Kathryn Hall, age 10, of Libertyville, Illinois, for her question:

How. can a spider walk on her web?

Men a fly flies into a spider web, she gets stuck in a sticky net. If she moves a wing it gets stuck, if she moves a leg it gets stuck. The more she struggles, the tighter the tangles enfold her. Meantime, from a quiet corner the spider watches until the fly has to stop struggling because she is all tied up in sticky threads. Then the cunning spider strides toward her victim    and not one of her eight feet get stuck in the web.

A spider's web is a work of art and she weaves it just so. First she sets up a scaffold of extra strong threads. She leaves them smooth and silky. Then she winds a long thread around and around to make the spiralling crossbars. Every so often she stops and squirts a little goo on these threads. Naturally she knows which threads are sticky and which ones are not. When she walks over her web, she carefully places her feet on the non sticky threads. A fly does not know this secret, so she gets tangled in the sticky threads.