October 9th, 2012 by James Ayre
A spider moving in to kill a wasp, a 100-million-year-old scene preserved in time by amber. The only fossil ever found of a spider attacking prey caught in its web was recently discovered by researchers, the frozen actions of the combatants date back over a 100 million-years.
This really amazingly rare fossil, shows, in really remarkable detail, “an action that took place in the Hukawng Valley of Myanmar in the Early Cretaceous between 97-110 million years ago, almost certainly with dinosaurs wandering nearby.”
“Aside from showing the first and only fossil evidence of a spider attacking prey in its web, the piece of amber also contains the body of a male spider in the same web. This provides the oldest evidence of social behavior in spiders, which still exists in some species but is fairly rare. Most spiders have solitary, often cannibalistic lives, and males will not hesitate to attack 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.”
Spiders are very ancient invertebrates whose history dates back at least 200 million years, they’re rare fossils though, “the oldest fossil evidence ever found of a spider web is only about 130 million years old. An actual attack such as this between a spider and its prey caught in the web has never before been documented as a fossil, the researchers said.”
“The tree resin that forms amber is renowned for its ability to flow over insects, small plants and other life forms, preserving them in near perfection before it later turns into a semi-precious stone. It often gives scientists a look into the biology of the distant past. This spider, which may have been waiting patiently for hours to capture some prey, was smothered 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 spider species in the amber and the wasp species both belong to extinct genera and have been described in detail in the research paper. Remarkably there are at least 15 completely unbroken strands of spider silk running “through the amber piece, and on some of these the wasp was ensnared.”
The research was just published in the journal Historical Biology.
Source: Oregon State University
Image Credits: Oregon State University; Orb Weaver via Wikimedia Commons
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