Spider 'Superweb' Shows Unprecedented Species Cooperation
A groundbreaking discovery in a cave on the Albanian-Greek border has revealed what researchers believe to be the world's largest spider web, but the most significant finding is not the structure's impressive size - it is the unprecedented peaceful cohabitation of two spider species that would normally be predator and prey.
The enormous 1,140-square-foot web was discovered in Sulfur Cave, a humid, sulfur-rich environment carved by the Sarandaporo River. The colony houses an estimated 110,000 spiders: approximately 69,000 Tegenaria domestica (common house spiders) and 42,000 Prinerigone vagans, a considerably smaller species.
The research, published last month in the journal Subterranean Biology, has generated significant excitement in the scientific community because this type of interspecies cooperation has never been documented in spiders before.
Dr. Lena Grinsted, a senior lecturer in evolutionary biology at the University of Portsmouth, expressed her enthusiasm about the finding. Group living itself is extremely rare in spiders, which are typically solitary and aggressive creatures. The discovery of two species that have never been found living together or in groups makes this particularly remarkable.
The peaceful arrangement appears to contradict typical spider behavior. Dr. Grinsted explained that when spiders are in close proximity, they usually fight and end up eating each other. However, abundant food supplies can sometimes reduce aggression.
The cave environment provides several factors that may enable this unusual cooperation. Scientists estimate that approximately 2.4 million midge flies inhabit the cave, creating an unusually dense swarm that offers a constant and abundant food source. This predator-scarce environment appears to reduce competition for resources.
The colony is located in a permanently dark zone approximately 50 meters from the cave entrance. While some researchers initially speculated that darkness might impair the spiders' vision, Dr. Grinsted suggests a more nuanced explanation. She believes the larger spiders have likely evolved to respond specifically to vibratory cues when prey lands on their webs, rather than attacking any movement indiscriminately.
Dr. Grinsted drew an analogy to human apartment living to explain the spiders' social structure. Just as people are happy to share communal spaces like stairs and elevators but become defensive when uninvited individuals enter their private living spaces, the spiders appear to tolerate shared web infrastructure while maintaining individual territories.
The web itself is remarkably dense. Czech speleologist Marek Audy, who first observed the web in 2021, described it as more like a blanket than a typical spider web. This density provides excellent protection, allowing female spiders to retreat deep into the structure where no predator can reach them.
Research conducted by Dr. Blerina Vrenozi, a biologist at the University of Tirana in Albania, revealed fascinating genetic differences. DNA analysis showed that the cave-dwelling spiders have different DNA from the same species living outside the cave, suggesting evolutionary adaptation to the unique cave environment.
The cave spiders also exhibit different reproductive strategies, laying approximately one-third fewer eggs than their outdoor counterparts. Audy explained that because offspring survival is more certain in this protected environment, the spiders can afford to invest in fewer eggs.
The cave also supports large bat colonies that share the abundant midge population. Audy colorfully described the situation, saying both the spiders and bats are constantly having a party in the humid, dark space.
Dr. Sara Goodacre, professor of evolutionary biology and genetics at the University of Nottingham, emphasized the broader significance of such research for understanding evolutionary forces. She suggested that natural selection favors the best strategies, and in this case, the benefits of community living clearly outweigh the costs. However, she cautioned that if environmental dynamics were to change, cooperative behaviors could break down as freeloading emerges.