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How to identify it
- Females are 7 to 8 mm long and males about 6 mm (roughly 1/4 to 5/16 inch). Penn State describes the body as pale tan or yellow with a gray mark in the middle of the front body section; Bohart describes most cellar spiders as whitish gray with darker markings at the leg joints.[1][3]
- The abdomen is cylindrical and about three times as long as it is wide. An adult female's front legs are about 50 mm, roughly 2 inches, long.[1]
- It hangs upside down in loose, irregular webs in dark, quiet places such as cellars, crawl spaces, garages and room corners.[1][6][5][3]
- When disturbed it vibrates or bounces in the web so fast that it becomes a blur; Bohart says some look like they are doing pushups.[1][3][6]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Harvestmen (true daddy-longlegs) | Harvestmen are arachnids in a separate order (Opiliones), not spiders: they have no venom glands, make no silk, and their body isn't clearly divided into two parts. Cellar spiders are true spiders that spin webs.[6][3] |
| Marbled cellar spider (Holocnemus pluchei) | A related cellar spider with a black underside. UC IPM says it was introduced into California in the 1970s and has since displaced the longbodied cellar spider there.[3][2] |
| Common house spider | Also builds cobwebs in room corners and windows, but lacks the cellar spider's extremely long, thin legs.[2][1] |
Where it lives
The most common cellar spider in the United States, found in buildings throughout the year; in California the marbled cellar spider has largely replaced it.[1][2]
Biology and life cycle
Both sexes live in heated buildings all year. It takes about a year to mature, and adults can live two years or more.[1]
Females lay 25 to 60 eggs about 1 mm across, wrap them in a thin layer of silk, and carry the bundle in their jaws until the eggs hatch.[1][6][3]
They eat large numbers of small insects, especially mosquitoes, midges and other small flies, and the Connecticut Agricultural Experiment Station notes they also catch other spiders.[3][5]
They often gather in groups near each other, though they aren't social.[3]
In a 2002 survey of 50 Kansas houses, cellar spiders and two cobweb spiders were found preying on brown recluse spiders, but the author concluded they offer little real chance of controlling recluses.[7]
Damage and signs
Health risk
Penn State says cellar spiders aren't known to bite people. Bohart and the Connecticut Agricultural Experiment Station say their mouthparts are too small to puncture human skin, while UC IPM puts it more cautiously: their fangs are too short to pierce skin in most cases. The story that they have one of the most potent spider venoms is a myth; Bohart says venom studies show it is no more potent than any other spider's.[1][3][5][2]
Control
Prevention
Outdoor lights attract insects that draw spiders, so keep fixtures away from windows and doorways where possible.[2]
Keep them out
Caulk cracks, seal windows, screen vents and keep screens and doors tight to keep out spiders and the insects they eat. A dehumidifier and fixing leaks also make basements less inviting.[2][5][6]
Sanitation
Reduce clutter in garages, sheds, crawl spaces and basements, and keep stored boxes sealed, off the floor and away from walls.[2][6]
Traps and physical control
Vacuum spiders and webs from corners, windows, basements and storage areas; UC IPM says vacuumed spiders usually don't survive. If you'd rather keep the spiders, the Connecticut Agricultural Experiment Station suggests tapping the switched-off vacuum nozzle against the web first so the spider leaves before you clear it.[2][5]
Biological control
The Connecticut Agricultural Experiment Station calls cellar spiders good pest controllers indoors and suggests tolerating them in basements, cellars and bathrooms.[5]
Pesticides
Sources differ on sprays. UC IPM says insecticides give only temporary control unless paired with housekeeping and that vacuuming or crushing the spider is just as easy. Colorado State says residual insecticides in corners can control spiders, but only alongside removing the places they live.[2][6]
Common questions
- Is a cellar spider a daddy longlegs?
- It's often called one, but true daddy-longlegs are harvestmen, which aren't spiders. Cellar spiders are true spiders with very long legs.[3][6]
- Are cellar spiders the most venomous spiders?
- No. That's an urban myth; venom studies show it is no more potent than other spiders' venom, and their mouthparts are too small to puncture human skin.[3][5]
- Why do cellar spiders shake in their webs?
- When threatened they vibrate rapidly in the web, which makes them hard to see.[1][3][6]
- Should I get rid of cellar spiders in the basement?
- You don't have to. They eat mosquitoes, flies and other spiders, and the Connecticut Agricultural Experiment Station suggests leaving them in basements and cellars; clear old webs with a vacuum if they bother you.[5][3]
Sources
- Penn State Extension, “Longbodied Cellar Spider (updated January 19, 2026).” extension.psu.edu/longbodied-cellar-spider (accessed 2026-11-11)
- University of California Statewide IPM Program, “Spiders (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/spiders/ (accessed 2026-11-11)
- Bohart Museum of Entomology, University of California, Davis, “Cellar Spiders (Information No. 36).” bohart.ucdavis.edu/sites/g/files/dgvnsk4616/files/media/documents/note_36_cellar_spider.pdf (accessed 2026-11-11)
- iNaturalist, “Pholcus phalangioides taxon page (order and family).” www.inaturalist.org/taxa/67328 (accessed 2026-11-11)
- The Connecticut Agricultural Experiment Station, “Spiders Found in the House (G. E. Ridge and K. Dugas).” portal.ct.gov/-/media/caes/documents/publications/fact_sheets/entomology/spiders_in_the_house.pdf (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)
- Journal of Economic Entomology, via PubMed, “Sandidge J (2004), Predation by cosmopolitan spiders upon the medically significant pest species Loxosceles reclusa (Araneae: Sicariidae): limited possibilities for biological control, Journal of Economic Entomology 97(2):230-234.” pubmed.ncbi.nlm.nih.gov/15154440/ (accessed 2026-11-11). Cited from the PubMed abstract.