The World's Largest Spiderweb Has 111,000 Residents. They Shouldn't Be Sharing.

Deep inside a pitch-black cave straddling the Albanian-Greek border, researchers found something that shouldn't exist: over 111,000 spiders sharing a single web the size of half a tennis court, built by two species that aren't known to cooperate and, under normal circumstances, would simply eat each other.

The colony was formally documented in a study published Oct. 17 in the journal Subterranean Biology. Plastered along a low-ceilinged passage near the cave entrance, the structure covers 1,140 square feet (106 square meters) — woven from thousands of individual funnel-shaped webs.

The cave itself is doing something unusual too. Sulfur Cave was hollowed out by sulfuric acid formed from the oxidation of hydrogen sulfide in groundwater. A sulfur-rich stream feeds a chemical chain from bacteria to midges to spiders, a system that depends on reactions most living things would find lethal. The spiders aren't thriving in spite of the environment. They're thriving because of it.

Two species share the structure: about 69,000 Tegenaria domestica (the common house spider) and 42,000 Prinerigone vagans. The behavior stunned scientists, as the larger house spider would typically prey on its smaller neighbor. This is the first evidence of colonial behavior in either species and likely represents the largest spiderweb in the world, according to lead author István Urák.

Evolutionary biologist Lena Grinsted called the occurrence "extremely rare," noting that "group living is really rare in spiders." Her read on the cohabitation: think humans in an apartment building, happy to share the stairs and the lift, but aggressive the moment anyone wanders uninvited into the living room.

Two solitary predators decided, in total darkness, inside a cave that runs on acid, to build something together instead.

Read the full story at Euronews, November 7, 2025

Hot Take: The house spider is one of the most common animals on Earth — it lives in literally every human dwelling on the planet — and we just found out it's capable of building a 111,000-spider colonial megacity in a sulfur cave, which means everything we thought we knew about what "common" animals are doing when we're not watching deserves a serious second look.