Wonder World Of Science : Why Do Spiders Spin Webs? (1987)

I wonder. I wonder What do you wonder, Wonder Cat? I wonder Why do spiders spin webs? Why do spiders spin webs? If you're curious enough, you can find out by watching spiders. Look at that one over there. Wow, that spider is sure busy, isn't it? Yes, it is. It takes only about half an hour for a spider to build a web like this one. Most spiders build their webs at night. Well, it's morning now, so I guess this one is probably hurrying to finish up. Watch how the spider shapes its web. The web is like a silken net. I see. But where do the threads come from? If you look carefully at the spider, maybe you can find out. Well, it looks like the thread is coming right out of the spider's body. You're right. The threads a spider uses to make a web do come out of its body. They come out of special parts called spinnerets. There they are, those tiny brown bumps on the underside of the spider. Those are the spider's spinnerets. A liquid inside the spider's body hardens when it comes out through the spinnerets into the air. It forms the threads of silk that the spider uses to build its web. The spinnerets make different kinds of silk. The threads that most of the spider's web is made of are strong and sticky. After the web is finished, the spider will hide and wait. This spider has woven a hiding place in the center of its web. What's it waiting for? Look there. At that fly on the leaf? Yes. It flew away. And now it's on the spider's web. It's trying to fly away, but it can't. It looks like it's stuck to the web. The spider feels the web move and knows an insect has landed on it. The spider's crawling over to the fly. It's biting the fly. It bit the fly. That's right. The spider bites the fly to kill it. Now see what the spider is doing. Wow. The spider is using its thread to wrap up the fly. The spider is going to eat the fly later. Oh. So flies, and maybe other insects, too, must be food for spiders. That's right. And spiders must spin webs so they can catch insects. Now I know. Yes, now you know what a web does for a spider. A web helps a spider get its food. Insects get caught in the sticky threads of a web. And once an insect is caught, a spider knows what to do. But what you may not know is that a spider is not an insect. Spiders are called arachnids. Arachnids. I'll try to remember that. Good. Of course, there are all sorts of spiders and many kinds of webs. Wow, there sure are. But I'm still wondering. What do you wonder now? Well, I wonder, why don't spiders get stuck in their own webs? Nobody knows for sure, but some scientists think that special oils may cover the tips of the spider's legs and keep them from sticking when they touch the sticky threads of the web. But spiders sometimes use their silk threads for other things besides making webs and wrapping food. They can also use them as safety lines to get away from an enemy. Like this wasp. Watch. It's over the spider's web. The spider will jump off, but spin a thread as it falls. Watch. And then, when the wasp flies away, the spider goes back up the thread. The spider will wait now for another small insect to be caught in its sticky web. Then it will wrap the insects in silk and maybe even line them up as this spider has done. While all spiders make threads of silk, not all spiders make webs. I guess this big one goes looking for food on the ground. Yes, it does. And I guess this one must wait for its food on plant leaves. Are all four of those its eyes? Yes. I wonder how things look when you see with eyes like that. That's the spider's mouth under the eyes. Maybe it sees some food. It does. That caterpillar. Wow. That spider didn't need sticky threads to catch its food. Some spiders use their threads to make egg cases, like the one this spider mother is carrying. Those babies riding on her back just hatched. Here are many more baby spiders. They're called spiderlings. They hatched out of their tiny eggs just a short time ago. Even newborn spiders make silken threads. They leave a trail of them wherever they go. Sometimes all the baby spiders stay together after hatching and build the web that they all live on. But before long, all the baby spiders will be gone from this web. Many will leave the web blown by the wind that catches the silken threads they're attached to. Each baby will find a new place to live and spin webs of its own. Now I know why spiders spin webs and a lot more about spiders, too. Arachnids. See, I remembered.