The Arizona bark scorpion (Centruroides sculpturatus) is a small light brown scorpion common to the Sonoran Desert in southwest United States and northwestern Mexico. An adult male can reach 8 cm in length (3.14 inches), while a female is slightly smaller, with a maximum length of 7 cm (2.75 inches).
The bark scorpion is nocturnal and prefers to ambush its prey, usually feeding on crickets, roaches, beetles, and other small insects. Bark Scorpions can also be cannibalistic, occasionally feeding on a fellow scorpion.
Bark scorpions are eaten by a wide variety of animals such as birds, reptiles, and other invertebrates. Some examples include spiders, snakes, peccaries, rodents, and other scorpions. Development, pesticides and collecting scorpions for research or the pet trade also reduces the bark scorpion population.
The painful and potentially deadly venom of bark scorpions has little effect on grasshopper mice. Scientists have found the scorpion toxin acts as an analgesic rather than a pain stimulant in grasshopper mice.
While nearly all scorpions are solitary, the Arizona bark scorpion is a rare exception: during winter, packs of 20 to 30 scorpions can congregate.
Bark scorpions, like most other scorpions, are incredibly resilient. During US nuclear testing, scorpions, along with cockroaches and lizards, were found near ground zero with no recorded adverse effects.
The bark scorpion is particularly well adapted to the desert: layers of fat on its exoskeleton make it resistant to water loss. Nevertheless, bark scorpions hide during the heat of the day, typically under rocks, wood piles, or tree bark. Bark scorpions do not burrow, and are commonly found in homes, requiring only 1/16 of an inch for entry.
Arizona bark scorpions prefer riparian areas with mesquite, cottonwood, and sycamore groves, all of which have sufficient moisture and humidity to support insects and other prey species. The popularity of irrigated lawns, and other systems which increase environmental humidity in residential areas, has led to a massive increase in the number of these animals in some areas.
Centuroides scorpions are unusual in that they are the only genus in the southwest that can climb walls, trees, and other objects with a sufficiently rough surface. Bark scorpions practice negative geotaxis, preferring an upside down orientation, which often results in people being stung due to the scorpion being on the underside of an object.
The bark scorpion is the most venomous scorpion in North America, and its venom can cause severe pain (coupled with numbness, tingling, and vomiting) in adult humans, typically lasting between 24 to 72 hours. Temporary dysfunction in the area stung is common; e.g. a hand or possibly arm can be immobilized or experience convulsions. It also may cause loss of breath for a short time. Due to the extreme pain induced, many victims describe sensations of electrical jolts after envenomation.
Fatalities from scorpion envenomation in the USA are rare and are limited to small animals (including small pets), small children, the elderly, and adults with compromised immune systems. Extreme reaction to the venom is indicated by numbness, frothing at the mouth, paralysis, and a neuromotor syndrome that may be confused with a seizure and that may make breathing difficult, particularly for small children. Two recorded fatalities have occurred in the state of Arizona since 1968; the number of victims stung each year in Arizona is estimated to be in the thousands. In Mexico, more than 100,000 people are stung annually, and during a peak period in the 1980s, the bark scorpion claimed up to 800 lives there.
Basic first aid measures can be used to help remediate scorpion stings:
- Clean sting site with soap and water
- Apply a cool compress (cool cloth)
- Take acetaminophen (also known as paracetamol) or ibuprofen for local pain and swelling
Since the amount of venom a scorpion injects varies, Arizona poison control centers suggest immediate medical attention only in the event of extreme pain or stings involving weaker individuals.
Bark scorpions, like most other scorpions, will glow when exposed to a blacklight. This is particularly useful in scorpion detection, since bark scorpions are active during the night, and can be easily spotted using this method. Typical UV LED flashlights enable their human operator to readily detect scorpions at a distance of approximately 6 feet. Newly molted scorpions will not glow under ultraviolet light for a few days after molting.