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Spiders: Learn about natures insect exterminator
What are spiders?
Spiders are amazing creatures. They are part of a group of organisms called arachnids. In addition to spiders, this group of critters includes scorpions and pill bugs.
Spiders are not insects or bugs.
The spider on the left has two body segments and eight legs. Insects, like the ant on the right, have three segments and six legs.
Spiders have eight legs and eight eyes, but no ears. Instead of hearing, they feel vibrations with tiny hairs on their legs. Their bodies have two parts, the head and the abdomen.
Because they have an external skeleton that doesn’t grow, as a spider gets bigger it sheds its old skin and reveals a new one that has been formed. Sometimes we find these old exoskeletons and mistake them for dead spiders.
Some spiders are hairy, others are smooth. Most of them are voracious predators and eat other spiders, insects and even small animals.
Some people are afraid of spiders. This is called arachnophobia. Studies show that 50% of women are afraid of spiders and 10% of men.
Although spiders have fangs and venom (poison), only a very few are dangerous to humans.
Because spiders eat so many insects, like the one below eating a fly, they are good to have around.
Crab spiders, like this one eating a fly on a sunflower, are often the same color as the flower they hide on. One variety of crab spider can actually change color.
Crab spiders don’t spin webs, but hide and wait for dinner to come to them. Since flowers attract insects, crab spiders like to hide on blossoms.
Activity: Cookie spiders
Here’s a fun activity to help remember that all spiders have eight legs.
You will need enough chocolate sandwich cookies for each person and some thin black licorice.
Cut the licorice into segments about two inches long. Push eight of these licorice legs into the creamy center of the cookie. You can use jelly beans or frosting to make eyes.
After you’ve had some fun with your spiders, eat them. Now you can remember you ate the spiders with eight legs.
NOTE: Sorry the people who made the video didn't know spiders have eight legs. Make sure yours do.
How do spiders walk?
Although spiders have muscles that help them flex their legs, they use hydraulic (liquid) pressure to extend them. Tractors use hydraulics to move their buckets, too. Hydraulic oil is pumped into a hollow tube and the pressure pushes a ram out, extending the bucket. When the pressure is released, the bucket will move back to rest on the ground.
If spiders want to move their legs out, they pump them full of blood. This is why dead spiders, who can’t pump blood to their legs, have curled up legs.
Most people think of webs when they think of spiders. Spiders have developed special glands called spinnerets at the tip of their abdomen that are used to make silk. This silk is flexible and very strong, and is used to make webs.
Spider webs come in all different shapes, sizes and forms. Some are used to catch insects, others are made to provide protection. The diving bell spider builds a web under water and then carries air bubbles down to the web to make an underwater house.
The Bolas spider spins a single strand with a sticky end on it. When a moth flies by, the spider throws it’s “lasso” at the moth to catch it.
On the web shown below, the spider is waiting in the center for an insect to fly into the web. When it feels vibration in the strands of the web it will rush to its prey, bite it to incapacitate it, wrap it in silk, and then eat the body fluids.
This web design is called an orb. Orb weaving spiders can make a web like this in about an hour.
About half the insects that get into an orb web will escape before the spider catches them. The center of the web, where the spider waits, is made of dry silk and isn’t sticky. Some of the strands are also dry. Spiders can move around on their webs because they walk mostly on the dry strands. They also move around on their tip-toes, making minimal contact with the sticky strands. Spiders frequently clean their feet. Some people think that the fluid from the spider’s mouth helps keep their feet from sticking.
Not all spiders weave geometrical webs. Some webs are irregular with silk strands going in every direction. Others weave funnel-shaped webs. Regardless of the shape of the web, most of them are designed to catch prey and signal the spider when something good to eat gets caught in its web.
The diving bell spider builds an underwater web and then carries air bubbles from above the water down to the web. This makes an underwater air chamber where the spiders can live, hunt for food and raise their families.
Activity: Make a web
You will need waxed paper, glue and glitter.
Using the glue, make thin lines on the waxed paper. You can try to duplicate an orb web with its rays and ribbon or you can design your own.
Sprinkle glitter on the glue lines and pour any extra back into its container. When the glue is dry, carefully peel away the wax paper to reveal your web.
Not all spiders spin webs, but all spiders can spin silk. They use their silk to make egg cases to protect their eggs and safety ropes to keep from falling . Baby spiders spin a single strand of silk that rises into the air. The wind catches this silk and lifts the little spider to be carried to a new home by the wind.
Spider babies - A face only a mother could love
Female spiders can lay up to 3,000 eggs in one or more silk egg sacs. Baby are very small but similar in shape to adults. Most spiders live for only one to two years, although some tarantulas can live in captivity for over 20 years. The goliath tarantula is the biggest spider and has legs that can span as much as 12 inches.
Activity: How to lift a spider web
What You'll Need:
Black construction paper
Locate an empty spider web. Lightly cover the web with talcum powder. This will make it easier to see the web. Apply a coat of hair spray to the black construction paper. While the spray is still wet, bring the paper up against the web so that the web sticks to the paper. Apply another light coat of hair spray over the web and allow it to dry.
You will have a long lasting natural masterpiece to display in your home or classroom.
Spiders that hunt
Some spiders don’t use webs to catch prey. They need to hunt instead. Tarantulas, wolf spiders and jumping spiders are examples of hunting spiders. Some of these hunters hide and wait for their victims, others sneak up on them or chase them down.
Jumping spiders sneak to within a couple of body lengths of their prey, raise their front legs and jump. They can jump several times their body length and usually anchor a string of silk to the surface they jump from before leaping. This way, if they fall, they can climb back up the silk.
Jumping spiders and wolf spiders can move quickly. If you get a chance to watch one as it hunts you will notice that their legs move so fast it’s hard to see them moving. It appears that the spider just transports itself across the surface.
These spiders like to hunt in sunny places. This keeps them warmer and allows them to move faster.
Jumping spiders are known for their curiosity. If approached by a hand or other object, instead of running away as most spiders do, they will often turn to face the object. Sometimes they will raise their front legs in a threatening way to get the object to retreat.
The ant mimicking spider is so good at what it does that most humans don’t even notice that it’s really not an ant. These spiders can be identified by their two body segments and eight legs. Even so, their abdomen has a thin waist-like portion that makes it look like there are three parts. They also hold their front legs out in front of them so they look like antennae. By looking really closely you can see the spider’s fangs and four pairs of eyes.
Ant mimicking spiders eat ants and aphids. By looking like an ant they can get close without the ants knowing they are not just another ant.
How do they do it?
Ever wonder how spiders like the zebra spider on the right can walk across things as smooth as glass? Most spiders that hunt rather than relying on webs have dense tufts of fine hairs at the tips of their legs. These tufts are made up of tiny bristles whose ends are split into hundreds of branches. These microscopic bristles cling to surface imperfections, allowing spiders to walk upside down and on seemingly smooth surfaces.
Fun Fact: Urban legend
Have you ever heard it said that the daddy long-legs spider has the most poisonous venom of any creature on earth, but it’s mouth is too small to bite humans? It’s not true, in fact, it’s doubly not true.
The critter commonly called daddy long-legs isn’t even
a spider. The real name for this critter is the harvestman. Although they are arachnids, they are not spiders and therefore don’t have venom glands.
Even so, there are so many people who believe the legend that the harvestman myth has been shown to be false on both “Bill Nye the Science Guy” and “Myth Busters.”
Activity: Nighttime spider eye safari
Hunting for spiders at night with a flashlight is called spider sniffing. Spider sniffing might sound like something that’s made up, but it really works and can be a fun summer night activity.
What You'll Need:
On any warm summer night grab a flashlight and head for an open field. Places with a lot of leaf litter are especially good for finding spiders and other critters. Tall grass will make it harder to spot spiders. The darker the area, the better the eyes will reflect.
Turn on your flashlight and hold it close to your face just below your eye. Shine the light between ten and twenty feet in front of you. Look down the length of the flashlight barrel. Walk slowly through the area.
You’ll see tiny points of different colored light reflections. These jewel-like points of light are the reflection of your flashlight beam as it bounces off the eyes of spiders and other nighttime creatures.
Keep track of how many sets of eyes you see. How many different colors were there? Were you able to follow the eye spots and find the owner?
Your friends may think you're crazy when you tell them you've been spider sniffing. If you invite them to join you on your next spider sniffing safari, they'll be amazed.