Cellar spiders are easy to get rid of because they depend on specific conditions: darkness, moisture, and a steady supply of small insects. Remove those conditions and the spiders leave or die off. For immediate results, you can vacuum up the spiders, their webs, and their egg sacs directly, then follow up with environmental changes that keep them from coming back.
Why Cellar Spiders Move In
Cellar spiders (the long-legged, wispy spiders you see hanging upside down in corners) gravitate toward undisturbed, low-light areas with higher humidity. Basements, crawl spaces, garages, and closets are ideal. They build messy, irregular webs in ceiling corners and along walls, then wait for prey to stumble in.
Their diet is almost entirely other small creatures: flies, mosquitoes, gnats, ants, and even other spiders. Females have been observed invading another spider’s web, eating the resident spider, and then using the stolen web to catch new prey. If you’re seeing cellar spiders, it means there’s a food supply nearby. A damp basement that attracts gnats or drain flies is essentially a buffet.
Vacuum Them Out First
The fastest way to clear cellar spiders is a vacuum with a hose attachment. Sweep it across ceiling corners, behind furniture, along floor joists, and around window frames. This removes the spiders, their webs, and their egg sacs in one pass. Cellar spiders carry their egg sacs in their jaws, so catching the spider usually means catching the next generation too. Empty the vacuum bag or canister into a sealed bag and toss it outside immediately.
Repeat this once a week for a few weeks. Cellar spiders don’t move much and they rebuild webs in the same spots, so consistent removal disrupts their ability to feed and reproduce. On its own, vacuuming won’t solve the problem permanently, but it gives you a clean starting point while you address the conditions that attracted them.
Drop the Humidity Below 50%
Moisture is the single biggest factor. Cellar spiders thrive in damp environments, and so do the insects they eat. Running a dehumidifier in your basement to keep humidity between 30% and 50% makes the space less hospitable for both the spiders and their prey. If you don’t have a hygrometer (a small humidity gauge), inexpensive digital models cost a few dollars and let you monitor conditions over time.
Beyond a dehumidifier, check for water intrusion. Fix leaky pipes, patch foundation cracks where moisture seeps in, and make sure your dryer vent exhausts outside rather than into the basement. If you have exposed dirt in a crawl space, a vapor barrier (plastic sheeting over the floor) cuts moisture significantly. Improving airflow with a fan also helps dry out stagnant corners where spiders like to set up.
Cut Off Their Food Supply
Cellar spiders stay where the food is. If you reduce the population of small insects in your home, the spiders lose their reason to be there. A few practical steps make a big difference:
- Fix drain issues. Drain flies breed in the organic buildup inside floor drains and sink drains. Clean these regularly with a stiff brush and flush them with water.
- Manage trash and recycling. Fruit flies and gnats breed in food waste. Keep bins sealed and take them out frequently.
- Switch exterior lighting. Standard white bulbs near doors attract flying insects, which then find their way inside. Yellow “bug light” bulbs or sodium vapor lights draw far fewer insects.
- Address houseplant soil. Fungus gnats breed in damp potting soil. Let the top inch of soil dry out between waterings.
Seal Entry Points
Spiders and insects can fit through gaps as small as 1/16 of an inch. A thorough sealing job around your home’s exterior keeps new ones from getting in. Start with the most common entry points:
Check under all exterior doors. Lie on the floor and look for light coming through. If you see any, install door sweeps or thresholds and run a bead of caulk along the bottom outside edge of the threshold. Garage doors need a rubber bottom seal (vinyl cracks in cold weather and stops sealing properly). Sliding glass doors can be sealed by lining the bottom track with half-inch to three-quarter-inch foam weatherstripping.
Seal every utility opening where pipes, wires, or vents pass through your foundation or siding. This includes outdoor faucets, electrical outlets, gas meters, dryer vents, and cable lines. Use silicone or acrylic latex caulk for small gaps. For larger holes around pipes, expandable foam, steel wool, or copper mesh works well. Caulk around all window frames, door frames, and fascia boards with a good quality silicone or acrylic latex product.
Do Natural Repellents Work?
Peppermint oil is the most commonly recommended natural spider repellent online, but the scientific evidence is lukewarm. A study published in the Journal of Economic Entomology tested peppermint oil, lemon oil, and chestnuts against three spider species. Peppermint oil repelled two of the three species in more than 75% of choice tests, but had no significant effect on the third. Lemon oil, despite being the most popular recommendation in online searches, had no significant repellent effect on any of the species tested.
No cellar spiders were included in that particular study, so there’s no direct evidence that peppermint oil works on them specifically. If you want to try it, dilute 15 to 20 drops of peppermint essential oil in a spray bottle of water and apply it to corners and entry points. It won’t hurt, and the effect on some spider species is real, but don’t rely on it as your primary strategy. Environmental changes are far more reliable.
When to Consider Residual Sprays
For persistent problems, a residual insecticide applied along baseboards, in corners, and around window frames can kill spiders on contact and continue working for weeks. Look for products labeled for indoor spider control at hardware stores, typically containing pyrethroids. Apply them in cracks, crevices, and the corners where you see web activity, not as a broadcast spray across open surfaces.
Sticky traps placed along walls and in corners can also catch cellar spiders and help you gauge how active the population is. They’re especially useful for monitoring whether your other efforts are working. If you’re still seeing heavy web buildup and dozens of spiders after a few weeks of vacuuming, sealing, and dehumidifying, a licensed pest control company can assess whether there’s a moisture or structural issue you’ve missed.
Cellar Spiders Are Harmless
Before you go to war, it’s worth knowing what you’re dealing with. Cellar spiders pose zero health risk. There’s a persistent myth that they have the most potent venom of any spider but can’t bite humans because their fangs are too short. Neither part is true. Their fangs are short, but their venom is also weak, and they rely almost entirely on their webs to subdue prey rather than biting. They don’t damage your home, don’t contaminate food, and actually reduce populations of other insects and spiders.
If your only issue is a few cellar spiders in a far corner of the basement, leaving them alone is a perfectly reasonable option. But if the webs are spreading across your ceiling, multiplying in every room, or you simply don’t want them around, the combination of vacuuming, moisture control, food source elimination, and sealing will clear them out and keep them out.