Classic Spider Web: Spiders have been surfing the web since the age of dinosaurs. Photo courtesy Mark RyanDid you know the classic structured web that spiders use to capture their prey has been around since the days of the dinosaurs?

A new fossil discovered in Spain contains the oldest known remains of an orb web – the classic structure created by spiders and made up of concentric circles joined by radiating spokes. The web was found in a piece of amber–fossilized tree sap–dating back to the early Cretaceous period, about 110 million years ago.

The oldest known spiders were scurrying about the planet around 400 million years. And fossils of spiders are common, but fossils of their extruded silk products are very rare. The recent find, locked inside the small piece of amber, contains twenty-six web strands along with remnants of typical spider prey such as a fly, a mite and a beetle.

“The advanced structure of this fossilized web, along with the type of prey that the web caught, indicates that spiders have been fishing insects from the air for a very long time,” said David Grimaldi, curator of invertebrate zoology at the American Museum of Natural History.

Two groups of spiders, Araneoidea and Deinopoidea, produce orb webs. Both types have similar proteins in their silk, but the former entraps prey with droplets of glue on the web strands, while the latter uses a dry Velcro-like substance for the same purpose. Scientists now think the two types arose from a common ancestor and then modified their individual trapping techniques.

What this all means is that spiders and their prey-snaring methods could have driven the evolution of insects and their defenses against such methods. Moths and butterflies are members of the family Lepidoptera, and are covered in scales that allow them to roll out of gooey web traps.

“And it happens that Lepidoptera evolved around the same time that spiders produced these webs,” Grimaldi said.

Story links:
American Museum of Natural History story
New Scientist article
New York Times article

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