Tarantulas: Anatomy, Habitat & Bite

Instructor: Jennifer Pettigrew

Jennifer has a master's degree in nursing and been a clinical instructor for BSN students.

Many people are scared of tarantulas. In fact, the fear of spiders is the most common fear world-wide. Read this lesson to learn more about the tarantula, maybe you'll see that they're not so scary after all.

A Not-So Itsy-Bitsy Spider

What do you think of when you think of tarantulas? No doubt an image comes to mind of a large, hairy spider that is black or brown. You might think of the spider monsters in The Lord of the Rings or Harry Potter and the Chamber of Secrets or any number of B-list horror films featuring tarantulas. But the truth is that these spiders come in a range of sizes and colors, rarely bite, and are often kept as pets.


Tarantulas can vary in size from the size of a quarter (1 inch) to the size of an ultimate frisbee (about 11 inches). All tarantulas have an exoskeleton which serves structural purposes (determining shape, holding body parts together) and protective purposes (preventing dehydration, injuries and infections). They also have a small endoskeleton which aids in muscle attachments in the body.

The Texas Tan Tarantula is the largest in the U.S. and can reach up to a 6 inch leg-span

Tarantulas, like all spiders, have two main body parts plus a set of appendages. The two main body parts are called the prosoma, which is often described as a combination of the spider's head and chest, and the opisthosoma, which is often described as the tarantula's abdomen, although it also contains their lungs and heart. Most of the appendages are attached to the prosoma. The mouth of a spider is like a straw, so whatever it eats must first be liquified, which is accomplished by regurgitating digestive juices onto whatever the tarantula is trying to eat. Tarantulas have eight eyes but they do not see well and rely on other senses to catch food.


The appendages attached to the prosoma include all eight of the spider's legs, plus the pedipalps, and chelicerae. The legs of the tarantula have retractable claws that assist the tarantula with climbing and adhering to surfaces. The pedipalps are feelers that assist with moving and eating. They look like an additional pair of (shorter) legs, sometimes making it appear a tarantula has ten legs. Between the pedipalps are the chelicerae which have fangs at the end. The chelicerae are used primarily for manipulating food but are also used in mating rituals and to care for the egg sac after mating.

The only appendages attached to the opisthosoma are the spinnerets, which the tarantulas use to spin silk.


Each tarantula has several different types of bristles. The bristles are what give tarantulas a 'hairy' appearance, but they are not made of the same material as hair.

Bristles Common to All Tarantulas

One type of bristle is the setae, which have a hair- or spine-like appearance. These bristles are sensory organs that allow them to feel vibrations, detect chemicals in the air, and sense the direction of the wind.

The second type of bristles are the scopulae, which are a dense network of bristles at the end of the tarantula's legs which allow it to stick to surfaces. The strength of these bristles could theoretically allow a tarantula to support an object that weighed over 150 times as much as the tarantula itself!

Bristles Belonging to Only Some Species

One interesting type of bristles belonging to only some species is known as the the plumose or stridulating bristles, which the tarantula can rub together to make a hissing sound when threatened.

The Texas Brown Tarantula is one of the most common tarantulas in the U.S. and has urticating bristles.

Some tarantulas have urticating bristles which they can detach at will. 'Urticating' means 'itching' and the tarantulas use their legs to flick the urticating bristles in the direction of an enemy as a form of self-defense. Interestingly, tarantula urticating bristles were once used in itching powder used to play pranks on people.


There are over 900 species of tarantula and they are found in warmer climates. Tarantulas can be found in North and South America, Asia, Africa, Australia and even southern Europe, so they can live in a number of different environments.

A Colorful Antilles Pinktoe Tarantula.

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