While most people think of arachnids collectively as being just spiders, and tarantulas as being just spiders, it's a bit more complicated than you'd think! In fact, tarantulas aren't considered "true spiders" and the entire arachnid order includes scorpions, ticks and mites, and harvestmen. Tarantulas belong to an infraorder of spiders known as Mygalmorphic (Mygalomorphae) spiders and are known for their thick/heavy-bodies, thick legs, and downward pointing fangs as compared to true spiders which have pincer-like fangs and small bodies and legs. Within the Mygalomorph infraorder, tarantulas have their very own family of species, Theraphosidae (referred to as tarantulas from here on out). Because of this, tarantulas are considered close cousins to other spiders of the Mygalomorph infraorder and similar to trap-door, funnel-web, and mouse spiders while more-so distant relatives to true spiders like wolf spiders and common house spiders.
While being considered less evolved than their true spider counterparts, Mygalomorphs are considerably larger and stronger in comparison and females can have impressive lifespans of 20+ years! Due to their size, they also have an extra set of book lungs and two claws per foot to help them climb with their heavier weight.
The main difference, however, is the orientation of their fangs. Mygalomorphic spiders have massive downward-pointing chelicerae which their fangs are connected to and which hold their venom glands. Because they are downward-pointing, they can only bite from upwards to downwards in a parallel direction whereas true spiders have pincer-like fangs that can rotate to give them better angles and leverage to bite. There are also some additional minor differences in how their bodies are structured and proportioned.
Below are two tables that give a better visual representation of how the Arachnid class is organized and where tarantulas sit within.
One of the main distinctions that make tarantulas unique from their Mygalomorph cousins is that they are considerably hairier! Tarantulas have the appearance of being quite fluffy whereas most spiders tend to have little, if any, hair and are more often bald or shiny in appearance as compared below. These sensitive hairs allow them to detect subtle vibrations of prey or predators and can even be used for self-defense! Tarantulas also do not have life-threatening venom compared to some spiders like the Brazilian Wandering Spider or the Sydney Funnel-web which would be a bad time if they managed to bite you. Their venom is often compared to be similar to a bee sting, but it should be noted that despite most tarantula venom potency being similar to a bee sting, some tarantulas do possess extremely painful venom and bites can be medically significant or life-threatening if allergies to insect bites exist.Victorian Funnel-web SpiderCurlyhair tarantula
Another distinction is that they do not use their webs as a main strategy for hunting or creating traps. Unlike trapdoor spiders who create trapdoors with silk to ambush prey or orb-weavers who create intricate webs suspended in the air, tarantulas are known for chasing down their prey in the open or patiently waiting until just the right moment to pounce. However, tarantulas do still use strands of web as a sort of trip wire to detect movement from prey or predators.
Types of Tarantulas
Tarantulas themselves also have several main distinctions within their own family which adds to the uniqueness of their behavior and characteristics! Old World and New World tarantulas are two main types and are divided based on geography while terrestrial and arboreal is the difference between tree-dwelling and ground-dwelling tarantulas. Both Old World and New World tarantula species will lie in one or the other category, but some tarantulas exhibit characteristics of both and some even change between terrestrial and arboreal as they mature from a spiderling to an adult.
Old World
As the name suggests, Old World tarantulas are found in continents of the Eastern hemisphere such as Africa, Asia, and Europe. Unlike their New World counterparts, Old World tarantulas do not possess urticating hairs which can be “flicked” from the tarantula’s abdomen - urticating hairs have tiny barbs on the end of them which causes them to stick to would be predators to cause intense itching and irritation as a means of deterrence.
Because of this lack of urticating hairs, Old World tarantulas are known to be much more defensive than New World tarantulas to make up for this lack of defense and generally have much more potent venom. Where a New World tarantula has urticating hairs as a defense mechanism, Old World tarantulas are only able to run, hide, or bite, so be sure to give them some room if they feel threatened.
New World
New World tarantulas, on the other hand, come from the Western hemisphere, North America and South America. These tarantulas do possess urticating hairs which they may flick towards you if they feel threatened, but their venom is typically less painful than Old World tarantulas and they are generally more docile in nature. New World tarantulas make up some of the most popular pets among tarantula hobbyists and are the most agreeable to being handled/held by owners due to the less significant bite and docile behavior.
Sometimes people even “walk” their tarantulas by holding them in their hand, placing their other hand in front of them, and repeating the process until the tarantula has moved from one hand to the other.
It should be noted that handling tarantulas is a very divisive topic among hobbyists as it could cause stress or harm to the tarantula if they become startled and bolt or fall.
Terrestrial
Most tarantulas are terrestrial, ground-dwelling, and tend to be a bit more stout than their arboreal counterparts. Terrestrial tarantulas are at home on the ground and often construct burrows partially or fully underground by using their silk to hold dirt, moss, leaves, or anything they can find, together into a comfy home. Some terrestrial tarantulas may use very little web to construct their burrow, but others, like the Greenbottle Blue tarantula are notorious webbers and will cover most if not all of their home in web and tunnels.
Arboreal
Arboreal tarantulas take a bit of a different approach to their homes and dwellings. Arboreal tarantulas typically prefer to be higher up and usually prefer making their home in places like trees or other vertical structures. They take a minimalist approach to their dwellings and typically do not construct burrows or nests. They will usually be out in the open – relying on their camouflage to blend in with their surroundings. Because they are more avid climbers, arboreal tarantulas are generally lengthier and thinner compared to terrestrial tarantulas but that does not mean they are always smaller overall. Some arboreal tarantulas, like the Singapore Blue, can reach an impressive leg span of nine or more inches.
Behavior
Most tarantulas share some common characteristics when it comes to their behavior. Tarantulas are typically nocturnal creatures and tend to be photosensitive (sensitive to light) and will often be hidden away in their burrow or hiding spot during the day. But when the sun sets, most tarantulas leave their burrows and hiding spots to hunt and explore nearby or sit at the edge of their burrow waiting for prey. Some tarantulas, like the Singapore Blue and Vietnamese Tiger Rump, are extremely reclusive and are usually only found in the open at night.
Vietnamese Tiger Rump sitting in its burrowVietnamese Tiger Rump exploring
On the other hand, some tarantulas, like the Greenbottle Blue or Guatemalan Tiger Rump, are not shy about being in the open and can be seen at various times throughout the day and night waiting for prey or resting on their favorite spot.
They are also extremely patient and deliberate in their movement. Tarantulas can sit in one place without moving for hours. When they do move, it’s often very slowly and carefully to conserve energy. Because of this, tarantulas can go weeks or even months without food! Even when prey is nearby, they will slowly stalk it until just the right moment to pounce, which can happen so fast if you blink you might miss it!
Appearance
One of the most beautiful and unique characteristics of tarantulas is the myriad of shapes and colors they come in. Even cooler, is that some tarantulas will change colors as they mature from spiderlings to adults and even vary in color from male to female! The Greenbottle Blue tarantula will begin as gold, black, and orange and as it matures it becomes a distinct green, blue, and orange color. On the other hand, the Ghost Baboon tarantula will begin as a black/dark grey spiderling and as it matures it will turn bone white in color.
Greenbottle Blue spiderlingGreenbottle Blue adult
Some tarantulas also have metallic-like colorations on different parts of their body like the Singapore Blue which has metallic green/blue colorations on the underside of its footpads. Some tarantulas even come in pink, purple, red, and yellow!
Singapore Blue feetHorned Baboon tarantulaBack to Top
