Oh, what a sticky web they wove

A look inside a piece of 130-million-year-old amber found in Lebanon has revealed a gossamer treasure: a filament of spider silk laced with sticky droplets that look just like those from modern spiders.

The 4-millimeter-long strand of viscid silk–the glue-covered type that some web-spinning spiders use to capture prey–is more than 90 million years older than any known sample of spider silk.

Despite its age, the strand has hallmarks of modern spider silk, says Samuel Zschokke, a biologist at the University of Basel in Switzerland. For example, most of the filament’s glue droplets range from 7 to 29 micrometers in diameter and are arranged in an alternating sequence of small and large. Zschokke describes the delicate fossil in the Aug. 7 Nature.

Both modern orb-weaver spiders and comb-footed spiders spin this type of silk. If the fossil filament came from an ancestor of one of those varieties, it was probably a comb-footed spider, says Zschokke. Today, those arachnids are the only ones that spin webs bearing viscid silk near tree trunks, where seeping resin would be likely to trap a stray strand of silk.


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