Scorpions in Las Vegas: Where They Come From and How to Keep Them Out

Where did the Las Vegas scorpions come from?

The Arizona bark scorpion arrived in Southern Nevada around 1990 with plants imported from Arizona. New housing needed landscaping, and palm trees and other nursery stock came in by truck, carrying scorpions along. From those first colonies it spread through new track-home construction across the valley.

Las Vegas sits in the Mojave Desert, and the Arizona bark scorpion is a Sonoran Desert species. It was not part of the valley's original wildlife. The usual account, drawn from local news coverage and pest-industry sources, is that growth in the early 1990s brought in mature plants from Arizona, and the scorpions came with them.

That makes the bark scorpion a story about people more than about climate. A species that was not here a generation ago is now a regular household pest, because the valley built thousands of homes and landscaped them with imported plants. The same arrival route is documented for roof rats, which the roof rats in Las Vegas guide covers.

If you live in a neighborhood built after 1990, you live on ground that was cleared for the purpose. That is worth knowing because it explains why a scorpion problem can show up in a tidy, new, well-kept house.

Why do new neighborhoods have scorpion problems?

New construction disturbs desert ground and then replaces it with block walls, imported plants, irrigated beds and decorative rock. That mix gives scorpions shelter, moisture and prey close to houses. Per pest-industry sources, the bark scorpion spread through new track-home construction, so newer master-planned areas are not exempt.

Think about what a builder does to a desert lot. The native ground is graded flat. A slab goes in. A stucco house goes up. A perimeter block wall goes around the lot, and landscapers add palms, drip irrigation lines and gravel or decomposed granite. Each of those features can shelter insects, and scorpions follow their food.

Decorative gravel and rock groundcover can shelter scorpions and other pests, though that is a general pest-control observation more than a measured finding, so treat it as a likely factor and not a certainty. Drip lines add a reliable trickle of water in a dry yard, which draws crickets, roaches and other prey.

A 2000s stucco house in Mountain's Edge or Rhodes Ranch may be only a few years old, but it still has long block walls on both sides and a landscape designed to be lush. An older 1950s tract house in Charleston Heights has mature trees and aging walls instead. Both can host scorpions; the entry points are just different.

How is a hollow block wall a scorpion habitat?

A hollow concrete block wall is full of sealed-off air spaces, and bark scorpions can live in them in large numbers, entering through narrow cracks. Around Las Vegas, the species is more likely found on block walls and inside houses than in open desert. The wall is both home and highway.

Most valley block walls are built from concrete masonry units with hollow cores. Mortar joints crack with heat and settling, and the open top of a wall is often protected only by a cap that does not seal perfectly. A scorpion needs only a narrow gap to slip in. Inside the cores it finds shade, steady temperatures and the insects that wander in after it.

Walls also connect things. A wall that touches the house gives a scorpion a direct path to a stucco face, a weep screed or a gap at the base of a door. A wall beside a pool, a drip bed or a neighbor's yard links your property to theirs. So a scorpion you see in the house may have been living in the wall for months.

This is why stuccoing and capping hollow-block walls is one of the control measures in the pest-industry guidance. Closing the top and the joints removes living space instead of chasing animals that have plenty of it.

• Cracked mortar joints between blocks
• Gaps between the wall cap and the block below
• Open block cores at the wall's end or corner
• Spots where the wall meets the house stucco
• Weep holes and drainage gaps near the base

When are scorpions most active in Las Vegas?

Scorpion activity peaks in summer, climbs through spring into early fall, and goes inactive in winter. Spring and autumn are mating seasons, and September is one of the most active months. The trend follows heat, so a warm November evening is a very different risk from a July night.

Sightings begin to rise as the valley warms in spring. By July, when the average high is around 106 F, scorpions are at their peak. Activity stays high into September, which is among the most active months, and then drops off as nights chill in November.

Winter is not a free pass. Scorpions go inactive in the cold, but inactive does not mean gone. A scorpion sheltering in a wall cavity can still be inside the wall when spring arrives, so winter is a good time to seal gaps before the season returns.

Monsoon weather adds another wrinkle. Storms from July to mid-September can push pests toward higher, drier places, including houses. The monsoon pests guide looks at what changes after rain.

How do scorpions get into a Las Vegas house?

They enter through small gaps: worn door sweeps, loose weather stripping, window screens that do not fit, weep screeds at the base of stucco, gaps around pipes and cables, and cracks where a block wall meets the house. Bark scorpions are slim and flat, so a gap thin enough to be overlooked can be enough.

Walk the outside of your house and look at the places where two materials meet. The bottom of an exterior door is the classic one. A door sweep that has worn or bent leaves a gap you can sometimes see light through, and scorpions can use it.

Next, check the window screens. A screen that is torn or has a bent frame leaves an opening along one edge. Garage doors are another common entry, particularly at the corners and under the bottom seal.

Then look at the stucco base. A weep screed is the metal strip that lets moisture drain from behind stucco, and its slots can double as an entry if they are left open to the wall behind. Pipe and cable penetrations, dryer vents and the seam where a block wall abuts the house complete the list.

• Door sweeps and thresholds, including garage and patio doors
• Weather stripping around door frames
• Window screens that are torn, loose or ill-fitting
• Weep screeds and the base of the stucco
• Plumbing, cable and utility penetrations
• The joint between a block wall and the house

What does sealing a house against scorpions actually involve?

Sealing means closing the gaps scorpions use: tightening window screens, replacing weather stripping and door sweeps, caulking or foaming penetrations, and stuccoing and capping hollow-block walls. A technician usually walks the perimeter, notes each gap and works through them. A blacklight check at night can show where scorpions are active.

The job starts with an inspection. A technician looks at the doors, windows, stucco base and walls, often noting each gap. Because scorpions fluoresce under UV light, a night walk with a blacklight shows where they are moving, which helps decide where to spend the effort.

The repairs follow what the inspection found. Door sweeps and weather stripping are replaced or adjusted. Screens are tightened or refitted. Gaps around pipes and cables are filled with a suitable sealant. For hollow-block walls, the control advice is stuccoing and capping so the cores are not open to the sky.

Treatment and sealing do different jobs. Treatment lowers the number of scorpions you see; sealing changes whether they can get in. Most plans use both. For a description of the work, see scorpion exclusion and home sealing, and for treatment see scorpion control. The pest control cost guide lists sourced price estimates.

How do you find scorpions with a blacklight?

Scorpions fluoresce under UV light, so a handheld blacklight shows them as a bright blue-green glow in a dark yard. Check at night along block walls, around the house base and near door frames. A sighting tells you where activity is, not how many scorpions are present.

A UV flashlight is cheap and works because the scorpion's outer shell glows under ultraviolet light. Wait until it is fully dark, then walk slowly along the base of the block wall, the stucco line, the edges of gravel beds and the area around the patio door. Keep your hands and feet out of rock piles and under objects.

A blacklight is a finding tool, not a treatment. Seeing three scorpions in ten minutes does not tell you whether three or three hundred live in the wall. It does tell you where to look for the gap. Write down where you saw them, and give that to a technician. It saves time.

Wear closed shoes at night and shake out shoes and clothing that sit on the floor. If you or anyone in your home is stung, contact a clinician or Poison Control. The scorpion sting guide explains why this page does not try to judge a sting.

What should you do about scorpions in the yard and garage?

Reduce what shelters them and what feeds them. Pull stacked wood, boards and rock piles away from walls, trim vegetation off the house, and fix leaking irrigation. Seal the garage door bottom. These steps reduce hiding spots but do not replace sealing the house and capping hollow-block walls.

Scorpions look for shade and for insects. A woodpile against the house gives them both. So does a stack of pavers or a pile of leftover decorative rock. Moving these a few feet from the wall removes an easy place to hide near your door.

Vegetation that touches the house acts as a bridge. Trim shrubs back from the stucco and keep palm fronds trimmed away from the roofline. A drip line that leaks beside the wall gives crickets and roaches moisture, and the scorpions follow.

The garage deserves a special look. It is often the least sealed part of a valley house. Check the bottom seal on the garage door, the corners, and the door between garage and living space. Storage boxes on the floor give scorpions places to hide, so a shelf is better than a cardboard stack.