European Scientists Discover World's Largest Spider Web Housing 110,000 Arachnids in Toxic Cave
- MM24 News Desk
- 11h
- 2 min read
European researchers have uncovered the world's largest communal spider web deep within a toxic cave on the Albania-Greece border—a massive 100 square meters (1,000 sq ft) silk structure housing approximately 110,000 spiders thriving in complete darkness. The discovery, made during a 2022 wildlife survey, reveals two spider species living cooperatively for the first time in a unique ecosystem powered not by sunlight but by chemical energy.
An international team including scientists from the Czech Speleological Society found the web in what's known as Sulfur Cave, a chemoautotrophic environment sustained by sulfur-oxidizing bacteria. The researchers identified about 69,000 Tegenaria domestica (common house spiders) and 42,000 Prinerigone vagans spiders coexisting peacefully in the massive, multilayered web that resembles a living curtain. This marks the first recorded instance of colonial web-building in such an environment, reported the research team.
What makes this discovery particularly remarkable is the behavioral shift in these normally solitary and aggressive species. Above ground, T. domestica are solitary hunters that would typically prey on the smaller P. vagans. However, in this cave environment, both species live side-by-side without evidence of cannibalism or aggression. The secret to their peaceful coexistence appears to be an abundant food source: the air near the cave's warm, toxic stream is packed with Tanytarsus albisutus midges at densities of 45,000 per square meter.
The entire ecosystem operates independently of sunlight, powered by a warm stream loaded with dissolved hydrogen sulfide that gives the cave its distinctive rotten-egg odor. The water maintains a constant temperature of about 26 °C (79 °F) and supports sulfur-oxidizing bacteria that form thick white biofilms. These microbes are eaten by midge larvae and isopods, which in turn become prey for the spiders, creating a self-contained food web.
Genetic analysis revealed that the cave spiders have evolved in isolation, possessing unique DNA not found in surface populations. The researchers also discovered that the T. domestica spiders laid significantly fewer eggs than their above-ground counterparts, likely due to the high-energy demands of the dark, low-oxygen environment and the absence of predators reducing pressure to maintain large populations.
"Our findings unveil a unique case of facultative coloniality in this cosmopolitan spider, likely driven by resource abundance in a chemoautotrophic cave," the researchers noted in their study. The discovery provides new insights into how species adapt to extreme environments and how resource availability can fundamentally alter animal behavior and social structures.
This finding follows other recent discoveries about life adapting to darkness, including microbes evolving different survival strategies in cheese caves. While Sulfur Cave might seem inhospitable to humans, it demonstrates the remarkable flexibility of life when faced with challenging conditions, showing how common surface species can completely transform their behavior and biology to thrive in extreme habitats.