What is thought to be the world’s largest-known spider's web, housing tens of thousands of arachnids, has been discovered in a cave on the Albanian-Greek border.

Researchers published their findings of two different spider species peacefully cohabiting in a giant colony nestled in a pitch-black, sulfur-rich cave, in the journal Subterranean Biology last month.

The results of the study spread rapidly online due to the striking images of the giant 1,140-square-foot spider's web, a carpet-thick sprawl stretching along a narrow passage wall inside Sulphur Cave, which extends into Albania from its entrance in Greece.

This arachnophobe’s worst nightmare was quickly labelled the “world’s largest spider web.”

But the most surprising thing about the spider colony — which boasts an estimated 110,000 spiders — had less to do with its size and more to do with what scientists found inside the huge mass of funnel-shaped webs.

Two different spider species — about 69,000 Tegenaria domestica, or common house spider, and 42,000 Prinerigone vagans — were living side by side and thriving.

The behavior, which had never been observed before, stunned scientists as, typically, the larger house spider would prey on its smaller neighbor.

Scientists are keen to understand how and why the two species came to coexist peacefully in a “permanently dark zone” about 50 meters (164 feet) from the entrance of the cave, carved out by the waters of the Sarandaporo River to form the Vromoner Canyon.

Part of the answer, the research suggests, may lie in the combination of the estimated 2.4 million midge flies that buzz around the spider colony — an “unusually dense swarm” that provides a constant food source in an otherwise predator-scarce environment.

The scientists also speculate that the friendly living arrangement could be a result of darkness impairing the spiders’ vision.

However, evolutionary biologist Lena Grinsted, a senior lecturer at the University of Portsmouth in the UK, says it is more likely that the larger spiders evolved or simply grew accustomed to responding to vibratory cues when the small flies land on their silken web — and maybe don’t attack otherwise.

Grinsted draws parallels between the cohabiting spiders and how humans tend to coexist in apartment blocks where they are happy to share stairs and lifts but might get aggressive towards uninvited guests into their home

Dr. Blerina Vrenozi, a biologist and zoologist at the University of Tirana, in Albania, who co-authored the research paper, told the AP that the expeditions this year helped understand “how this mystery existed in there.”

“The DNA is interesting because they revealed that the species which live inside the cave is different from the one which lives outside the cave,” she said. “So it’s the same species, but different DNA.”

The cave colony's giant web was first observed in 2021 by a team of Czech speleologists led by Marek Audy.

A year later, the Czech team expanded to include scientists from multiple universities, which led to the recently published scientific paper.

The study noted that the methodology used might “slightly overestimate” the total population count of spiders in the colony, as some funnel webs may be abandoned or unoccupied.

However, other experts agree that the team’s exciting new research could offer broader evolutionary clues and deserves deeper study.