Purpose To demonstrate how spider webs catch flying insects.
Materials 2-inch (5-cm)-wide transparent tape (sticky on one side 20 to 30 cotton balls
Plastic container large enough to hold the cotton balls adult helper
1. With adult assistance, run a strip of tape from the cen ter of the top of a doorway to the floor. Then run two strips of tape diagonally between opposite corners of the doorway. The sticky side of all of the pieces of tape should face you and be on the same side of the door way.
2. Run more strips of tape horizontally and vertically across the doorway. But leave empty spaces between the strips and turn the horizontal strips so that their sticky side faces away from you.
3. Put the cotton balls in the plastic container.
4. Stand about 3 feet (0.9 m) from the sticky side of the vertical and diagonal strips of tape.
5. Throw the cotton balls, one at a time, toward the tape. Count the number of balls that stick to the tape.
Results Most of the cotton balls that hit the tape strips whose sticky side faces you will stick to the tape.
Why? Spiderwebs are constructed by spiders from silk (a fine, soft fiber made by some insects) made in their bod ies. On the hind end of a spider’s body are pointed bumps called spinnerets. Liquid from inside the spider flows out of the spinnerets, and the spider spins the liquid silk into strands and weaves the strands into a web. One kind of silk dries in the air and is not sticky (represented by the tape strips whose nonsticky side faces you), and another kind stays sticky (represented by the tape strips whose sticky side faces you). Flying insects (represented by the tossed cotton balls) that hit the sticky side of the tape usu ally stick. Others fly between the web strands, hit nonsticky strands, or manage to pull away from the sticky strands. Spiders are also able to walk on the nonsticky strands without getting stuck. But they also don’t get stuck on the sticky strands, because they have a liquid on their feet that keeps them from sticking.