Spiders belong to the Arachnid family. Scorpions, mites, and ticks are also part of the arachnid family. Arachnids are creatures with two body segments, eight legs, no wings or antennae and are not able to chew. There are more than 30,000 known species of spiders. Scientists have found spiders in amber that dates back to about 2 million years. Because spider skeletons are quite small and fragile it is difficult to find whole fossilized spiders. The word spider is from an Old English verb spinnan, meaning "to spin."
Spiders are invertebrates that do not have a backbone. Spiders have an exoskeleton, meaning that their skeleton is on the outside. They are not insects. Most spiders have either six or eight eyes. Most spiders are very nearsighted. To make up for this, they use the hair on their body to feel their way around and to sense when other animals are near.
The existence of spiders is vital to the earth. Spiders eat many types of harmful insects, helping to keep gardens free of pests. Not only do they help pollinate plants, they also help recycle dead animals and plants back into the earth. Spiders are also a food source for many small mammals, birds and fish.
Spiders cannot chew or swallow, so they must digest their food outside their bodies and then drink the liquid. Spiders will inject venom through their fangs and paralyze their victims. The poison turns the insides of insect to a liquid and the spider sucks it up. The insect will often look normal except that the body is empty. Web-spinning spiders will wrap their prey in a web and then crush it’s body with their teeth. They then pour digestive juice over the body and liquefy it. All spiders are predators and many will eat other spiders. Spiders also have these tiny little things on their legs called ‘pedipalps’ that are next to the mouth fangs. They help to hold prey while the spider bites it. Almost all spiders have venom in them.
Most spider poison will not harm people because it is quite weak. There are a few spiders with poison strong enough to cause pain or even some nerve damage in humans. These spiders include the Black Widow and the Brown Recluse spiders. If a bite from one of these spiders is left untreated, death could result. The feared tarantula isn't poisonous. A tarantula's bite can be painful, but it isn't any more dangerous than a bee sting. A fear of spiders is called arachnophobia. It is one of the most common fears among people.
Spiders have silk spinning glands called spinnerets, at the tip of their abdomen. All spiders spin silk, but not all spiders spin webs. The spider’s body has an oil on it to keep the spider from sticking to it’s own web. Silk is used for climbing, to create webs, to build smooth walls in burrows, build egg sacs, and wrap prey. Many spiders use their silk for something called ‘draglines’. This is a rope-like web that helps the spider climb back home if they fall or let themselves drop. Different spiders produce different types of silk. Silk can be sticky, dry or stretchy. Surprisingly, silk is so strong that some spiders use it for traveling. With one end attached to a surface such as a tree branch, the spider will hang onto the end and let the wind carry it away. This is called ‘ballooning’ and can carry the spider many miles. Spiders will recycle their silk. They eat up what isn’t useful anymore and start over with fresh silk. Spider silk is possibly the strongest material in the world. Scientists believe that if they gathered the same weight of spider web as a piece of steel, the web would be much stronger than the steel.
Male spiders are usually smaller than female spiders. Spiders are serious predators so mating can be dangerous especially for the males. Male spiders have to be careful when meeting the female. Using his claws he will send gentle, even vibrations through the web, unlike the quick, jerky movements of scared insects. This announces his arrival, but he still has to convince the female that she shouldn’t eat him in order for them to mate. Spiders are oviparous, which means their babies come from eggs. Spiders will lay between 2 and 1000 eggs, depending on the species. Almost all female spiders protect their eggs by making a silk ‘bed’ and then covering them with a silk ’blanket’. She then wraps them in more silk to make the egg sac. She hangs the sac someplace safe and guards it until the babies hatch. When the babies hatch they often stay inside the sac to finish developing. Some mothers stay until the spiderlings leave the sac, others will either leave or die before seeing their babies. Many spiders will go off on their own after their eggs hatch, leaving the babies to fend for themselves.
All spider webs are designed to catch food. Since spiders do not have great eyesight, they usually use the vibrations of the web strands to locate their prey. When they do, they rush on over and wrap their victim in silk, turning it around and around until it is covered.
Because they are small, spiders have many enemies. Toads, birds, lizards and monkeys hunt them. Spiders are also used as food by many smaller creatures. Ticks will attach themselves to a spider and eat away at it for a long time while the spider goes about its business. One of the spider’s worst enemies is the Spider-Wasp. The female wasp will paralyze the spider by stinging it. She then digs a hole and puts the spider and an egg into it. When the egg hatches, the baby wasp will eat away at the paralyzed spider. Humans are also enemies of spiders. Besides stepping on them, the pesticides we use to control other insects can kill spiders.
The largest spider in the world is the Giant Bird-eating spider. One that was found had a leg span of 11 inches (28 cm). The smallest spider is the Patu Marplesi. You could fit 10 of them on the end of a pencil.