Scientists Found a Spider That Builds 80-Foot Webs, And Its Silk Is Tougher Than Steel

A spider no larger than a coin has upended what scientists thought they knew about natural materials. Discovered in the wilds of Madagascar, Darwin’s bark spider spins silk tougher than Kevlar, a very strong synthetic fiber, setting a new benchmark for biological strength.

According to a study, published in The Journal of Arachnology, the spider builds enormous orb webs across rivers and streams, suspending them on lines more than 80 feet long. Its silk doesn’t just hold, it absorbs energy more efficiently than any known natural or synthetic material.

Found by zoologist Igni Agnarsson and biologist Matjaž Kuntner in 2008, the species (Caerostris darwini) has become a case study in biological innovation. Madagascar’s isolated ecosystem has produced many unusual creatures, but this arachnid stands out not for how it looks, but for what it builds, and how it builds it.

The Largest Webs Ever Measured In Nature

Darwin’s bark spider constructs webs that can stretch over 30 square feet, suspended in midair over rivers. As reported by The Journal of Arachnology, no other eight-legged predator is known to routinely build in such locations, several meters above water, anchored to trees on opposite shores.

This positioning means the webs must endure wind, tension, and the struggles of prey. Igni Agnarsson and Matjaž Kuntner noted that the spiders likely shoot threads across the water, catching them on branches to form the base of the web. Once anchored, they weave the rest of the structure.

While some other web-spinners build near water, none have been documented creating such extensive webs over open air. The demands of this habitat likely drove the evolution of their extraordinary silk, built to withstand not just force but time.

Silk With Unmatched Energy Absorption

The real shock came when researchers tested the silk. The team found it could absorb massive kinetic energy before breaking, outperforming even Kevlar, the material used in bulletproof vests. The silk was described as “10 times better than Kevlar,” not just in strength, but in toughness.

“This spider is famous because it’s been shown that one of the silk types that it makes, called dragline silk, is the toughest spider silk that’s ever been measured,” said evolutionary biologist Jessica Garb of the University of Massachusetts Lowell and lead author of the study avaliable on Communications Biology.

Elasticity plays a central role. The silk stretches twice as far as that of other orb-weaving spiders before snapping. This allows the web to remain intact as prey struggle, storing and dissipating energy without breaking.

The molecular structure responsible for these remarkable qualities remains unknown, though the two experts suggest that future research may reveal what makes this silk so exceptionally effective.

Extreme Structures, Tiny Builder

Though the spider is barely an inch across, its impact is outsize. Agnarsson and Kuntner observed that the webs regularly caught dozens of insects. The size and effort required to build them is enormous, but the nutritional return appears to be worth it.

Interestingly, while no large prey such as birds or bats were observed in the webs, the researchers did not rule out the possibility. The webs are strong enough, and large enough, to hold small vertebrates. With over 40,000 spider species and some 200,000 types of silk estimated in nature, Darwin’s bark spider may be only one of many with remarkable properties.