Kids' Treehouse

Part of the Tree of Life project

Jumping Spider Treehouse

Welcome to the Jumping Spider Treehouse! We have pictures, and questions and answers about jumping spiders.

Pictures & Stories


Teresa Maddison (4 years old, Tucson, Arizona)

If you want to contribute a picture of a jumping spider you've drawn, then attach it to an e-mail message to Wayne, whose address is wmaddisn@u.arizona.edu. If you want to send in a story about jumping spiders send and e-mail to Wayne. Give your name, age, and the city in which you live.

Questions about Jumping Spiders

Here are some questions and answers to tell you some cool facts about jumping spiders. If you want to ask a question, send it to Wayne, whose address is wmaddisn@u.arizona.edu.
  1. Do spiders have bones?
  2. Why don't jumping spiders have big back legs like a grasshopper?
  3. What is the last thing that goes through a spider's mind as it sheds its skin?
  4. Who dances better, boy spiders or girl spiders?
  5. How do you tell male (boy) spiders from female (girl) spiders?
  6. How do a spider's feet smell?
  7. Do spiders have noses?
  8. Can spiders fly?

Answers!

Do spiders have bones?

No! You and I have bones on the inside. Our muscles surround the bone and pull on it, to make our skeletons (and us!) move. Spiders are built the other way around. Their skeletons aren't made of bone, and they are on the outside, like a shell. The muscles pull on the skeleton from the inside. You might want to check out the jumping spider anatomy page concerning muscles.

Why don't jumping spiders have big back legs like a grasshopper?

You might think that jumping spiders would need big back legs packed full of muscles to jump. But they don't. How do they jump so well? The answer is that spiders don't use muscles in the legs to jump. Instead, they use muscles in the body to increase their blood pressure. The back legs begin curled up behind the body. When the blood pressure rises, the blood squirts into the legs and inflates them. This causes the leg to stick out straight suddenly, which pushes the spider forward quickly. And so it jumps! It's a lot like those toy frogs which have a bulb attached; when you squeeze the bulb, a curled piece of rubber underneath the frog inflates, straightens out, and pushes the frog.

What is the last thing that goes through a spider's mind as it sheds its skin?

Its stomach! The reason is, a spider's gut goes right through the middle of its brain, and when it sheds its skin, it has to shed that part of the gut as well, right through the brain. This deserves some explanation!

A spider's gut proceeds from the mouth, right through the brain, and eventually back into the abdomen to the area where intense digestion is done. The reason the gut goes throught the brain has to do with the spider's ancestry. Originally, many hundreds of millions of year's ago, the jumping spider's ancestors were worms that had a ring of nerves circling the front part of the gut, just back of the mouth. Through evolution, as the spider's ancestors evolved a more discrete head-area with eyes, legs, mouthparts and so on, the nervous tissue controlling all of this stuff got concentrated toward the front end, swelling the original nerve ring into a mass of nervous tissue that we call the brain.

That's why the gut goes through the brain. But why does the stomach have to get shed with the skin? The front part of a spider's gut is lined with cuticle, the hard stuff that makes up the exoskeleton (hard skin) of the spider. In fact, the gut is lined with cuticle all the way back to the sucking stomach, which lies just back of the brain. This part gets yanked through the brain when the spider sheds its skin. To learn more, check out the jumping spider anatomy page concerning the gut.

Who dances better, boy spiders or girl spiders?

Boys! Male spiders do fancy dances to females to impress them. Check out some movies of dances.

How do you tell male (boy) spiders from female (girl) spiders?

Male spiders, when adult, have swollen palpi (the feelers in front of the face). In females the palpi look pretty much just like little legs. Female spiders, when adult, have a little dark spot on the underside of the abdomen (the epigynum), between the book lungs.

How do a spider's feet smell?

The answer is not "terrible!" Actually, spiders' feet probably don't have much of a smell, but they can smell other things! Jumping spiders smell and taste through various sensory organs scattered around the body, including on the tips of the feet and palpi. So when you ask, "How do a jumping spider's feet smell?", the correct answer is "quite effectively, thank you!"

Do spiders have noses?

Well, not really. They do breathe, but very differently than we humans do.

To breathe, jumping spiders use a sort of lung that is in some ways like our lung, although of a very different shape. Whereas our lung is filled with air spaces that are shaped sort of like clumps of grapes, a spider's lung is filled with flat air spaces that are arranged like the pages of a book. A spider's lung is called a book lung, and instead of being up near the front end, it is on the underside of the abdomen, just back of the waist. A jumping spider has two of them, and they are visible (usually) as to pale patches that show through the skin. These lungs exchange oxygen from the outside air to the blood, and carbon dioxide from the blood to the outside.

The other breathing apparatus that jumping spiders have is the set of tracheal tubes, which extend from an opening just in front of the spinnerets on the underside of the abdomen. They are branched like a tree, and extend into the head region. The tracheae are like "air arteries", in that they take the air straight to the tissues.

Can spiders fly?

Yes, but not with wings. Spiders, especially small ones, often get around by letting a long silk out of the spinnerets. This long strand gets caught by the wind, take the spider with it, sometimes hundreds of feet into the air and for quite a distance. It's called ballooning.