Behavior: how the bark scorpion lives

Can bark scorpions really climb walls?

Yes. Centruroides is the only scorpion genus in the Southwest that climbs smooth vertical surfaces, including stucco, block, tree bark, and even interior walls and ceilings, and it routinely rests on ceilings and the undersides of eaves.^[1][4] This is the single behavior that most separates it from the other Arizona species and the reason it reaches upper floors, hangs from ceilings, and drops from vents. It cannot climb clean, smooth glass or glazed tile reliably, which is the basis of the glazed-tile perimeter barriers tested by UArizona researchers.^[1]

Why is it always upside down?

Negative geotaxis: given a vertical surface, bark scorpions orient head-down.^[2] Combined with thigmotaxis, the preference for contact on several sides of the body, this puts them under overhangs, inside the top of a block wall, behind the lip of a weep screed, and under the rim of a pool skimmer lid.^[1][2]

How small a gap will it use?

In laboratory choice tests it preferred crevices around 14 mm wide, oriented vertically, and 95% of the animals chose block-wall-style refuges over the alternatives.^[1][2] An adult can pass through a 1.6 mm (1/16 inch) opening.^[4] This is why "seal the house" is the core of every extension recommendation.^[5]

When is it active?

At night, from spring through fall, and specifically once overnight lows stay above about 77°F (25°C), per UArizona Extension.^[3] Activity peaks in the hot, humid nights of the monsoon; the FEARS study found rain preceded 62.5% of summer stings versus 11.1% of winter stings.^[6] Poison-center data show envenomations peak in August and September.^[7] In winter it retreats to sheltered crevices and is rarely seen.

What is "stilting"?

When a surface is very hot or carries insecticide residue, bark scorpions raise their bodies high on extended legs, minimizing contact.^[1] Researchers cite this as one reason perimeter sprays often disperse scorpions rather than kill them.^[1]

Are they solitary?

Mostly, but not strictly. Bark scorpions are described as quasi-social: they tolerate one another at good shelter sites, and a single structure can yield dozens to hundreds over a season, especially in the cool months when they aggregate.^[1] They are also cannibalistic, so "social" is relative.^[1] Established populations move little from night to night when a good crevice already supplies food and shelter.^[1]

How does it find its way in the dark?

By vibration and touch far more than by sight. It has a pair of median eyes and clusters of lateral eyes, but it hunts with fine sensory hairs on the pedipalps and legs and with the pectines, comb-like organs on the underside that read surface texture and chemistry.^[8][9] Tarsal hygroreceptors let it sense humidity, which helps explain its attraction to irrigated ground.^[1]