Arizona is home to a diverse population of scorpions, with approximately 30 different species found across the state’s varied landscapes. These arachnids are a natural component of the desert ecosystem, inhabiting areas from mountain slopes to the valley floors. While the presence of scorpions is common in both urban and rural environments, the potential threat they pose varies dramatically between species. Understanding the distinctions between the types of scorpions encountered is the most effective way for residents and visitors to manage safety and avoid unnecessary concern.
The Most Medically Significant Species
The most medically significant species in Arizona is the Arizona Bark Scorpion (Centruroides sculpturatus). It is the only scorpion species in the United States whose venom is considered life-threatening to humans, though fatalities are rare. This small arachnid typically measures between one and one and a half inches in length, making it comparatively small next to other local species.
Identification relies on specific physical characteristics, as its coloring is an unreliable feature, often appearing as a pale yellow or light tan. The Bark Scorpion has slender, delicate pincers and a narrow tail, distinguishing it from the robust bodies of less venomous scorpions. When resting, this species often holds its tail coiled to the side, rather than curled over its back.
A sting from this scorpion injects a potent neurotoxin that can cause symptoms extending beyond immediate pain. Adults often experience intense, sharp pain at the site, followed by numbness and a tingling sensation that may travel up the affected limb. More severe reactions are possible, especially in young children and older adults.
In children, severe symptoms can include uncontrollable muscle activity, difficulty breathing, excessive salivation, and rapid, jittery eye movements. Unlike stings from other scorpions, the Bark Scorpion sting often causes minimal or no swelling or discoloration at the injection site. Immediate medical attention is necessary if these severe neurological symptoms appear, as antivenom is available for treatment.
Common Scorpions That Pose Little Threat
Most scorpions encountered in Arizona cause stings that are painful but not medically serious, often comparable to a bee or wasp sting. The Desert Hairy Scorpion (Hadrurus arizonensis) is the largest species in the United States, growing up to six or seven inches long. Despite its intimidating size, its venom is relatively mild, typically only causing localized pain and minor swelling.
The Desert Hairy Scorpion is easily recognized by its large, powerful pincers and a thicker tail compared to the Bark Scorpion. Its body is usually yellowish with a darker top and is covered in fine, reddish-brown hairs that give it its name. This species is a burrower, preferring loose, sandy soil where it digs deep shelters.
Another frequently seen species is the Stripe-tailed Scorpion (Vaejovis spinigerus), sometimes called the Devil Scorpion. This scorpion is moderately sized, typically around two and a quarter inches long, and is identified by a prominent dark triangular mark on the head region. It has a stout tail with darkly-marked ridges running lengthwise along the underside, distinguishing it from the slender tail of the Bark Scorpion.
The sting from the Stripe-tailed Scorpion is generally localized and painful, but the effects are usually mild and self-limiting. These larger, more robust scorpions use their powerful pincers to capture prey, relying less on their venom for defense against larger threats.
Identifying Activity and Habitats
Scorpions are nocturnal creatures, emerging primarily at night to hunt when temperatures are lower. They are most active during the warmer months, typically from April through October. During the day, they retreat to cool, dark shelters to avoid the intense desert sun and conserve moisture.
Their preferred habitats include hiding under rocks, logs, loose bark, and outdoor debris. The Arizona Bark Scorpion is unique among local species because it is a climber, frequently found on vertical surfaces like block walls, fences, and even ceilings. This species is attracted to the cool, moist environments found in areas like bathrooms, laundry rooms, and near plumbing fixtures.
Other common species, such as the Desert Hairy Scorpion, are burrowers and are often found in loose, sandy soil. Scorpions can enter homes through small cracks and crevices, sometimes seeking a ready food source like insects indoors. Using a portable blacklight at night can help locate them, as their exoskeletons fluoresce a bright greenish-yellow under ultraviolet light.
Safety Measures and What to Do If Stung
Preventative measures significantly reduce the risk of an encounter, especially during peak activity seasons. Sealing entry points around the home, such as cracks in foundations, walls, and poorly fitting window screens, helps keep scorpions outside. Removing potential outdoor hiding spots, including woodpiles, yard debris, and construction materials, eliminates their daytime shelter.
Inside the home, it is wise to shake out shoes, clothing, and towels before use, as scorpions may hide in these dark, confined spaces. Wearing shoes when walking outdoors at night, particularly around pool areas, is another simple safety step. Placing glass jars around crib or bed legs can prevent the climbing Bark Scorpion from accessing sleeping areas.
If a sting occurs and the scorpion was not the highly venomous Bark Scorpion, first aid is usually sufficient for symptom management. This involves:
- Cleaning the sting site with soap and water.
- Applying a cool compress to reduce pain and swelling.
- Keeping the affected limb elevated.
- Using over-the-counter pain relievers for minor discomfort.
If the sting is from a Bark Scorpion, or if severe symptoms develop, immediate action is necessary. Symptoms like difficulty breathing, muscle spasms, drooling, or abnormal eye movements require prompt medical evaluation. Contacting the Poison Control Center immediately is recommended, as their experts can guide the next steps and determine if hospital care is required.