Scorpions are a natural part of the ecology in Arizona’s low desert, particularly in the southern and central parts of the state like the Phoenix and Tucson metropolitan areas. While these arachnids are generally shy and nocturnal, their proximity to human dwellings often leads to concerns about safety and home invasion. Understanding the specific species present and their behavior is the first step in assessing the true extent of the problem.
Prevalence and Identification of Key Species
Arizona is home to over 40 species of scorpions, but only one is considered a serious medical threat: the Arizona Bark Scorpion (Centruroides sculpturatus). This species is small, typically reaching two to three inches in length, and is characterized by its pale yellow or tan coloration and notably slender pincers. Unlike other scorpions, the Bark Scorpion has a thin tail, or metasoma, which is often held coiled to the side when at rest.
The vast majority of other Arizona scorpions are far less of a concern, possessing venom comparable to a bee or wasp sting. For example, the Giant Hairy Scorpion (Hadrurus arizonensis), the largest species in the United States, has a relatively mild sting despite its intimidating size. Similarly, the Striped Tail Scorpion (Paravaejovis spinigerus) is the most common species found statewide, yet its venom poses little threat beyond localized pain. The smaller, slender Bark Scorpion is the one that warrants the most caution.
Assessing the Medical Risk of Stings
The venom of the Arizona Bark Scorpion is neurotoxic, meaning it affects the nervous system, and it is considered the most medically significant scorpion venom in North America. A sting typically results in immediate, intense pain at the site, often described as a burning or electric sensation. This initial discomfort may be followed by numbness and tingling that can spread throughout the body, including the face and extremities.
While stings are rarely lethal to healthy adults, the neurotoxins can cause more severe symptoms, such as muscle twitching, difficulty breathing, excessive salivation, and erratic eye movements. Small children and pets face a higher risk of serious systemic reactions due to their lower body mass, making prompt medical attention necessary. Upon being stung, the wound should be cleaned with soap and water, and a cool compress applied to reduce pain and swelling.
Contact a poison control center immediately for guidance on managing symptoms. Over-the-counter pain relievers like acetaminophen can be used for pain relief. Antihistamines and non-steroidal anti-inflammatory drugs like ibuprofen are generally discouraged unless advised by a medical professional. For severe envenomation, particularly in children, an antivenom may be administered to neutralize the effects of the toxin.
Common Habitats and Entry Points in Homes
Scorpions are nocturnal and seek out dark, cool, and moist environments to shelter from the Arizona heat. Outdoors, they commonly hide under rocks, landscape timbers, woodpiles, and debris that provides cover. The Bark Scorpion is unique in its ability to climb, often found resting high up in tree bark or on block walls.
When outdoor temperatures rise, scorpions are drawn to the cooler, more stable conditions inside homes, often entering through tiny gaps. They can compress their bodies to squeeze through spaces as small as one-sixteenth of an inch. Common entry points include cracks in the foundation, gaps around utility pipes and conduits, and weep holes in brick or block construction.
Once inside, they often inhabit wall voids, attics, and dark areas like closets, shoes, or piles of laundry. Poorly sealed windows and exterior doors are also frequent access points, especially if the weather stripping or door sweeps are worn or damaged. Homeowners can use a blacklight (UV light) at night to identify scorpions, as their exoskeletons fluoresce a bright greenish-yellow color.
Exclusion and Control Measures
The most effective strategy for managing scorpions involves a combination of physical exclusion and habitat modification. Sealing all potential entry points is the first line of defense against indoor encounters. This includes using a high-quality sealant or caulk to fill cracks and crevices in the foundation and exterior walls.
Installing tight-fitting weather stripping around all doors and windows, and making sure door sweeps create a continuous seal against the threshold, is necessary to block ground access. Weep holes in masonry should be screened or plugged with materials that still allow for ventilation and drainage. Eliminating their outdoor food source by maintaining a low insect population also helps deter scorpions.
Outdoor control involves making the yard less hospitable by removing debris, such as piles of wood, rocks, or excessive leaf litter, which scorpions use for shelter. Firewood should be stored well away from the house and elevated off the ground. For chemical control, specialized pesticides can be applied as a barrier treatment around the perimeter of the home. For persistent or widespread issues, professional pest control services often provide the most comprehensive and lasting solution.