Spiders in Your Montreal Basement? What They Are and What to Do
Basements and spiders go together in Montreal like winter and potholes. If you have a basement — especially in an older building — you have spiders. The question is whether they are a problem or just unwelcome roommates.
The short answer: most of them are harmless, and some are actually helpful. But there are situations where spider populations indicate a bigger issue.
Common Basement Spiders in Montreal
House Spider (Parasteatoda tepidariorum)
Small, brownish, builds messy cobwebs in corners and along floor joists. This is the most common spider in Montreal basements. Completely harmless. They eat other insects — including ants, flies, and mosquitoes.Long-Bodied Cellar Spider (Pholcus phalangioides)
The classic "daddy longlegs" spider (though technically not a daddy longlegs — that is a different arachnid). Very thin legs, small body, builds loose webs in ceiling corners. Harmless and actually predatory toward other spiders, including more problematic species.Wolf Spider (Pardosa and Trochosa species)
Larger — up to 25mm body length. Brown with darker markings. Does not build webs. Hunts on the ground, often seen running across basement floors. They look intimidating but are not aggressive and their bite, while possible, is comparable to a bee sting.Sac Spider (Cheiracanthium mildei)
Pale yellow-green, about 10mm. Builds small silk sacs in upper corners and along ceiling-wall junctions. This is the one Montreal spider that occasionally bites humans. The bite causes localized pain, redness, and mild swelling — similar to a mosquito bite but more persistent. Not medically significant for most people.Brown Recluse — NOT in Montreal
Despite what the internet suggests, brown recluse spiders do not live in Quebec. Their range does not extend this far north. If someone tells you they found a brown recluse in their Montreal basement, they are almost certainly misidentifying a different species. This is a common and persistent myth.When Spiders Are Actually a Problem
A few spiders in the basement is normal and even beneficial. But an unusual concentration of spiders often indicates a food source problem — meaning you have a larger insect population that the spiders are feeding on.
Call an exterminator if:
- You are seeing dozens of spiders regularly — this suggests a significant insect population in the basement
- You are finding spider webs reforming within days of cleaning them
- You are seeing insects that the spiders are feeding on — centipedes, silverfish, earwigs, ants, or drain flies in large numbers
- Anyone in the household has a severe fear (arachnophobia) that is affecting their quality of life — this is a legitimate reason to seek professional treatment
Reducing Spiders in Your Basement
Reduce Moisture
Spiders and their prey thrive in damp environments. Use a dehumidifier to keep basement humidity below 60%. Fix any water infiltration, leaking pipes, or condensation issues.Reduce Clutter
Spiders hide in undisturbed areas — cardboard boxes, stacked furniture, stored clothes. Replace cardboard with plastic storage bins. Keep items off the floor. Reduce the number of hiding spots.Seal Entry Points
Spiders enter through gaps around pipes, windows, foundation cracks, and where utilities enter the building. Caulk and weatherstrip these areas. Install door sweeps on basement doors.Regular Cleaning
Vacuum webs, egg sacs, and spiders regularly. This is more effective than spraying. Focus on corners, along floor joists, window wells, and around the water heater and furnace.Reduce Outdoor Habitat
Spider populations start outside and move in. Keep vegetation trimmed away from the foundation. Remove leaf litter, woodpiles, and debris from along the house. Replace exterior white light bulbs with yellow or sodium vapor lights — they attract fewer insects, which means fewer spiders follow.Professional Spider Treatment
If spider populations are high enough to warrant professional treatment, an exterminator will typically:
1. Inspect the basement to identify species and locate concentrations 2. Treat the perimeter — interior and exterior — with a residual insecticide 3. Apply dust formulations in wall voids, behind baseboards, and in crawl spaces 4. Address the underlying insect population that is sustaining the spiders 5. Recommend environmental modifications (moisture control, sealing, lighting)
Cost for a residential spider treatment in Montreal: $150-$300, usually including one follow-up visit.
Frequently Asked Questions
Are any spiders in Montreal dangerous?
No spider species in the greater Montreal area is considered medically dangerous. The sac spider can deliver a mildly painful bite, but it is not dangerous to healthy adults. Brown recluse and black widow spiders are not established in Quebec.Why do I have more spiders in fall?
Male spiders become more active in late summer and fall as they search for mates. This increased movement makes them more visible. Additionally, cooling temperatures drive both spiders and their insect prey indoors, concentrating populations in basements.Got a pest problem?
Extermination DMP serves Montreal, the South Shore, Laval & the West Island — 24/7.
Call 438-879-5706