M. Joel Bagby, age 8, of Santa Maria, California, for his question:

Why doesn't a spider get caught in her own web?

When a fly buzzes into a spider web, she gets all tangled up in the sticky threads and cannot escape. The more she struggles, the tighter the tangles become. Meantime, the spider watches from her secret corner. When the fly stops struggling, the spider strides forth on her eight skinny legs. You would expect her to get tangled in the web also, but she does not.

This is because the spider added some tricks to her web and she knows just where they are. When she spun the threads around and around the web, she added tacky goo to make them sticky. But she added no sticky stuff to the stronger threads that go across her web. The fly gets caught in the sticky threads. But when the spider strides forth, she carefully places each of her eight feet on the non sticky threads. And, since she designed and spun the web herself, she knows just which of the silken threads are safe to walk upon.