The bark scorpion, Centruroides sculpturatus, is the most commonly encountered and medically significant scorpion species found across the U.S. Southwest. This arachnid is responsible for human stings reported in states like Arizona and New Mexico. Despite its small stature, the bark scorpion generates concern due to the potency of its venom. Understanding dimensions and physical features of this scorpion is the first step toward effective identification.
Defining the Bark Scorpion’s Size
The physical size of the bark scorpion is a surprise to those expecting a large creature. Adult specimens typically measure between 1 and 3 inches (2.5 to 7.5 centimeters) in total length, placing them among the smaller scorpions in North America. Males tend to reach the upper end of this range, sometimes approaching 3.15 inches, while females are generally shorter.
An adult bark scorpion is roughly the length of a standard paperclip or the diameter of a quarter. This diminutive size is a major factor in their ability to inhabit small crevices and enter homes undetected. Juvenile scorpions are even smaller, sometimes measuring less than an inch, which makes them exceedingly difficult to spot.
Unique Physical Characteristics for Identification
Beyond simple measurements, several distinguishing characteristics separate the bark scorpion from other, often larger, less harmful species. The overall coloration is usually a pale yellow, straw color, or light tan, which provides excellent camouflage against desert rock and sand. This uniform, translucent appearance means they lack the darker, more robust coloration seen on many other desert scorpions.
A more telling feature is the body shape, which is noticeably slender, including the tail (metasoma) and the pincers. The thin tail is a signature trait that contrasts sharply with the thick tails of many larger scorpions found in the same arid regions. The bark scorpion also exhibits a unique resting posture that is characteristic of the species.
When stationary, the tail is held coiled to the side of the body, resting parallel to the surface, rather than being arched straight up and over the back like most other scorpions. This species is one of the few capable of climbing vertical surfaces, such as stucco walls and trees, due to specialized structures on their legs. They also exhibit negative geotaxis, meaning they prefer an upside-down orientation when resting, such as on the underside of a rock or log.
Typical Habitat and Geographic Range
The geographic range of the bark scorpion is centered in the Sonoran Desert, primarily covering Arizona, but also extending into parts of western New Mexico, southern Nevada, and the extreme southeastern edge of California. They thrive in arid environments but prefer areas that offer some moisture, such as riparian habitats near water sources.
To avoid intense daytime heat, their small, slender bodies enable them to seek refuge in very narrow spaces. Outside, they are commonly found hiding in the following locations:
- Beneath loose tree bark.
- In rock crevices.
- Under wood piles.
- Within the cracks of block wall fences.
Their ability to climb allows them to inhabit vertical spaces, including the fronds of palm trees.
This preference for tight spaces translates into their presence in human dwellings, as they can squeeze through openings as small as 1/16 of an inch to seek cooler, darker conditions. Once indoors, they hide in wall voids, dark closets, or shoes, and are often found trapped in sinks or bathtubs after falling in while hunting at night.