A piece of advice: if you suffer from arachnophobia, don’t read this piece, because it talks about the largest spider web in the world (at least as far as we know). It is located right on the border between Greece and Albania, in a cave called Sulfur Cave, it occupies more than 100 square meters and is inhabited by hundreds of thousands of spiders of two different species.
Discovered in 2022 by a group of speleologists from the Czech Speleological Society, it has now been analyzed more carefully by a team from the Sapientia Hungarian University of Transylvania, in Romania, who published their findings in the journal Subterranean Biology.
The sulfur cave. As the name suggests, the Sulfur Cave is a cave that was formed following the corrosive action of sulfuric acid, in turn produced by the oxidation of the hydrogen sulfide present in the underlying aquifer. It is an extreme ecosystem, in which sunlight never reaches: the bacteria that live there feed on the sulfur present in the stream that passes through it, and in turn are eaten by the midges that live in the cave. Technically this is a case of chemoautotrophy, i.e. the production of energy starting from chemical reactions that take place in the inorganic substrate.
A paradise. In this seemingly inhospitable environment, two different species of spiders have found their paradise, feeding on the aforementioned midges. It’s about Tegenaria domesticathe widespread house spider, and of Prinerigone vagansa species of weaver spider.
The two species coexist without problems, weaving their webs: over time, they have built an immense structure, a real “spider city” with a surface area of 106 square meters and which covers the entire wall of the narrow entrance passage to the cave.
The city of spiders. The study of the largest spider web in the world has not only allowed us to identify the two species that inhabit it, but also to carry out a sort of census: according to the authors’ estimates, 69,000 house spiders and 42,000 weaving spiders live in the city of spiders, which, moreover, according to a molecular analysis, are genetically different from their “relatives” who live in the sunlight. It is therefore an ecosystem that has existed for some time, to which spiders have learned to adapt.
Now the authors of the study plan to return to the cave and carry out further analyses: for example, to find out if the behavior of the Sulfur Cave spiders is also different from that of their conspecifics, but also to delve deeper into the cooperative relationship between two species which, usually, do not need to coexist in the same environment.
