The world's oldest known spider web has been discovered on a beach in Sussex, England, trapped inside an ancient chunk of amber.

Scientists found the rare amber fossil in December, and have now confirmed that it contains remnants of spider silk spun roughly 140 million years ago by an ancestor of modern orb-weaving spiders. After slicing the amber into thin sections and examining each piece under a high-powered microscope, the researchers discovered that the ancient silk threads share several features common to modern spider webs, including droplets of sticky glue used to hold the web together and capture prey.

According to paleobiologist Martin Brasier of Oxford University, the gooey droplets suggest that spiders were starting to spin webs that were better adapted for catching flying insects. "Interestingly, a huge radiation took place in flying insects and bark beetles about 140-130 million years ago," Brasier wrote in an email to Wired.com. "So we may be seeing a co-evolution of spiders and insects here."

The new discovery is the first example of an amber fossil from the early Cretaceous period, when dinosaurs like spinosaurs and psittocosaurs roamed the Earth.

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"Silk is a relatively delicate material and it is rarely preserved in the fossil record, except when entombed in amber," Brasier and colleagues wrote about the discovery in the upcoming December issue of the Journal of the Geological Society. The researchers think pieces of organic material, including the spider silk, became embalmed during a severe wildfire, when amber resins seeped out from the charred bark of coniferous trees and were eventually swept away by flooding.

In addition to ancient spider silk, the amber chunk contains well-preserved soil microbes, including the oldest known examples of actinobacteria, a common type of bacteria that plays a major role in soil formation.

*Image 1: A spider and web trapped in amber, Mila Zinkova/Wikipedia Commons. Image 2: Light micrograph of new amber fossil showing a web of tiny silk threads, plus droplets of sticky glue. Courtesy of Martin Brasier.

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