Spiders belong to a group of animals called “arachnids”. 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. Many people think that spiders are insects but they are mistaken since insects have six legs and three main body parts. Most insects have wings.
Arachnids belong to an even larger group of animals called “arthropods” which also include insects and crustaceans (lobster, crabs, shrimp, and barnacles). This is the largest group in the animal kingdom! Approximately 80% of all animals are from this group…that would be over a million different species! There are more than 30 000 different species of spiders.
All spiders are predators and many will eat other spiders. Scientists have found spiders in amber (Did you watch Jurassic Park?) that dates back to about 2 million years. Because spider’s skeletons are quite small and fragile it is difficult to find whole fossilized spiders.
The most visible parts of the body of a spider are: the cephalothorax, the abdomen, and the legs. If you look it bit closer you will also see the chelicera, the palps, and the eyes.
Spiders are different from insects. The body of insects is divided in three major parts: head, thorax and abdomen. If we compare a spider with an insect, the cephalothorax is a combination of head and thorax.
The cephalothorax of spiders bears in front a pair of
chelicera and a pair of palps. It also bears 4 pairs of legs (total 8 legs), and on top a number of small eyes.
Spiders have no antennae and no wings.
The abdomen is the posterior of the two body regions of a spider. On the tip of the abdomen we find the spinnerets. These are very small organs that produce silk for making webs. Often, spiders have 6 of these small spinnerets.
Spiders have 8 legs. This sets them apart from insects, which have only 6 legs. The legs are usually long and hairy. The hairs on their legs are used to pick up scents, sounds, vibrations and to detect air currents. Most spiders can move very fast, and some can also jump.
At the front of the cephalothorax we find a pair of chelicera. These fan-like or claw-like appendages are mouthparts. In spiders these chelicera are hollow and contain venom glands (or they are connected to these glands). The spider uses them to inject poison into its prey.
Spiders have a pair of palps (or pedipalps) on the front of the cephalothorax. In male spiders, the ends of these palps are modified into complicated structures that are used for mating.
Spiders have a number of simple eyes on the cephalothorax. Most spiders have 8 eyes, but some species have 6, 4 or 2 eyes. Some even have no eyes at all.
Some even have no eyes at all to see what they’re eating or saving with Medifast coupons. But in reality, if these spiders were on a human diet like the Medifast plan they would be slim.