Recently, an international team of European scientists discovered the world's largest spider web structure in a dark sulfur cave on the border of Albania and Greece. It is reported that this giant spider web covers an area of more than 100 square meters, like a living curtain, and is home to about 110,000 spiders. The discovery is considered a "nightmare" for those who fear spiders.
The research team first saw this multi-layered spider web during a wildlife survey in 2022. Approximately 69,000 Tegenaria domestica and 42,000 Prinerigone vagans live together in the web. This is the first time that these two spiders have been observed building a nest together, and it is also the first time that collective spider web phenomena have been recorded in chemoautotrophic caves.
The Sulfur Cave has an ecosystem based on chemoautotrophy, which does not rely on sunlight but converts chemical energy into organic matter through sulfur-oxidizing bacteria. These bacteria coat rock and sediment surfaces and are eaten by small invertebrates such as chironomid larvae and woodlice, which in turn become prey for large burrowing insects such as spiders, beetles and centipedes. The cave's water temperature is about 26°C all year round, is rich in hydrogen sulfide, and exudes a pungent smell of rotten eggs, bringing a unique life support system.
In the cave, these spiders coexist peacefully, with thousands of funnel webs merging to form multi-layered structures spread across the cave walls, without the usual aggressive cannibalism. Even more surprising is that thin-web spiders, which are usually prey, also live safely inside giant spider webs.
The aerial chironomids in the cave are extremely dense, with about 45,000 per square meter. Their larvae feed on bacterial biofilms, providing abundant food for spiders, completely eliminating hunger and resource competition. The analysis showed that the carbon and nitrogen in the spider's body came from sulfur-oxidizing bacteria rather than ground plants.
Further genetic testing found that the spider population in the sulfur cave has unique DNA, which is different from the population outside the cave, showing long-term isolated evolution, and the microbiome is also more homogeneous. The study also found that cave spiders lay significantly less eggs than ground spiders, which may be limited by the high energy demands of dark, low-oxygen environments and the lack of natural predators.
Scientists say this study reveals the voluntary colony behavior of spiders under sufficient resources and provides new insights into the adaptation and evolution mechanisms of surface species in hydrogen sulfide caves. Sulfur caves not only allow us to understand how life evolves and adapts in extreme environments, but also shows how common spiders on the surface rely on cooperation to reproduce and survive in harsh ecosystems.
The research was published in the journal Underground Biology.