07/24/2026
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The largest scorpion in the United States has venom so mild it is described as harmless to humans. The most dangerous scorpion in the United States carries a neurotoxin that can hospitalize a person and occasionally kill one. The big one eats the dangerous one. The University of Arizona's College of Agriculture and Life Sciences calls the five-inch Arizona giant hairy scorpion a beneficial addition to your home landscape because it consumes Arizona bark scorpions voraciously.
The Arizona bark scorpion is two to three inches long, pale tan, and slender enough to squeeze through a crack the width of a credit card. It is the only scorpion of medical concern in the United States. Its venom attacks the nervous system. A sting produces immediate intense pain followed by numbness, tingling, muscle twitching, and in severe cases difficulty breathing, drooling, and convulsions.
Children and elderly adults are most at risk. Before antivenom became widely available in Arizona, bark scorpion stings occasionally killed people. The species is the most commonly occurring scorpion in the low desert Southwest, and it is the only scorpion in Arizona that climbs. It walks up walls, across ceilings, into shoes, under sleeping bags, and onto the sides of houses after dark. Most scorpion stings reported to Arizona poison control are bark scorpion stings. Most people who have been stung by a scorpion in the United States were stung by this animal.
The Arizona giant hairy scorpion is a different creature entirely. Adults routinely exceed five inches and can reach seven. The body is heavy and dark across the top with pale yellow legs, claws, and tail. Fine sensory hairs cover the body, giving the species its name. It is a burrowing ambush predator that digs deep shelters in sandy desert soil, emerges at night, and waits for prey to walk past. When something does, the giant hairy scorpion does not rely on its stinger. It grabs the prey with its pedipalps, the massive claws at the front of its body, and crushes it. The claws do the killing. The stinger is a backup. Its venom is weak because it does not need strong venom. It has pliers.
The bark scorpion evolved the opposite strategy. Its claws are narrow and weak. It cannot overpower prey or hold struggling insects the way the giant can. Instead, it runs down prey at speeds of up to 12 miles per hour, grabs it with its slender pedipalps, and immediately delivers a sting loaded with fast-acting neurotoxin. The venom does the work the claws cannot. It immobilizes the prey in seconds. This is why the bark scorpion is dangerous to humans and the giant is not. The bark scorpion invested everything in its chemistry. The giant invested everything in its grip.
When the two meet, size wins. The giant hairy scorpion hunts other scorpions as a regular part of its diet, including bark scorpions and even other giant hairy scorpions. It is cannibalistic and territorial. A bark scorpion that wanders into the territory of a giant hairy scorpion at night faces a predator four times its length with claws strong enough to hold it while eating it alive. The bark scorpion's venom, devastating to a human nervous system, does not stop an animal that outweighs it by a factor of ten and grips it from a direction the stinger cannot easily reach.
The giant hairy scorpion is not common enough to control bark scorpion populations across the Sonoran Desert. It is solitary, slow to reproduce, and occupies large territories relative to the bark scorpion's dense suburban colonies. But where it lives, it hunts bark scorpions with a consistency that the University of Arizona considers ecologically significant. The extension service does not say the giant hairy scorpion occasionally encounters bark scorpions. It says it consumes them voraciously.
The biggest scorpion in the country is nearly harmless to people. The smallest common one can put you in a hospital bed. The big one eats the small one, and the small one cannot do anything about it because the weapon that works on a human nervous system does not work on something that kills with its hands.
Source: University of Arizona, College of Agriculture and Life Sciences / Arizona Cooperative Extension / Blue Sky Pest Control / A-Z Animals / Veseris.
