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Harmless

Woodlouse spider

Dysdera crocata
Also called woodlouse hunter, sowbug killer, pillbug hunter, slater spider

Not dangerous: the big forward-pointing fangs look scary, but bites are rare and usually just sting briefly or itch.

Woodlouse spider, photo 1
Photo: Joss Carr, CC BY 4.0, via iNaturalist
SizeFemales 11–15 mm (about 1/2 inch); males 9–10 mm (about 3/8 inch)
Where in the houseBasement, garage, bathroom, outside near the house
WhenMost often seen in spring and summer; indoor wanderers may also turn up in late summer and fall.

Check these features

  1. Shiny dark red to orange-red front body and legs
  2. Smooth, plain cream, gray or tan abdomen with no pattern
  3. Very large fangs that stick straight out in front of the head
  4. Six eyes in a tight oval group
  5. Found under bricks, stones, logs, mulch or damp boxes, often near pill bugs

Bites and stings

Rarely bites, but it can nip if picked up or pressed against skin. A bite usually causes brief pain and a small, itchy red spot that fades without treatment. Wash the area, use a cold pack, and get medical advice if redness spreads, the spot looks infected, or you have signs of an allergic reaction.

What to do

  1. Don't pick it up with bare hands; scoop it into a cup or jar with a card and release it outside.
  2. If bitten, wash the spot with soap and water and apply a cold pack.
  3. Vacuum any you find indoors if you prefer not to relocate them.
  4. If you see many, look for damp areas and pill bugs near the foundation, since that is what draws them.

Look-alikes

Brown recluseA recluse is a soft uniform tan with a dark violin mark on its front body and small fangs, while the woodlouse spider has a glossy red front body with no marking, a pale plain abdomen and huge, forward-pointing fangs.
Hobo or funnel weaver spidersFunnel weavers are brown with patterned abdomens and long hairy legs, and they build sheet webs; the woodlouse spider is red and cream, smooth, and builds no capture web.
Ground or sac spidersOther small hunters may be pale or brown, but none combine the bright red-orange front half with oversized protruding fangs.

Why it came inside

It hunts pill bugs and sow bugs in damp spots, so it follows them in from mulch, woodpiles and foundation areas, especially where basements or crawl spaces stay moist.

Keep it out

  • Reduce moisture in basements and crawl spaces; a dehumidifier helps.
  • Move mulch, leaf litter, woodpiles and stones back from the foundation.
  • Seal foundation cracks and gaps with caulk and fit tight door sweeps.
  • Place sticky traps along basement walls from late summer through fall to catch wanderers.
  • Control pill bugs and sow bugs around the house, which removes the spider's food.

What helps

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Dehumidifier

Keeping a basement at about 50 percent humidity or lower makes it less welcoming to the bugs that need damp air.

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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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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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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.

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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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Sources

  1. Utah State University Extension
  2. University of California Agriculture and Natural Resources
  3. Penn State Extension
  4. University of Minnesota Extension

Checked October 18, 2026. Rating backed by 3 sources. How we rate danger.