National Geographic Channel
As Spider-Man 2 swings into movie theaters, a new species of spider has been discovered, and it has a knack for creating well-ordered webs.
Until now there were just four known instances of spiders evolving the ability to measure and create symmetrical webs: The fifth was discovered in Peru last month, prompting questions as to how and why some spiders develop the skill.
"It's interesting because it doesn't make any sense. There doesn't seem to be any advantage to having a symmetrical web, yet it evolved independently among spiders more than once," said Jonathan Coddington, a senior scientist at the Smithsonian Institution in Washington, D.C. Coddington has studied spiders for over twenty years.
"It's not possible that this is a just random drift in evolution and these spiders are stumbling into the ability to measure things. It must have evolved for a reason, but we don't know what that reason is yet."
The Webs They Weave
Of the more than 37,000 species of spiders, all of them can make silk, but only about half use the silk to spin webs. The rest use silk to wrap prey or eggs; weave small, temporary shelters; or create a safety line if they are jumping, Spider-Man style.
The silk emerges from short, muscular projections called spinnerets, usually at the posterior of the abdomen. "The silk is in liquid form in their abdomen which emerges as a solid thread: Researchers are still working out how that happens," explained Linda Rayor, an assistant professor in the department of entomology at Cornell University in Ithaca, New York.
"The silk is stronger than steel for its width and of course far more flexible. It can stretch to 200 times its length."
Each species of spider has a style of weaving that is both innate and easily recognizable to an expert. "Show me any web on Earth and I can tell you what species of spider built it," Coddington said. "Just like an art expert can recognize a Michelangelo or a van Gogh as soon as they see one."
However, just as each painting is unique, each web is customized by a spider to fit the specific space where they're building. "Spiders will alter the design of the web based on wind conditions or the surrounding vegetation," explained Robert B. Suter, professor of biology at Vassar College in Poughkeepsie, New York.
Among the best known symmetrical webs are those of orb spiders. "There are around 5,000 species that spin orb webs," Coddington said.
SOURCES AND RELATED WEB SITES