Careful Footwork
Posted by Troy Steele on June 6, 2003
Q: Why do spiders have symbols on their backs?
A: "Why" questions are really difficult to answer in biology so I think it would be better to ask, "how do the symbols on the backs of spiders, help them survive? What is their value to spiders?" Since many spiders do have these symbols or patterns on their bodies, I think it safe to assume there is some advantage to the spiders. The problem is, it's really difficult to find out what they might be.
Different kinds of spiders vary a great deal in their body markings and often the males have a different pattern than the females. The Black Widow spider comes to mind with its red, hour-glass design on its abdomen. It's interesting to note too that many of the different kinds that have these markings, have poor eyesight and rely more on a sense of touch to capture their food and find a mate so they probably don't use vision to identify others of their kind.
You've stumped me on this one - I can't find any information that discusses the value of the symbols on spiders. Maybe this is an area of study you could someday follow up as a biologist! Thanks for your question and I'm sorry I can't be of more help.
John Wiessinger ( June 7, 2003)