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How to identify it
- Females are 5 to 6 mm long, with a yellowish-brown front body and a dirty-white to brown, rounded abdomen marked with gray chevrons; some have a triangular black spot on top of the abdomen. The legs are yellow with darker rings at the end of each segment.[1]
- Males are smaller, 3.8 to 4.7 mm, with orange legs.[1]
- Like other cobweb spiders it has a bulbous abdomen and hangs upside down in an irregular, sticky web.[3][4]
- Egg sacs are brown, oval and papery, 6 to 9 mm across.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Black widow | A relative in the same cobweb family, but shiny black with a red hourglass under the abdomen and found mostly outdoors and in garages.[3][5][4] |
| False widows (Steatoda) | Also cobweb spiders, but generally black, with a pale band across the front of the abdomen and no red hourglass underneath.[4] |
Where it lives
Found through most of the world. It is extremely common in houses and barns, most often in damp basements and crawl spaces, and outdoors under rocks and boards and beneath bridges.[1][2]
Biology and life cycle
Males and females can be found at any time of year and live together in the web, mating repeatedly. Some live a year or more after maturing.[1]
A female may make twelve or more egg sacs over her life, each with 140 to 380 eggs; once mated, she lays eggs periodically, and the life cycle is relatively short.[1][6]
It often abandons a web and builds a new one nearby, which is why webs seem to multiply.[1]
Damage and signs
Health risk
Physicians' and entomologists' reviews name only widow and recluse spiders as medically important in North America, and say most other spiders involved in verified bites cause minor, short-lived effects.[7][8][9]
Control
Keep them out
Caulk cracks around the foundation, keep screens and doors tight, and move outdoor lights off the house or switch to yellow or sodium vapor bulbs, which draw fewer of the insects spiders eat.[2][4]
Sanitation
Vacuum or brush webs and egg sacs regularly. A dusty web is an old one the spider has left, since occupied webs are kept clean.[2][4]
Remove clutter, woodpiles, leaf litter and heavy vegetation near the foundation, keep crawl spaces clear, and store boxes off the floor; vacuumed spiders usually don't survive.[2][4]
Traps and physical control
Sticky traps along baseboards catch wandering spiders, and a single spider can be caught under a jar and released outdoors.[2][4]
Pesticides
UC IPM says insecticides don't give long-term spider control and generally shouldn't be used outdoors; Colorado State says residual pyrethroid sprays can help in corners where spiders breed, but foggers have little effect.[2][4]
A spider in the laboratory
The common house spider has become a laboratory animal for studying how body plans develop and evolve. It has a relatively short life cycle, and a mated female keeps laying eggs at intervals.[6]
Its sequenced genome revealed a whole-genome duplication in the spider lineage, which researchers use to study how duplicated genes contribute to animal diversity.[6]
Where sources disagree
Sprays: UC IPM says insecticides give no long-term control, work only if you hit the spider, and shouldn't generally be used outdoors, while Colorado State says residual pyrethroid sprays can be used in corners and other sites where spiders breed. UC IPM adds that spraying is only temporary without housekeeping, and Colorado State that foggers have little effect.[2][4]
Common questions
- Why do cobwebs keep coming back?
- House spiders often abandon a web and build a new one nearby, so one spider can make many webs. Dusty webs are abandoned ones.[1][2]
- Does the common house spider bite?
- Rarely. Penn State points out that bites are scarce in the literature even though the spider lives in so many houses.[1]
- Should I spray for house spiders?
- Usually not. Vacuuming webs, sealing gaps and cutting back outdoor lighting work better; UC IPM says sprays give only temporary control without housekeeping.[2][4]
Sources
- Penn State Extension, “Common House Spider.” extension.psu.edu/common-house-spider (accessed 2026-11-11)
- University of California Statewide IPM Program, “Pest Notes: Spiders, Publication 7442.” ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pnspiders.pdf (accessed 2026-11-11)
- University of Kentucky Entomology, “ENTFACT-622: Common Spiders Found Around Homes and Buildings.” entomology.mgcafe.uky.edu/ef622 (accessed 2026-11-11)
- Colorado State University Extension, “Spiders in the Home (fact sheet 5.512).” extension.colostate.edu/topic-areas/insects/spiders-in-the-home-5-512/ (accessed 2026-11-11)
- University of California Statewide IPM Program, “Pest Notes: Widow Spiders and Their Relatives, Publication 74149 (revised March 2017).” ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pnblackwidow.pdf (accessed 2026-11-11)
- EvoDevo, via PubMed, “Oda and Akiyama-Oda (2020), The common house spider Parasteatoda tepidariorum.” pubmed.ncbi.nlm.nih.gov/32206294/ (accessed 2026-11-11)
- Critical Care Nursing Clinics of North America, via PubMed, “Vetter (2013), Spider envenomation in North America.” pubmed.ncbi.nlm.nih.gov/23692939/ (accessed 2026-11-11)
- Annual Review of Entomology, via PubMed, “Vetter and Isbister (2008), Medical aspects of spider bites.” pubmed.ncbi.nlm.nih.gov/17877450/ (accessed 2026-11-11)
- American Family Physician, via PubMed, “Herness, Snyder and Newman (2022), Arthropod bites and stings.” pubmed.ncbi.nlm.nih.gov/35977137/ (accessed 2026-11-11)
- iNaturalist, “Parasteatoda tepidariorum taxon page (order and family).” www.inaturalist.org/taxa/120583 (accessed 2026-10-06)