Arizona Bark Scorpion

The **Arizona bark scorpion** (*Centruroides sculpturatus*, included in *Centruroides exilicauda*) 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).

## Predators

The **Arizona bark scorpion** (*Centruroides sculpturatus*, included in *Centruroides exilicauda*) 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). Bark scorpions are eaten by a wide variety of animals such as birds (especially owls), reptiles, and other vertebrates. 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.

## Life Cycle

Arizona bark scorpions have a gestation period of several months, are born live, and are gently guided onto their mother's back. The female usually gives birth to anywhere from 25 to 35 young. These remain with their mother until their first molt, which can be up to 3 weeks after birth. Arizona bark scorpions may live up to 6 years. 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.

## Habitat

The bark scorpion is particularly well adapted to the desert: layers of wax 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. *Centruroides* 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.

## Venom

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 and 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.

**Antivenom**

An antivenom was developed for this species at Arizona State University by Dr. Herbert L. Stahnke, and produced in quantities sufficient to treat individuals within the state of Arizona. This antivenom was not FDA approved, but use within the state of Arizona was allowable and very successful in shortening the duration of symptoms and hospitalization. Production of this antivenom ceased by 2000 and the product was unavailable by 2004. A Mexican-produced antivenom, Anascorp [Antivenin Centruroides (scorpion) F(ab′)2, Laboratorios Silanes, Instituto Bioclon SA de CV], received FDA approval on August 3, 2011, and is now in use.

**First Aid**

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 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.