Reviewed by William "Willy" Vizcarrondo, NYS DEC Certified Commercial Pesticide Applicator C1825832. Updated September 23, 2026.
Quick answer
Bugs end up in your basement for two reasons: moisture and gaps. Nearly every insect Long Island homeowners find downstairs is an outdoor pest that survives on damp soil and leaf litter, then walks in through a foundation crack, a utility penetration, a bad door sweep, or a window well. Basements sit below grade against wet soil, which makes them the most humid room in the house, so the bugs that get in stay alive. They are not a sign of a dirty home. They are a sign that the outside of your house is easier to enter than it should be, and that the air inside is holding too much water.
House centipede. Long legs, fast, alarming. Penn State says adults have 15 pairs of legs and feed on silverfish, firebrats, carpet beetle larvae, cockroaches, spiders, and other small arthropods. A centipede means there is something for it to eat.
Camel cricket. Humpbacked, wingless, and it jumps at you. NC State notes they have no wings as adults and do not chirp. Rutgers says they feed on starch, fungi, and occasionally fabrics, and that the glue in cardboard boxes can serve as food. Missouri Extension says they invade buildings in fall seeking places to pass the winter.
Silverfish. Teardrop shaped, silver, wriggling. UC IPM says silverfish live and develop in damp, warm places, need relative humidity above 75 percent, eat paper with glue or paste and book bindings, and can live about 3 years.
Springtail. Tiny jumping specks near the sump or floor drain. UC IPM puts them at about one sixteenth of an inch, says they are sometimes confused with fleas, and notes they soon die after entering a home unless they find moisture.
Sowbug and pillbug. Gray, armored, slow. NC State explains they are land crustaceans that breathe through gills and congregate in moist situations. Maryland Extension notes that pillbugs can roll into a ball but sowbugs cannot, and that both typically dry out quickly and die indoors.
Earwig. Pincers on the back end. Ohio State says earwigs are harmless to people and do not seek to hide inside your ears; by day they hide in dark, moist, cool places like mulch, and at night they become active and wander.
Cellar spider. Long legged, in the corners. Clemson describes cellar spiders constructing loose haphazard webs, often in corners, to catch insect prey.
No. Oklahoma State's fact sheet says centipedes have venom glands, but a bite usually produces a moderate reaction that at worst is similar to a bee sting, and that they carry no disease to humans, animals, or plants. They are also the one basement bug that is working for you, since Penn State lists silverfish and cockroaches on their menu. A basement with centipedes is a basement with prey, and the prey is the actual problem.
Too much water and too many openings. Cornell's IPM program cites the EPA recommendation that indoor moisture levels not exceed 60 percent and ideally fall between 30 and 50 percent, and recommends a dehumidifier to bring a basement under 60 percent. University of Minnesota's basement moisture guide says downspout extensions should discharge at least 4 feet beyond the wall and that grade should slope away from the foundation at least 1 inch per foot for 6 feet. If your downspout dumps at the foundation and your basement smells damp, the bugs are just reporting the conditions.
Because the bugs are coming from outside and dying inside. The Illinois Department of Public Health calls these occasional invaders and notes they often die indoors because moisture and food sources are insufficient. Its guidance on treatment is the one we follow: the most effective and least hazardous applications are outdoor applications, residual products applied in a band to the ground immediately around the foundation. Spraying the basement floor kills what is there today and does nothing about tomorrow's arrivals.
We walk the outside first. Grade, downspouts, mulch against siding, gaps at pipes and cables, window wells, and door sweeps. Then a perimeter band treatment around the foundation, the way Illinois DPH describes, and a crack and crevice treatment at interior entry points where needed. You get a short written list of the moisture and entry fixes specific to your house.
General insect treatment carries no guarantee, because the yard and the humidity are yours, and we say that up front. Quotes are free and in writing.
Dry it out and close it up. Run a dehumidifier to get under 60 percent humidity. Extend downspouts at least 4 feet from the wall and regrade where soil slopes toward the house. Cornell's advice is to avoid mulch in direct contact with the home. Clemson's checklist covers the rest: move the woodpile away from the house, trim branches and shrubbery so they are not touching the structure, keep gutters free of leaves, and seal cracks and crevices in the foundation with silicone caulk. Get the cardboard off the basement floor and into plastic bins; Rutgers notes the glue is cricket food. Fix the door sweep. Screen the window wells.
On Long Island, usually house centipedes, camel crickets, silverfish, springtails, sowbugs and pillbugs, earwigs, and cellar spiders. Jumping specks near the sump are springtails; slow armored crawlers are sowbugs or pillbugs.
No. They mean humidity, water at the foundation, and gaps. Illinois DPH describes these as occasional invaders that wander in from outside and often die indoors.
No. Oklahoma State says a bite at worst is similar to a bee sting and that they carry no disease. They eat the other basement bugs.
Missouri Extension says camel crickets invade buildings in fall seeking places to pass the winter, and the other occasional invaders follow the same pattern as the soil cools.
It helps a lot. Cornell recommends bringing indoor humidity under 60 percent, and UC IPM says silverfish need humidity above 75 percent and springtails die without moisture. It will not stop entry, so seal the gaps too.
A perimeter band treatment, which Illinois DPH describes as the most effective application, cuts what gets in for the season. There is no guarantee on general insect treatment because moisture and entry are the real drivers.
Related reading
Sources: Penn State Extension, House Centipedes; Oklahoma State Extension, Centipedes and Millipedes; NC State Extension, Camel Crickets; Rutgers NJAES, Cave Crickets; University of Missouri Extension, House-Invading Crickets; UC IPM, Silverfish and Firebrats; UC IPM, Springtails; NC State Extension, Pillbugs and Sowbugs; University of Maryland Extension, Pillbugs and Sowbugs; Ohio State University Extension, Earwigs; Clemson HGIC, Cellar Spiders; Clemson HGIC, Checklists to Prevent Insects in Your Home; Cornell NYS IPM, Moisture Pests; Illinois Department of Public Health, Occasional Invaders; University of Minnesota Extension, Moisture in Basements.
Still not sure? Call (516) 509-6001 and we'll tell you what you're dealing with.
This article is general pest information for Long Island homeowners, not a diagnosis of your specific situation. Pest behavior varies by home, season, and species, and every job is quoted in writing before any work begins. Pesticide applications are performed by licensed New York State applicators in accordance with label requirements.