Researchers discovered the world’s largest known communal spiderweb — over 100 m² — inside a sulfuric cave on the Greece–Albania border, hosting roughly 110,000 spiders from multiple species. The colony is dominated by Tegenaria domestica (~69,100) and Prinerigone vagans (~42,400) and is sustained by an estimated 2,414,440 non-biting midges in a chemoautotrophic ecosystem. A 2024 survey recorded 30 invertebrate species, and a 2025 genetic study found the cave spiders are genetically distinct from nearby surface populations.
World’s Largest Known Spiderweb Found in Sulfur Cave — 110,000 Spiders Build an Underground 'Citadel'
Researchers discovered the world’s largest known communal spiderweb — over 100 m² — inside a sulfuric cave on the Greece–Albania border, hosting roughly 110,000 spiders from multiple species. The colony is dominated by Tegenaria domestica (~69,100) and Prinerigone vagans (~42,400) and is sustained by an estimated 2,414,440 non-biting midges in a chemoautotrophic ecosystem. A 2024 survey recorded 30 invertebrate species, and a 2025 genetic study found the cave spiders are genetically distinct from nearby surface populations.
06:26, 07.11.2025Science
World’s Largest Known Spiderweb Discovered in a Sulfuric Cave
A recent study documents an extraordinary subterranean community: a communal spiderweb that covers more than 100 square meters inside a sulfuric cave on the Greece–Albania border. The web begins about 50 meters from the cave entrance, where conditions are permanently dark, the passage is narrow and low, and the floor is crossed by a sulfur-rich stream.
In places the accumulated silk and the mass of spiders have become so heavy that sections of web have detached from the rock face. Despite the dramatic setting, the spiders are not unusually large; multiple species have contributed to the structure, cooperating across generations to create what researchers describe as a spider "citadel."
The largest group in the colony is the Domestic House Spider, Tegenaria domestica, with an estimated ~69,100 individuals. Their main collaborators are roughly 42,400 Prinerigone vagans, a smaller species. The research team suggests permanent darkness suppresses some predatory reactions, allowing these species to coexist; P. vagans had not previously been recorded forming dense colonies.
Across the communal web the density ranges from several hundred to a few thousand spiders per square meter, totaling about 110,000 spiders. The colony is supported by an enormous prey base: the authors estimate more than 200 small chironomid midges per spider, roughly 2,414,440 individuals of the non-biting midge Tanytarsus albisutus.
These midges hover and breed above the sulfuric stream that runs along the cave floor. The environment supports a chemoautotrophic ecosystem in which microbes convert inorganic sulfur into energy-rich biofilm. Larvae feed on that biofilm, develop into insects (such as the midges), and in turn sustain the predatory spiders.
In 2024, a team from the Emil Racovitza Institute of Speleology explored Sulfur Cave after reports of unusually high animal abundance and documented 30 invertebrate species living in this self-sustaining system. In a 2025 follow-up study, lead author Istvan Urak and colleagues genetically sequenced the cave populations of P. vagans and T. domestica and found them genetically distinct from nearby above-ground populations, suggesting evolutionary divergence associated with the subterranean lifestyle.
Significance: This discovery illustrates how chemoautotrophic, lightless habitats can support dense, multi-species animal communities and promote genetic divergence in species commonly found on the surface.