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12 Unique Characteristics of Spiders

While people sometimes refer to spiders as insects, they’re actually arachnids, a class of animal that also includes scorpions and ticks. Spiders can be found all over the world, and there are more than 50,000 known species.

If you look at these 50,000 species, you’ll spot all kinds of differences. Spiders can greatly in size, color, and behavior. Below, you’ll find more about the characteristics of spiders and learn more about the traits that make them stand out from other arachnids and animals in general.

What Is a Characteristic In Animals?

Characteristics are the biological traits that are used to identify and categorize animals. Every animal species has specific features that help to separate it from other creatures.

While characteristics are sometimes referred to as “features” or “traits,” these terms can be used to refer to all of an animal’s attributes. A characteristic is a trait that can be used to characterize an animal. This means that all of an animal’s characteristics can be observed in some way.

12 Characteristics of Spiders

1. Eight Legs

Huntsman spider
Huntsman spider | Image by laughoverlouder from Pixabay

One of the most well-known characteristics of a spiders is its eight legs. Spider legs are long and thin, and their legs are divided up into seven distinct parts.

A spider uses all of its eight legs to walk and navigate its environment. Its legs are divided into pairs, with four legs on each side of its body.

2. Spinnerets

Not all spiders weave webs, but every spider has the ability to make silk. They’re able to do this thanks to a silk-spinning organ known as a spinneret. Most spiders have six spinnerets, but the total number can vary based on the spider’s species.

Usually, you can find spinnerets on the underside of a spider. Spiders can use the silk from their spinnerets to make webs, egg sacs, and protective cocoons. In addition, spiders can use silk to capture prey, explore their environment, and may even use it as a source of food!

3. Segmented Bodies

Joro spider
Joro spider | image by Daniel Ramirez via Flickr | CC BY 2.0

Insects and spiders both have segmented bodies, but a spider’s body is split up into two segments rather than three. These segments are called tagmata. Both of these segments have a similar function.

The two segments of a spider’s body are connected by something called a pedicel. Pedicels are thin and extremely flexible. Thanks to this, spiders are able to move their abdomens in different directions.

4. Pedipalps

Unlike insects, spiders don’t have antennae. However, they do have a feature similar to antennae: pedipalps. These appendages look like small legs, but are actually part of a spider’s mouth!

Spiders are able to use pedipalps to get a better sense of the environment around them. Some spider species also use pedipalps to shape webs or to feed on prey.

5. Simple Eyes

Jumping spider
Jumping spider

The number of eyes that a spider has can vary greatly from species to species. Most spiders have eight eyes, but other species may have six, four, or even fewer eyes. What’s true of all spiders is that they have simple eyes.

What are simple eyes? These eyes are sometimes called “pigment pits.” They only have one lens, and they don’t have an elaborate retina, which means that most spiders have limited vision.

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6. Exoskeletons

Humans and many animals have internal support frames, but a spider’s body is supported by a hard protective layer called an exoskeleton. A spider’s exoskeleton is divided into segments, giving it protection without interfering with its movement.

These exoskeletons are made from protein and layers of a natural polymer called chitin. A spider’s exoskeleton can’t expand, and because of that, spiders have to shed their exoskeletons and form new ones as they grow. This process is known as molting.

7. Open Circulatory Systems

Australian redback spider on wood
Australian redback spider on wood | image by John Tann via Flickr | CC BY 2.0

Instead of veins, spiders have open circulatory systems. Their bodies are filled with haemolymph, a fluid that’s similar to blood. It’s made up of organic compounds, inorganic salts, and water.

A spider’s internal organs are located in cavities called sinuses. Their arteries are able to pump haemolymph to these cavities, providing its organs with oxygen and nutrients.

8. Internal and External Digestive Systems

While spiders are only able to eat liquid foods, they don’t just suck the juices from their prey. Instead, they have two digestive systems. A spider’s digestive system is expansive, with some parts extending as far as its legs!

When spiders eat solid foods, they use their external digestive system to digest the prey while it’s still outside its body. Once this process is finished, the digested enzymes are transferred to the spider’s internal digestive system.

9. Flexor Muscles

Spiders move in an unusual way. Most animals have extensor muscles, which are used to move limbs outward. However, spiders only have inward-flexing flexor muscles.

This means that spiders have to use hydraulic pressure in order to extend their limbs outward. When spiders need to use their legs, they increase pressure in their cephalothorax, which is the larger segment of their body. This causes fluid to flow to the spider’s legs, which causes the legs to move outward.

10. Sensory Leg Hairs

Spider on cobweb
Spider on cobweb | Image by Melani Marfeld from Pixabay

If you look closely at a spider’s legs, you’ll spot tiny hairs known as trichobothria. These hairs are able to detect air movement and can even help spiders hear what’s happening around them.

Every spider has at least 20 of these leg hairs, but some have more than 100! Each hair is directly connected to some of the spider’s nerve cells. They use these hairs to locate prey and learn more about the environment around them.

11. Sexual Dimorphism

Spiders show sexual dimorphism, which means it’s easy to distinguish between males and females. One of the easiest and most consistent ways to tell the difference between a male and female spider is to look at the shape of its pedipalps. However, there are many other differences that can be spotted across various spider species.

Female spiders are usually much larger than male spiders. It’s also common for male and female spiders of the same species to have different colors or markings. While many animals show sexual dimorphism, the differences in male and female spiders are more dramatic than what you might see in other animals.

12. Chelicerae

Woodloose hunter fangs
Woodloose hunter fangs | Image by Ian Lindsay from Pixabay

Chelicerae are mouthparts that resemble jaws or fangs. Nearly all spiders have venom glands that are connected to their chelicerae. Spiders are able to use these mouthparts to inject venom into their prey.

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People often assume that venomous spiders are dangerous, but many spiders with venom glands aren’t harmful to humans. In fact, some spider have mouthparts that are too small to bite humans. With that said, the tips of a spider’s chelicerae can be extremely sharp.