Arachnid super-web reveals the surprising ‘constant party’ life of cohabiting spiders

What is thought to be the world’s largest known spider web, containing tens of thousands of people spidersIt was discovered in a cave on the Albania-Greece border.

After researchers published their findings of two different spider species living together peacefully in a giant colony nestled in a pitch-black, sulfur-rich cave, evolutionary biologist Lena Grinsted likened the “extremely rare” phenomenon to humans living in a block of flats.

Dr D., a senior lecturer at the University of Portsmouth in the UK. “I was very excited when I saw this study because … group living is really rare in spiders,” Grinsted told the Associated Press. “I find the fact that there is this huge colony of spiders living in a place that no one has noticed before is extremely exciting.”

The results of the study, published last month in the journal Subterranean Biology, went viral online due to the striking images of the giant 1,140-square-metre spider web, a carpet-thick area stretching along a narrow passage wall inside the Sulfur Cave, stretching from its entrance in Greece to Albania.

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

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

Two different species of spiders (about 69,000 Tegenaria Domestica, or common house spiders, and 42,000 Prinerigone vagians) lived and thrived side by side. This never-before-observed behavior stunned scientists; because the larger house spider often preyed on its smaller neighbor.

Dr. D., who was not part of the cave study but has researched spiders extensively. “A lot of times if you have spiders in your immediate environment, they’ll fight and end up eating each other,” Grinsted said. “Sometimes we can see that when there is an abundance of food they become a little less aggressive.”

Abundant food source

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

According to the study, part of the answer may lie in the combination of the estimated 2.4 million sandflies buzzing around the spider colony; it is an “unusually dense flock” that provides a constant food source in an environment where predators are normally scarce. Scientists also suggest that this friendly living arrangement may be because darkness negatively affects spiders’ vision.

However, Dr. Grinsted suggests that large spiders may have evolved or become accustomed to responding to vibrating cues when small flies land on their silky webs and would not otherwise attack.

“Spiders in general are not very good at seeing objects… and that includes these two species,” he said. He added that the two genres “can cooperate to some extent in web creation”; “But I think it is unlikely that they would cooperate in anything else, such as capturing prey, caring for cubs, or caring for each other’s young.”

Dr. Grinsted draws parallels between spiders living together and the tendency for humans to live together in apartment blocks.

“You are very happy to share the stairs and the elevator,” he said. “But if someone comes into your living room and you haven’t invited them, you become aggressive towards them.”

He added that although many spiders are “typically solitary and very aggressive” towards other creatures, it is “relatively common” for the two species to live together once spiders have developed the ability to live in groups.

“But still, these two species have never been seen living together or living in groups, which makes it particularly exciting,” he said.

‘The web is dense, like a blanket’

One of the co-authors of the research paper, biologist and zoologist Dr. Blerina Vrenozi told the AP that this year’s expeditions helped understand “how this mystery exists there.”

“DNA is interesting because they revealed that species that live in caves are different from species that live outside caves,” he said. “So it’s the same species but different DNA.”

The cave colony’s massive network 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, leading to the recently published scientific paper.

“The web is dense; it’s more like a blanket, and when there’s danger the female crawls back and hides, and no higher-level creature can get her out,” Audy said. “Cave spiders lay one-third as many eggs as open-air spiders. Because they will certainly raise their young there… so they may lay fewer eggs.”

Audy added that the cave, which is also home to large bat colonies, also thrives on the abundance of sandflies in the moist and dark area. “They have parties there all the time, both spiders and bats,” he said.

Seemingly ideal environment

The study noted that the methodology used may “slightly overestimate” the total number of spider populations in the colony, as some funnel webs may have been abandoned or empty. But other experts agree that the team’s exciting new research may offer broader evolutionary clues and deserves deeper study.

Professor of evolutionary biology and genetics at the School of Life Sciences at the University of Nottingham, UK. Sara Goodacre says such research projects help pave the way for further studies that “could be fundamental to our understanding of what forces (spiderlike or not) shape the world around us.”

“Natural selection will favor ‘best’ strategies… ‘winning strategy,’ whatever that is,” he said. “My guess is that the benefits of being a part of this community far outweigh the costs.”

If the dynamics in a seemingly ideal environment with abundant food and relative security change, “then ‘freeloading’ will occur and everything will collapse,” he added.

We hope that the politics of coexistence will not be more challenging above ground. Audy said Albania has already asked which side the new famous spiders are on.

“From a conservation standpoint, we did something interesting there and drew a boundary,” he said. “I just looked; the spider web is on the Greek side.”

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Stanislav Hodina in Prague; Florent Bajrami in Pristina, Kosovo contributed to this report.