While all tarantulas are in the spider family, they aren’t like other spiders. It might sound a little complicated, but the whole thing is actually relatively simple.
Tarantulas are not true spiders. Spiders are split into three suborders, and tarantulas are classed differently from most other spiders on Earth. Tarantulas are more primitive and haven’t changed much over millions of years. This means they also have various physical differences no longer seen in more recently evolved species.
This is a fascinating topic but not one that’s essential you understand before getting a pet tarantula or a pet spider. Tarantula keepers often get asked about the difference between a tarantula and a local house spider. Explaining this will amaze anyone who asks and will improve your understanding of tarantulas. Knowing these incredible differences can also give more appreciation for tarantulas and how they’ve stood the test of time.
What is a True Spider?
The spider order is split into three different suborders. True spiders are part of the Araneomorphae suborder and account for at least 90% of all spider species. Spiders in this suborder have fangs that face each other, which is different to tarantula fangs.
True spiders generally have fangs that face towards each other instead of the ground and have more orientations to grab prey with. These spiders also have fewer book lungs (a respiratory organ) and a short life span. Most female true spiders may only live a few years at most.
Almost all spiders are part of the Araneomorphae group, including Orb Weavers, Jumping Spiders, Huntsman Spiders and even Wolf Spiders. However, trapdoors are not in this group. Some of them fit into the Mygalomorphae group, while others are from the Liphistius genus, the sole survivor from the Mesothelae suborder.
Fun fact: The Latin name for the European Wolf Spider is Lycosa tarantula despite it not being a tarantula species.
What are Mygalomorphae Spiders?
Mygalomorphae spiders are an infraorder because this is a suborder inside another suborder of spiders. Mygalomorphae spiders typically have two pairs of book lungs and downward-pointing fangs. Tarantulas, most Trapdoor Spiders and Funnel Web Spiders are part of this group.
This is a group of more primitive spiders than araneomorphae which means they’re physically closer to their distant ancestors compared to more recent species. Spiders in this group are typically heavy-bodied and have stout legs.
While Tarantulas cannot be found wild in the UK, the Purseweb Spider (Atypus affinis) is a species of mygalomorph that lives in the UK. Some other non-native mygalomorphs have been found living within the country, such as those from the Mouse Spider family.
Are Tarantulas True Spiders?
Tarantulas fall into the mygalomorph infraorder of spiders. True spiders are classed into the anaeomorphae suborder. Like other spiders in their infraorder, tarantulas are considered more primitive than true spiders and less evolved in comparison. This means that tarantulas are not true spiders. They are still spiders; they just aren’t evolved enough to be in the anaemorphae suborder.
True spiders are more evolved than older species such as tarantulas. Unlike true spiders, tarantula fangs are fixed and face the floor, giving them a limited biting range, unlike most modern spider species. In addition to this, Tarantulas also have two sets of book lungs (respiratory organs) and are heavy-bodied.
Tarantulas are not in the most primitive spider group will alive today. This title belongs to the mesothelae, which only has a few surviving members in modern times.
Why is a Tarantula not a True Spider?
Tarantulas don’t fit the requirements to be considered a true spider. There are considerable differences between tarantulas and spider species that are true spiders. One of the most obvious is that tarantulas are much heavier bodied and have downward facing fangs, unlike true spider species.
There are a few other significant differences between tarantulas and true spiders. Unlike more recently evolved spider species, tarantulas look physically closer to their ancient arachnid ancestors and behave differently to newer species.
Differences Between Tarantulas and True Spiders
Here are some examples of tarantula features and behavior that true spiders don’t share:
- Tarantulas are covered in sensitive hairs
- Webs weaved by tarantulas aren’t very sticky; these are used to sense prey and where it’s moving
- Tarantulas are ambush predators who run down prey that step onto their feeding web
- Despite their size, tarantula venom is not really a threat to humans, unlike some true spiders
- Tarantulas prefer to live in warmer climates and cannot be found in colder climates
- Longer natural life span
- Tarantulas are often considered to have better eyesight
The fang difference is considered the most significant difference between tarantulas and true spiders; however, this isn’t always obvious when looking at them. Tarantula fangs both face the floor when resting and extended. True spider fangs are positioned facing each other like a pincer. True spiders have a wide range of biting movements giving them different approach options, but tarantulas are more limited.
Why is a Tarantula not a Mesothelae Spider?
Tarantulas are not classed as mesothelae spiders. While tarantulas are more primitive than true spiders, they are not the most primitive species alive on Earth. Mesothelae spiders have a segmented abdomen, and their spinnerets are found in the middle instead of the abdomen.
Mesothelae only has a single family of spider still alive in modern times. Almost all species from this group are not extinct. Liphistiidae spiders are the sole survivors, and they can only be found in Southeast Asia, China and Japan. The species in these groups are typically Trapdoor Spiders though their behaviour ranges. They can also be heavy bodied sometimes.
Tarantulas chase their prey down instead of using a trapdoor. Their spinnerets are found at the end of their abdomen. Tarantulas are also covered in sensitive hairs, which isn’t typical for mesothelae spiders.
Are any Tarantulas a species of True Spider?
There are no species of tarantula that is classed as a true spider. By definition, tarantulas fall into the mygalomorphae infraorder of spiders. True spiders are classed as araeomorphae, which is a different suborder of spiders. Tarantulas can’t be a species of true spider.
While tarantulas and true spiders are different, there can be some overlap. Some true spiders look and behave very similar to tarantulas. Wolf Spiders are often confused for tarantulas due to their looks and hunting style; however, they are not tarantulas. The European Wolf Spider is named “Lycosa tarantula” in Latin, adding to the confusion.
Another point of confusion is the Calisoga true spider species, commonly known as False Tarantulas. These spiders have almost all the typical appearance of tarantulas, including sensitive hairs and a wide, heavy body. However, their fangs are positioned facing each other like a pincer. This means the Calisoga is classed a true spider species and not a tarantula.
Conclusion
Tarantulas are not a true spider, primarily due to their fang difference. Most true spiders look very different to tarantulas due to the evolutionary leap they made. Tarantulas are physically closer to ancient spider species than true spiders. However, they aren’t part of the oldest living order of spiders. Tarantulas are still in the same overall family, but they are not currently classed within the true spiders suborder.
