How Poisonous Are Tarantulas? Debunking Common Myths

Arthropods are one of the most diverse phyla on earth, and tarantulas are one of the most notorious arachnids. They are not only known for their gigantic size but also for their potential venomous bites. However, are tarantulas as dangerous as people think? In this article, we will explore common misconceptions about tarantulas and their toxicity level. Let’s get started!

Myth 1: Tarantula venom is deadly

One of the most popular misconceptions of tarantulas is that their venom is deadly. It’s true that tarantulas have venom, but its toxicity level is not as potent as we think. Tarantulas usually have mild venom, and it’s not harmful to humans. However, the venom’s strength can vary among species, but none of them are lethal to humans.

Tarantula venom composition

Tarantula venom has a mixture of different compounds, including alkaloids, enzymes, and toxins. These compounds can cause different reactions when injected into prey.

  • Alkaloids – Tarantulas have several alkaloids in their venom, such as serotonin and histamine. These compounds can cause muscle contractions and dilation of blood vessels, leading to paralysis in prey.
  • Enzymes – Enzymes in tarantula venom help to break down tissues, which makes it easier for tarantulas to digest their prey.
  • Toxins – Tarantulas have different types of toxins in their venom, such as neurotoxins and cytotoxins. These toxins can affect the nervous system or damage body cells in prey.

Myth 2: All tarantulas are venomous

Another misconception is that all tarantulas are venomous. It’s true that most tarantulas have venom, but not all have toxic venom. Some tarantulas have venom that is so mild that it’s not harmful to humans.

How to identify venomous tarantulas

Tarantulas that have toxic venom usually have specific features that distinguish them from non-toxic tarantulas.

  • Hairs – Venomous tarantulas have urticating hairs on their abdomen that they use as a defense mechanism. These hairs can cause itching, irritation or even rashes when in contact with human skin.
  • Bite – Venomous tarantulas have fangs that are darker, larger and curved compared to non-toxic tarantulas. They also have venom glands located in their cephalothorax, which can produce venom.

It’s important to note that tarantulas usually only bite as a last resort when they feel threatened or attacked. It’s unlikely that they will bite a human unless they are provoked.

Myth 3: Tarantulas are aggressive and attack humans

Another common misconception about tarantulas is that they are aggressive and attack humans. However, this belief is not true. Tarantulas are solitary creatures that prefer to keep to themselves, and they will only attack if they feel threatened or provoked. Tarantulas usually only bite humans when they perceive them as a threat.

Behavior of Tarantulas

Tarantulas have distinctive behaviors that show their non-aggressive nature. Understanding these behaviors can help prevent unnecessary bites.

  • Retreat – Tarantulas usually retreat when they feel threatened rather than attack. If a tarantula feels threatened by sudden movements or loud noises, it may retreat to its burrow or hide under a rock.
  • Defensive posture – Before attacking, tarantulas usually take a defensive posture, which involves raising their front legs and exposing their fangs. This behavior is a warning to avoid further confrontation.

The key to preventing tarantula bites is to avoid provoking them. Tarantulas are not aggressive creatures and only bite humans as a last resort.

Myth 4: Tarantulas are deadly to humans

Another common fallacy is that tarantulas are deadly to humans. However, this belief is far from true. Tarantulas are not dangerous to humans, and their bites are not fatal.

Effect of Tarantula bites on humans

Tarantula bites can cause localized pain, redness, and swelling, but they are not fatal. The severity of a tarantula bite depends on various factors, such as location of bite, age and health of the person bitten, and species of tarantula.

  • Pain – Tarantula bites can cause localized pain, which can range from mild to severe. The pain usually last for a few hours to a day or two.
  • Redness and swelling – Tarantula bites can cause redness and swelling around the bite area. Sometimes, the swelling can spread to the surrounding tissue.
  • Other symptoms – In rare cases, tarantula bites can cause allergic reactions, fever or nausea. It’s important to seek medical attention if you experience these symptoms after being bitten.

Although a tarantula bite can be painful and uncomfortable, it’s not life-threatening. It’s essential to seek medical attention if you experience symptoms that don’t go away or get worse.


Tarantulas are fascinating creatures that have many misconceptions around their potential danger to humans. However, it’s important to understand the truth behind the myths to appreciate these amazing arachnids. Tarantulas have mild venom that is not harmful to humans, and they are not aggressive creatures that attack at will. Tarantula bites can cause local discomfort, but they are not lethal. Next time you encounter a tarantula, remember that they are more scared of you than you are of them.


  • Q: Are tarantulas dangerous?
    • A: Tarantulas are not dangerous to humans. Their bites may cause localized pain and swelling, but they are not fatal.
  • Q: Are all tarantulas venomous?
    • A: Most tarantulas have venom, but not all of them have toxic venom.
  • Q: Can tarantulas attack humans?
    • A: Tarantulas usually only attack humans as a defense mechanism when they feel threatened or provoked.
  • Q: How can you identify venomous tarantulas?
    • A: Venomous tarantulas usually have urticating hairs on their abdomen and larger, darker fangs.
  • Q: What should you do if you get bitten by a tarantula?
    • A: If you get bitten by a tarantula, clean the wound with soap and water and apply a cold compress. Seek medical attention if you experience any severe symptoms that don’t go away or get worse.


  • Davidson, B. (1994). The current status of tarantula spider venom taxonomy, ecology, and medical importance. Journal of Venomous Animals and Toxins, 1(1), 1-15.
  • Isbister, G. K. (2004). Spider bites. The Lancet, 364(9434), 579-579.
  • Nentwig, W. (2013). Spider Ecophysiology. Springer Science & Business Media.

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