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Western black widow

Latrodectus hesperus
Also called black widow

This is the most medically important spider in the western states; a bite from an adult female can cause severe muscle pain and cramps, so get medical advice right away.

If you think you were bitten or stung, call Poison Help. Free, private, any hour.1-800-222-1222Call 911 for trouble breathing, swelling of the face or throat, or severe symptoms.
Western black widow, photo 1
Photo: Chris Stahl, CC BY 4.0, via iNaturalist
SizeAdult female body about 8–13 mm (about 1/3 to 1/2 inch), around 1.5 inches with legs spread; males much smaller, about 3–8 mm (1/8 to 1/3 inch)
Where in the houseGarage, basement, outside near the house, windows and walls
WhenMost active late spring through fall; adults and young can overwinter in garages and crawl spaces.

Check these features

  1. Adult female is shiny black (sometimes dark brown) with a large, round abdomen
  2. Red to orange hourglass on the underside, sometimes broken into spots or a bar
  3. Males and young are tan or gray with white, cream, orange or red stripes and spots
  4. Untidy, tangled, strong web low to the ground with a retreat in a hole or crack
  5. Smooth, round to teardrop-shaped cream or tan egg sac

Bites and stings

The bite is often painless or feels like a pinprick and may leave a small red mark. Within about an hour, pain can spread with muscle cramps (often a hard, rigid belly), sweating, nausea, restlessness or chest tightness. Symptoms usually peak in the first day and ease over a few days, but can linger. Get medical advice right away for any suspected bite; young children, older adults, pregnant people and anyone with heart or breathing problems should be seen promptly.

What to do

  1. Move away from the spider, then wash the bite with soap and water and apply a cool, damp cloth or wrapped ice.
  2. Call Poison Help at 1-800-222-1222 (US, free, any hour) for advice on what to do next.
  3. Call 911 for trouble breathing, swelling of the face or throat, or severe symptoms such as spreading pain, chest tightness or strong muscle cramps.
  4. If it is safe, photograph the spider or trap it in a jar for identification; do not handle it bare-handed.
  5. Do not cut the bite or try to remove venom.

Look-alikes

False black widow (Steatoda grossa)Dull brown to purplish-black with no red hourglass; very common indoors along the Pacific Coast.
Brown widowMottled tan-brown with an orange hourglass and a spiky egg sac; in the West mainly in urban southern California.
Southern and northern black widowsLook almost the same; they mainly live in the eastern and central states.

Why it came inside

It lives around foundations, woodpiles, rock walls, meter boxes and sheds, and wanders into garages, crawl spaces and basements, often near doors, vents and window wells, especially as the weather cools.

Keep it out

  • Wear gloves when handling firewood, rocks, irrigation or meter boxes, and stored items.
  • Shake out shoes, gloves and clothes left in garages before wearing them.
  • Clear clutter from crawl spaces, garages and window wells, and keep woodpiles away from the house.
  • Fit door sweeps, repair screens and seal cracks around the foundation and entry points.
  • Vacuum webs and egg sacs and point outdoor lights away from doors to attract fewer insects.

What helps

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Sticky traps

Flat glue traps set along walls and in corners show what is moving through and where. Place them where pets and children can't reach.

See options on Amazon
Door sweep

Closes the gap under an exterior door. If you can see daylight under the door, bugs can get in.

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Caulk and sealant

Silicone or siliconized acrylic caulk closes cracks around windows, pipes and baseboards. Bigger gaps need foam backer rod or expanding foam first.

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Screen repair kit

Patches or replaces torn window and door screens, one of the most common ways insects get in.

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Weatherstripping

Seals the gaps around doors and windows that let in drafts and bugs alike.

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Vacuum with a hose

Lets you remove bugs, webs and egg sacs without touching them. Empty the bag or canister outside right away.

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Bug catcher

A long-handled catcher moves a spider or insect outside without you having to touch it.

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UV flashlight

Scorpions glow under ultraviolet light, which makes them much easier to spot at night.

See options on Amazon

Sources

  1. University of California IPM
  2. Colorado State University
  3. Washington State Department of Health
  4. Montana State University Extension
  5. Utah State University Extension
  6. Washington State University Extension

Checked October 18, 2026. Rating backed by 4 sources. How we rate danger.