Roly-poly bugs, also called pillbugs, enter homes almost exclusively because of excess moisture, so the single most effective way to get rid of them is to dry out the spaces where they’re congregating. Unlike many household pests, roly-polies don’t breed indoors, don’t eat your food, and don’t bite. They wander in from outside through gaps and cracks, and once indoors they usually die within a couple of days unless they find damp conditions. That biology works in your favor: fix the moisture, seal the gaps, and the problem resolves itself without much need for pesticides.
Why Roly-Polies Are in Your Home in the First Place
Roly-polies aren’t insects at all. They’re terrestrial crustaceans, more closely related to shrimp and crabs than to ants or cockroaches. That lineage explains their one non-negotiable requirement: moisture. They breathe through gill-like structures on the underside of their bodies, and those gills need to stay damp to function. A dry room is essentially suffocating for them. When you find a cluster of roly-polies in your basement, bathroom, or laundry room, they didn’t choose your house because it had something tasty. They followed a moisture gradient through whatever opening was available.
Outdoors, pillbugs thrive under mulch, leaf litter, rotting wood, stones, and compost piles, all places where decaying organic matter holds moisture. They feed primarily on decomposing plant material, which makes them genuinely useful in garden ecosystems as recyclers of dead vegetation.1EDIS / University of Florida. Pillbugs, Centipedes, Millipedes and Earwigs: ENY-221/IG093 The trouble starts when outdoor habitat butts right up against your foundation wall. Mulch beds against the house, stacked firewood near a door, dense ground cover creeping up to the siding: these create highways from their outdoor world into yours.
Dry Out the Indoor Spaces They’re Using
Because roly-polies depend on humidity to survive, moisture control is the most reliable elimination method. Start with the specific room where you’re finding them and work outward.
- Dehumidifiers: In basements and crawl spaces, running a dehumidifier and keeping relative humidity below 60% makes the environment hostile to pillbugs within days.
- Ventilation: Bathrooms and laundry rooms need exhaust fans that actually vent to the outdoors, not just into an attic. If your bathroom fan is weak or broken, replacing it is one of the highest-impact fixes.
- Leaks: Check under sinks, around toilets, near water heaters, and along basement walls for any slow drip or seepage. Even a small, persistent leak creates exactly the microhabitat roly-polies need.
- Standing water: Plant saucers, pet water bowls left on the floor overnight, and condensation trays under refrigerators all contribute to localized humidity at floor level, right where pillbugs crawl.
Fixing moisture issues solves the problem at its root. You’ll often notice the bugs disappearing within a week of getting a damp area dried out, because the ones already inside simply die without adequate humidity, and new ones stop coming in once the moisture signal fades.
Seal the Entry Points
Roly-polies are small enough to squeeze through surprisingly tight gaps, but they aren’t great climbers on smooth surfaces and they don’t chew through materials. That means physical exclusion works well if you know where to look. The most common entry points are at ground level or below.
Start with the junction between your foundation and the sill plate, the bottom edge of the house where the wooden framing meets the concrete or block foundation. Gaps here are extremely common in older homes. Exterior-grade caulk or expanding foam seals these effectively. Check around basement windows, dryer vents, water spigots, and any pipe or wire penetration through the foundation wall. Door sweeps on exterior doors, especially garage doors and basement entries, close another major pathway.
Sliding glass doors deserve special attention. The tracks often have small gaps at the corners that are easy for pillbugs to navigate, and the tracks themselves can collect moisture from condensation. Cleaning the tracks and adding weatherstripping helps on both fronts.
If you have a crawl space with a dirt floor, that’s likely a significant source. Encapsulating the crawl space with a vapor barrier over the soil surface reduces both moisture and easy access for ground-dwelling creatures. Full crawl space encapsulation is a bigger project, but it pays dividends for roly-polies, moisture damage, and energy efficiency all at once.
Modify the Outdoor Habitat Near Your Foundation
You’ll never eliminate every roly-poly in your yard, nor would you want to. They’re beneficial decomposers. But you can make the zone right next to your house much less inviting, which dramatically reduces the number that wander inside.
Pull mulch back so there’s a gap of at least six inches between any organic mulch and your foundation. Better yet, use a strip of gravel or crushed stone against the house instead of wood mulch. Gravel drains fast and doesn’t hold the moisture that pillbugs need. Move firewood stacks, compost bins, and piles of leaves or yard debris well away from exterior walls. Trim ground-cover plants and dense shrubs that press against the foundation, because these trap moisture at the soil surface right where it does the most harm.
Drainage matters outdoors too. If rainwater pools against your foundation, that saturated soil becomes prime roly-poly territory. Make sure gutters are clear, downspouts direct water at least three to four feet away from the house, and the grade slopes away from the foundation rather than toward it. These fixes address the moisture that attracts pillbugs long before they ever reach a crack in the wall.
When Chemical Treatments Make Sense
For most roly-poly intrusions, the moisture and exclusion steps described above are sufficient. But if you’re dealing with large numbers coming in regularly, especially in spring or fall when outdoor populations peak, a targeted pesticide application can help as a supplement. The emphasis is on supplement: spraying without fixing moisture and entry points is like mopping while the faucet is still running.
Outdoor perimeter treatments are more effective than indoor sprays for pillbugs. Applying a residual insecticide labeled for crawling pests along the foundation exterior, focusing on the base of walls, around door frames, and near known entry points, creates a barrier that kills pillbugs before they get inside. Granular baits containing carbaryl or other labeled active ingredients can be spread in mulch beds and garden borders where populations are densest. University of Florida extension guidance emphasizes that combining good hygiene and waste management with targeted insecticide use is the most effective strategy for pillbugs and similar ground-dwelling pests.1EDIS / University of Florida. Pillbugs, Centipedes, Millipedes and Earwigs: ENY-221/IG093
Indoors, spraying is rarely necessary. If you find a handful of roly-polies in a basement corner, vacuuming them up is faster and more practical than applying chemicals in living spaces. Diatomaceous earth, the food-grade variety, can be dusted into cracks along baseboards and around pipe penetrations as a low-toxicity option. It works by damaging the waxy coating on their bodies, causing them to lose moisture and die. It’s slow-acting but effective in dry areas. Note that diatomaceous earth stops working when it gets wet, so it’s useless in the damp environments where pillbugs actually thrive. It functions best as a barrier in transitional zones, the dry side of a gap they’d have to cross to reach the humid spot they’re targeting.
Are Roly-Polies Actually a Problem?
Here’s where the advice gets a bit unconventional for a pest-removal article: roly-polies are among the most harmless creatures that can show up in a home. They don’t sting, bite, or transmit disease. They don’t damage wood, fabric, or stored food. They don’t reproduce indoors under normal household conditions because the environment simply isn’t wet enough for their offspring to survive. Unlike termites, carpenter ants, or cockroaches, pillbugs inside your home are a nuisance, not a structural or health threat.
What they are, though, is a reliable indicator of a moisture problem. If you’re regularly finding roly-polies indoors, your home has excess moisture somewhere, and that moisture could eventually cause mold, wood rot, or conditions that attract pests that are genuinely damaging. In that sense, pillbugs are doing you a favor by flagging a problem you’d want to fix anyway.
In gardens, the story is slightly different. While pillbugs primarily eat decaying matter, they can occasionally damage seedlings, strawberries, and other tender plants at ground level, especially when populations are large and decomposing material is scarce. But indoors, they’re just lost crustaceans slowly drying out.
The Conglobation Response and What It Tells You
The “roly-poly” name comes from their signature defense: when disturbed, they curl into a tight ball, a behavior scientists call conglobation. This is specific to pillbugs (Armadillidium vulgare) and distinguishes them from sowbugs, which look similar but are flatter and can’t roll up. If the bugs you’re finding curl into a ball when you poke them, they’re pillbugs. If they scurry away flat, they’re sowbugs. Both are isopods, both need moisture, and both respond to the same control methods, but the distinction matters if you’re reading pesticide labels or extension service guides that differentiate between the two.
Research on conglobation has revealed that it’s not just a predator defense. Pillbugs also roll into balls more frequently in response to temperature stress. In laboratory settings, Armadillidium vulgare showed significantly higher rates of conglobation at both cold and warm temperature extremes compared to moderate conditions, suggesting the behavior also helps regulate body temperature and reduce moisture loss.2The Classic. Conglobation of Armadillidium vulgare as a Behavioral Adaptation for Thermoregulation This is a small detail, but it matters practically: if you find curled-up pillbugs in a spot that seems dry, the curling itself may be their attempt to conserve moisture in a hostile environment. They’re already dying. You don’t need to treat that area; you just need to figure out how they got there and close the path.
Pillbugs vs. Sowbugs vs. Other Look-Alikes
People sometimes confuse roly-polies with other small, dark, ground-dwelling creatures. Sowbugs are the closest relatives and share the same habitats, but as mentioned, they can’t roll into a ball and they have two small tail-like appendages at the rear that pillbugs lack. Control methods are identical for both.
Millipedes sometimes get lumped in with roly-polies because they’re also moisture-loving, slow-moving, and curl up when threatened. But millipedes are much longer, have many more legs, and some species can release a mildly irritating fluid when handled. They respond to the same moisture-reduction strategy, so if you’re seeing a mix of pillbugs and millipedes, the underlying fix is the same.
Carpet beetle larvae, on the other hand, are a genuinely different problem that occasionally gets confused with small isopods at a glance. Carpet beetle larvae are fuzzy, somewhat oval, and actively eat natural fibers like wool, silk, and feathers. If your “roly-poly” problem involves tiny bugs near closets and upholstered furniture rather than basements and bathrooms, take a closer look. The treatment for carpet beetles involves cleaning, vacuuming fabrics, and sometimes insecticide, which is a completely different approach from the moisture-focused strategy that handles pillbugs.
Seasonal Patterns and When to Expect Them
Roly-poly invasions tend to follow a seasonal rhythm. Spring is a common peak because rising temperatures activate outdoor populations at the same time that spring rains saturate soil near foundations. Fall brings a second wave as temperatures drop and pillbugs seek warmer, moister refuges. Summer can bring them indoors if irrigation keeps foundation soil damp, and heavy rainstorms at any time of year can flush them toward buildings.
Understanding the seasonal pattern helps with timing your prevention efforts. The best time to apply a perimeter treatment or seal foundation gaps is in early spring, before the first major wave. If you know you have a recurring problem, doing your mulch-and-drainage maintenance in late winter gives you a head start. You’ll likely never get to zero pillbugs finding their way inside, especially in older homes, but reducing the number from dozens to a rare straggler is entirely achievable with consistent moisture management and good exclusion.
Handling a Sudden Large Invasion
Occasionally, people report finding hundreds of roly-polies in a short period, often after a heavy rain, a flooding event, or when a previously unknown leak suddenly worsens. This can be alarming, but it doesn’t mean you have an infestation in the traditional sense. Pillbugs aren’t nesting in your walls or multiplying in your basement. A mass appearance usually means a large outdoor population got displaced by water and funneled through a gap you didn’t know existed.
The immediate response is simple: vacuum them up. A shop vac works well for large numbers. Then investigate the moisture source. Check the foundation wall in the area where they appeared for new cracks, failed caulk, or water stains. Look outside at the corresponding spot for pooling water, clogged gutters, or soil that has settled and now directs runoff toward the house. A sudden influx of pillbugs is usually a clue that something changed in the drainage or moisture pattern around that part of your home.
If the invasion happened during a major storm and the moisture source is obvious and temporary, the problem often resolves on its own once things dry out. Seal whatever gap they used, clear any debris outside, and keep an eye on the area during the next rain. If the invasion is recurring or the moisture source isn’t obvious, it may be worth having a pest control professional inspect the exterior, not so much for the pillbugs themselves, but to identify the moisture pathway that’s drawing them in.