Oldest web-spinning Spider found in Amber

The world's oldest orb web-spinning spider has been discovered well trapped in a fragment of amber 120 million years old.

Only 2mm in length, the creature became preserved for several million years ago, must have lived at the time of the dinosaurs - long before the rise of the warm-blooded mammals, according to the of the amber-trapped spider.

The finding in a museum fossil in Alava, Spain, confirms the orb-web as one of the oldest structures used by spiders to capture prey. However, several spiders use webs to catch prey or to protect their young but it is only the true orb-weavers that spin the spiral-shaped aerial structures for trapping flying insects.

The recent find also dates the spider family Araneidae back to the Lower Cretaceous period. Formerly, the oldest recorded web-spinning spider dated back to the Upper Cretaceous period.
David Penney of Manchester University and Vicente Ortuno of Alcala University in Madrid discovered the spider in a piece of amber dug out at Alava in northern Spain.

The fossil was well preserved because amber is fossilized tree resin, which helps prevent biological degradation. The discovery suggests this group of spiders had already developed by the time that flowering plants and insects were undergoing an explosive phase of co-evolution over 100 million years ago, the scientists depicted in their report published in journal Biology Letters.
It is the most ancient fossil species of orb-weaving spider and its existence reveals that this family of spiders was set to exploit the rapid growth in the diversity of pollinating insects.

Dr Penney, who was able to identify the latest found spider by examining the eye arrangement, tarsal claw structure and reproductive organs, said, “One modification is quite fantastic,” added that “Picture a spiral orb web and running down from it a ladder-type structure which is also made from sticky silk. This has evolved to trap moths, which have scales that rub off. When a moth flies into a normal orb web, it's the scales that stick and the moth tumbles out of it.”

“But with the ladder structure, the moth tumbles down until all the scales come off and eventually it gets caught,” Dr Penney stated.