The Texas Brown Tarantula (Aphonopelma hentzi) is one of the largest and most commonly encountered spiders in the southern United States, particularly across Texas. Like nearly all spider species, it is venomous, possessing fangs and producing venom to subdue its prey. While its size inspires fear, the venom is considered medically insignificant to people. This large, hairy arachnid is generally docile, preferring to retreat rather than confront a perceived threat.
Understanding Texas Tarantula Venom
The distinction between “venomous” and “poisonous” is important. A substance is poisonous if it causes harm when ingested or absorbed, while venom is a toxin injected into the body through a bite or sting. The Texas Brown Tarantula is venomous because it injects its toxic secretions through its fangs, primarily to immobilize its prey, which consists of insects and other small invertebrates.
The venom produced by Aphonopelma hentzi is a mild neurotoxin, meaning it affects the nervous system of its prey. For a human, a bite is often compared to a common bee sting in terms of pain and effect. The fangs are large enough to cause a noticeable puncture wound, which is often the most painful part of the encounter. Localized symptoms typically include mild to moderate pain, redness, and slight swelling at the bite site.
The tarantula typically only bites as a last resort when threatened or cornered, often after displaying a warning posture by raising its front legs. It may deliver a “dry bite,” puncturing the skin but not injecting venom, conserving its resources. Systemic or life-threatening reactions are exceptionally rare and are almost exclusively limited to individuals who have a pre-existing severe allergy to spider venom. Anaphylaxis symptoms include difficulty breathing, swelling of the throat or lips, and a rapid heart rate.
The Defense Mechanism of Urticating Hairs
Beyond the venomous bite, the Texas Brown Tarantula uses a unique and often more irritating defense mechanism: urticating hairs. These are tiny, barbed bristles located on the upper surface of the abdomen. When threatened, the tarantula rubs its hind legs against its abdomen, kicking a cloud of these microscopic hairs toward the attacker. This defense is a common trait among tarantulas native to the Americas, known as New World species.
The physical structure of these hairs, with their minute barbs, allows them to easily embed themselves in the skin or mucous membranes. Contact typically results in intense itching, redness, and a rash, similar to a reaction to fiberglass or nettles. The hairs can be problematic if they enter sensitive areas, particularly the eyes, where they can cause inflammation and require medical removal.
Inhaling the hairs is also a concern, as they can irritate the respiratory tract, leading to persistent coughing or difficulty breathing. The rash and itching caused by these hairs can persist for several weeks as the body works to expel the foreign material. Because this defense is the tarantula’s preferred method, contact with urticating hairs is a far more common human complaint than a bite.
What to Do After Contact or a Bite
If bitten by a Texas tarantula, remain calm, as the effects are usually localized and mild. Wash the bite site thoroughly with soap and water to minimize the risk of secondary bacterial infection. Applying a cool compress or ice can reduce swelling and manage localized pain. Over-the-counter pain relievers and antihistamines can address discomfort or minor localized allergic reactions.
If the irritation comes from the urticating hairs, the primary goal is their removal from the skin. Avoid rubbing or scratching the area, as this can break the hairs and drive the barbs deeper into the skin. A practical method for removal is to gently press a piece of adhesive tape, such as duct tape, onto the affected skin and then peel it away, which can lift many of the embedded hairs. Applying a topical steroid cream or an anti-itch lotion can help manage the resulting rash and intense itching.
Seek professional medical attention immediately if the hairs enter your eyes, are inhaled, or if you experience any signs of a severe systemic allergic reaction. Symptoms requiring immediate care include:
- Widespread rash
- Swelling of the face or throat
- Dizziness
- Difficulty breathing