the first to see the giant web. Speleologists from the Czech Speleological Association discovered it in 2022 during an expedition to the Vromoner Canyon. A team of scientists visited the cave in 2024, collecting samples of the web, which Urák analyzed before setting off on his expedition.
His analysis showed that two species live in the huge colony: Tegenaria domestica, known as the house spider, and Prinerigone vagans. During the visit to the cave, Urák and his colleagues estimated that there were about 69,000 individuals of T. domestica and over 42,000 of P. vagans. DNA analyses confirmed that these are the dominant species in the giant colony.
The Sulphur Cave colony is one of the largest ever recorded, and the species involved were not previously known to coexist and cooperate in this way.
"It is a unique case where two species coexist within the same network structure in such large numbers," added Urák.
He stresses the importance of preserving the colony, despite the challenges that its location between two countries may pose. Meanwhile, researchers are working on another study that will reveal more details about the inhabitants of the Sulphur Cave.
