Can Scorpions Climb Walls? How Bark Scorpions Climb and Hide

Which scorpions can climb walls?

Climbing ability varies widely among the more than 2,500 scorpion species. In North America, the best climbers are the bark scorpions of the genus Centruroides, including the Arizona bark scorpion of the Sonoran Desert and the striped bark scorpion found from New Mexico through Texas to Kansas and Missouri. In the deserts of the American Southwest, Centruroides is the only genus that regularly climbs walls and trees.

Many tropical scorpions are also good climbers. They live on tree trunks, under bark and among plants rather than in burrows. By contrast, large burrowing species such as the giant desert hairy scorpion, the emperor scorpion of West Africa and many sand-living desert scorpions spend most of their time on or under the ground and rarely climb far.

The difference often shows in body shape. Climbing scorpions tend to be slim and light, with thin legs, slender pincers and a long, thin tail. Burrowers are heavier, with thick pincers and stout legs built for digging and grabbing.

How do scorpions climb?

Scorpions have no sticky pads like geckos or tree frogs. Instead, each leg ends in a pair of small curved claws, and the legs carry stiff bristles and spines. On a rough surface, the claws hook into tiny bumps, cracks and pores, while the bristles add extra grip. A light body helps: the lighter the animal, the less force each claw has to hold.

That system works well on:

• tree bark, wood and wooden fences
• stucco, brick, concrete block and unpolished stone
• rough plaster, rough paint and textured ceilings
• fabric, such as curtains and bedding

It works poorly on smooth surfaces. Glass, glazed tile, polished metal, smooth plastic and glossy porcelain offer almost no edges for the claws, so scorpions slip. This is why bark scorpions found in bathtubs or sinks usually cannot climb back out, and why a glass jar is enough to hold a scorpion.

Why do bark scorpions rest upside down?

Bark scorpions show a behavior scientists call negative geotaxis: they prefer to orient themselves against gravity, which often means hanging upside down. During the day they cling to the underside of loose bark, stones, boards, ledges, patio furniture and roof beams.

Hanging out of sight protects them from predators such as birds and lizards, and keeps them out of direct sun. It also explains many stings: a person reaches under a board, a flowerpot or a ledge without seeing the scorpion clinging there. Bark scorpions also hide in shoes, gloves and folded clothing, and they can drop from ceilings onto floors or beds.

Where do bark scorpions hide during the day?

Bark scorpions are nocturnal. In the heat of the day they look for cool, slightly humid shelters, including:

• under loose tree bark, especially on mesquite, cottonwood and palm trees
• beneath rocks, boards, wood piles and garden debris
• inside cracks in block walls and stucco
• in roof spaces, wall voids and garages
• in shoes, clothing and towels left on the floor

They can slip through very narrow gaps, around 1.6 mm (1/16 in) wide, because their bodies are flat and flexible. At night they come out to hunt crickets, cockroaches and other insects on walls, tree trunks and the ground, often sitting still and waiting for prey to pass.

Why do bark scorpions cluster in winter?

In the cooler months, from about late fall to early spring, bark scorpions become less active and often gather in groups. These clusters, from a few to a few dozen scorpions, form in sheltered crevices, under bark, in wood piles or inside walls.

Scientists think clustering helps the scorpions save water and possibly heat by reducing the body surface exposed to dry air, but the exact benefits are still being studied. It is unusual behavior for scorpions, most of which live alone and may even eat one another. In spring, the groups break up and the scorpions disperse to hunt. This is also when people notice more bark scorpions on walls.

Can other scorpions climb at all?

Even poor climbers can manage low, rough obstacles such as rocks, curbs and tree roots. What sets bark scorpions apart is their ability to go vertical for long distances and to walk upside down on ceilings and bark.

Scorpions are also good at squeezing into small spaces, which matters more than climbing for many species. Burrowing scorpions dig their own tunnels in sand or soil, while others use rodent burrows or spaces under stones. Whether a scorpion climbs or burrows, the aim is the same: to escape heat, dry air and predators during the day.

How to spot climbing scorpions safely

Bark scorpions are hard to see by day, but like nearly all scorpions they glow blue-green under ultraviolet light. With a UV flashlight, people in Arizona can often spot them on walls and tree trunks at night from a distance of a meter or two. Learn more in why scorpions glow under UV light.

Look, but never touch. The Arizona bark scorpion is the most venomous scorpion in the United States, although deaths are now very rare; read more in is the Arizona bark scorpion deadly?. If anyone develops severe symptoms after a sting, seek emergency medical help immediately or call 911.