100 Million Year Old Ancient Spider Attack Trapped in Amber

One of the oldest evidence of the social behaviour in spiders has been trapped in a fossil that is110 million years old. The fossil of an ancient spider attack was discovered by the researchers from Orgeon State University. This is the only fossil that clearly depicts a spider attack on prey trapped in its web.

This astonishingly rare fossil was fixed in a piece of amber where it was preserved. It also contains the body of a male spider in the same web. The social behavior of the spider that is being depicted in this fossil continues to exist in certain specie but is very rare. Most spiders have solitary, often cannibalistic lives, and males never withdraw from attacking immature species in the same web.

"This juvenile spider was going to make a meal out of a tiny parasitic wasp, but never quite got to it," said George Poinar, Jr., a professor emeritus of zoology at Oregon State University and world expert on insects trapped in amber.

"This was a male wasp that suddenly found itself trapped in a spider web," Poinar said. "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."

According to the researchers, the oldest fossil evidence ever found of a spider web is only about 130 million years old. But such an example of an actual attack between a spider and its prey caught in the web has never before been documented as a fossil.

Both the spider and the wasp belong to extinct genera . There were nearly 15 unbroken strands of spider silk in the amber piece. And on some of these the wasp was ensnared.

The researchers predict that the spider, which may have been waiting patiently for hours to capture some prey, was held back in resin just a split second before its attack.

This type of wasp, Poinar said, belongs to a group that is known today to parasitize spider and insect eggs. In that context, the attack by the spider, an orb-weaver, might be considered payback.

The detail of this finding is being published in the journal Historical Biology.