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Spider Webs

November 17, 2005

Each species of spider weaves its own signature web. Science Update answers this listener’s question about a web pattern that seems to be missing something.


A spider web’s missing piece. I’m Bob Hirshon and this is Science Update.

Listener Sharon Knowles of Seattle observed:

When spiders build a web, there’s always a pie-shaped piece that is just vacant—and nobody seems to be able to tell me why.

Smithsonian entomologist Jonathan Coddington says not all webs have a gap. But in those that do, the gap is traversed by a thread called a signal line. It runs from the center hub of the web to the spider’s nearby retreat.

It’s basically a way to transmit vibrations rapidly from the hub to the spider and therefore the spider’s going to run down that same signal line to get to the hub and from there to attack the insect wherever it may be.

Leaving that section vacant may help the spider run down the signal line faster.
Call us at 1-800-why-isit with your science question. I’m Bob Hirshon, for AAAS, the science society.