Weaving a Web
Martin, who confesses he's "not a huge Spider-Man freak," said the movie's web-spinning wonder's powers aren't the same as those of real spiders. "Spider-Man works in a completely different way," he said.
The most familiar of the world's 37,000 spider species may be the orb weavers, spiders that create the wagon-wheel web designs featured in dewy photographs and eerie haunted houses.
Orb weavers, like the golden silk spider Nephila clavipes, spin webs out of spinnerets, organs with precise muscle control found on the spider's abdomen. With the spinnerets' muscles, spiders can open and close the silk ducts and control the thickness of the silk they spin.
Some spiders have as many as seven types of silk, each used for a different purpose. For a wheel-shaped web, the main components are usually dragline silk, a tough thread that makes up the web's scaffolding, and sticky silk, which forms the net to snare a spider's next meal.
This combination is ideal for catching prey, said Todd Blackledge, an entomologist at the University of California, Riverside. "When a fly hits the web, the sticky silk cushions the impact and traps the fly, but the stiff dragline silk absorbs the force and keeps the web intact," he said.
The female N. clavipes produces dragline silk that may be even better at absorbing impact than steel and Kevlar (a brand of protective fiber used to make bullet- and fire-resistant apparel).
Silk isn't used only for webs. Like Spider-Man, spiders can use their silk to travel from place to place using dragline silk. A spider might also employ another silk type, a glue like silk used to connect separate threads, to gain serious distance. "If a spider needs to jump, it might secure its dragline first with this joint cement," Blackledge said.
Other silks are used for forming egg sacsa trick our hero won't likely needand wrapping up prey.
Some spiders get artistic with their webs. Blackledge has studied several species, including the black-and-yellow garden spider and the banded garden spider, which incorporate designs like spirals and crosses into their webs.
These camouflaging designs, called stabilimenta, may be defenses against predators, Blackledge said. In his work, he found that the number and complexity of the designs depended on how hungry the spiders were.
When spiders weave designs, they may be well camouflaged, he said, "but at the same time, insects are spotting the web and veering away." If the spider wants to grab a meal, they might sacrifice some safety for an easier catch.
And to see some fascinating webs, you can still head to the moviesor at least the DVD player. The webs that make up the opening sequence of the first Spider-Man film, Blackledge said, were spot-on. "They had such a great variety of webs," he said. "Somebody had really done their homework."
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