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CORVALLIS, Ore. — A one-of-a-kind fossil has been discovered of a spider attacking prey caught in its web.
The fossil shows a spider attacking a parasitic wasp caught in it web, with another spider nearby on the same web. Researchers at Oregon State University say the 100 million-year-old attack captured in amber provides the oldest evidence of the social behavior of spiders, which is rare in currently existing species.
"This was a male wasp that suddenly found itself trapped in a spider web," said George Poinar Jr., emeritus professor and author of the findings, which will be published in the journal Historical Biology. "This was the wasp's worst nightmare, and it never ended. The wasp was watching the spider just as it was about to be attacked, when tree resin flowed over and captured both of them."
Spiders fossilized in amber, the oldest of which dates back 130 million years, show spiders mating, producing silk, caring for their young and now, killing prey.
The oldest known web preserved in amber dates back 100 million years.
The largest known fossil of a spider dates back 165 million years. The spider's body is nearly an inch long.
The attack took place in the Hukawng Valley of Myanmar in the Early Cretaceous Period, between 97 and 110 million years ago, according to researchers. That means dinosaurs were likely roaming nearby.
Both the spider and the wasp in the fossil are now extinct, according to Poinar. They are almost perfectly preserved because the tree resin that forms amber is able to flow over insects before later turning into a semi-precious stone.
The earliest known fossil of a spider dates back 130 million years. This is the first known discovery of a fossilized spider attack.