It is my personal opinion that the spinning in spiders is a lined trait with the pattern mutation. I plan on using 'spinning spiders' as a possible thesis for my grad paper in the next set of years, and I hope to find out more than "it's related to the spider trait". I want to know how and why they exhibit this behavior, if it's a neurological disorder, or some sort of 'inner ear' problem. But I would definately read Adam's blog on this subject. It's very informative.