"Hey Dad", the boy said. "Why don't spiders stick to their own webs?"
"Well", I said, "You see, spiders use 2 different kinds of silk when they make their webs, one is sticky, one isn't. The spider knows which isn't sticky, so that's the one it steps on."
"Wow, Dad, you sure do know a lot." said the boy.
"I sure, do." I replied, "I sure do."