These moisture-dependent crustaceans usually live outdoors and sometimes wander inside. Simple removal and checking nearby damp shelter are more appropriate than assuming structural damage.
Pillbugs and sowbugs are moisture-dependent land crustaceans that sometimes wander into homes. Pillbugs can roll into a ball; sowbugs have visible tail-like projections and cannot roll tightly. A few indoor sightings usually call for simple removal and a check of nearby damp shelter, not a whole-yard treatment.
What Are Pillbugs and Sowbugs?
Pillbugs and sowbugs are not insects. They are crustaceans that belong to a group of animals called isopods. They are terrestrial crustaceans, although they still depend on moist conditions.
Both animals are common throughout the South. They are wingless and oval or slightly elongated. Most adults reach about 1/2 inch long.
They are usually slate-gray. Their body segments look like small overlapping plates of armor. Because of that, many people mistake them for tiny beetles at first glance.
Key Identification Features
When you get a close look, check for these traits:
- Size: roughly 1/2 inch (13 mm) as adults
- Color: slate-gray
- Shape: oval or slightly elongated, with armor-like body segments
- Legs: seven pairs, compared with the three pairs an insect has
- Wings: none
- Movement: slow, steady crawling rather than quick darting
The leg count is a helpful clue. If you see a small gray critter with fourteen legs, you’re most likely looking at an isopod.
How to Tell a Rolling Pillbug From a Tailed Sowbug
Pillbugs and sowbugs look alike, and their habits are nearly the same. Still, two features make them easy to separate once you know what to look for.
The Roll Test
Pillbugs are the famous “roly-polies.” When disturbed, they roll into a tight ball. That habit is where the nickname comes from.
Sowbugs can’t do this. If you touch a sowbug, it will try to crawl away instead. It can’t form a tight ball.
The Tail Check
Look at the back end of the animal. Sowbugs have two small, tail-like appendages at the rear. Pillbugs don’t have these appendages, so their back end looks smooth and rounded.
Sowbugs are often called woodlice. They also have well-developed eyes, but you’ll need a close look to notice that detail.
Here’s a quick side-by-side summary:
- Pillbug: rolls into a tight ball, no tail-like appendages
- Sowbug: cannot roll into a ball, two tail-like appendages at the rear
What Do These Isopods Eat?
Both animals feed mainly on decaying organic matter. Rotting leaves, old mulch, grass clippings, and decaying vegetation all serve as food. In this way, they help break down plant debris in the yard.
However, it’s not accurate to call them harmless to every plant. University of Florida researchers note that they occasionally damage the roots of green plants. Gardeners tend to watch young plants growing in damp, mulch-heavy beds most closely.
In most yards, this feeding is occasional and minor. Still, if you’re starting tender plants in moist soil, keep an eye on the roots near the soil line.
Where Do They Live Outdoors?
These isopods need high moisture to survive. That’s why they stay in damp, sheltered spots during the day. They come out to move and feed mostly at night.
During the day, you’ll usually find them resting in places like these:
- Under rocks and stepping stones
- Beneath boards and other wood lying on the ground
- Inside leaf litter or piles of decaying vegetation
- Under trash and garden debris
- Just below the soil surface
Mulch, grass clippings, and leaf litter give them both food and shelter. Because they’re active at night, you often discover them in the morning. Doorways, patios, and garage entries are common places to spot them.
Why Do They Wander Indoors?
Pillbugs and sowbugs are outdoor animals. When they show up inside, they’ve wandered in by chance. They aren’t infesting the structure. UF/IFAS says they occasionally wander indoors but do not cause damage.
Several conditions near the house make wandering more likely:
- Thick, damp mulch right against the foundation
- Leaf litter and decaying vegetation piled near walls
- Boards, debris, and clutter that hold moisture beside the house
- Gaps under doors and openings along the foundation
- Potted plants brought indoors from a patio or porch
According to the UF/IFAS fact sheet, a heavy indoor population usually means there’s a large population outdoors. In other words, the indoor sightings start with conditions in the landscape around the home. Looking outside first is the best way to understand what you’re seeing.
How They Differ From Centipedes and Millipedes
Homeowners often lump pillbugs together with other many-legged critters found in damp areas. However, centipedes and millipedes belong to different groups of arthropods. Telling them apart helps you understand what you’re dealing with.
After you rule out an isopod, the next step is usually figuring out whether you have a centipede or a millipede. Centipedes are flattened, fast runners with one pair of legs on most body segments. Millipedes are wormlike and cylindrical, with two pairs of legs on most segments. Millipedes eat decaying plant matter and coil up when disturbed. Centipedes, however, hunt insects and spiders. Our centipede and millipede comparison compares both animals side by side and explains household prevention steps that keep them outside.
Centipedes deserve a closer look because their habits differ the most from isopods. They are active predators, and the larger species can inflict painful bites. Indoors, they tend to turn up in closets and bathrooms where humidity is high. If you keep finding centipedes instead of roly-polies, our article on why centipedes show up in your house explains the causes and solutions in more detail.
Here’s a quick way to separate all three:
- Pillbug or sowbug: short, oval, armored, seven pairs of legs, slow
- Millipede: long, round, wormlike, two pairs of legs per segment, coils up
- Centipede: long, flat, one pair of legs per segment, very fast, predatory
The Isopod Life Cycle
Their life cycle explains why populations can build up in moist yards. In Florida, breeding can happen year-round.
The female carries her eggs in a brood pouch, called a marsupium, on the underside of her body. Each brood holds anywhere from seven to 200 eggs. The eggs hatch in three to seven weeks.
The young develop in the protective pouch before leaving it. Development and brood timing vary with conditions.
Usually, one or two broods occur each year, depending on conditions. Individuals may live to be two years old. As a result, a damp, sheltered flower bed can support a steady population season after season.
Are They Harmful Inside Your Home?
According to UF/IFAS, sowbugs and pillbugs cause no damage inside the home. Unlike termites, they don’t attack the structure of your house.
Mostly, they’re just annoying. Finding them on your floor can be unsettling, especially in larger numbers. However, they’re a useful sign of moisture and organic debris close to your foundation.
Outdoors, the picture is slightly different. Large populations in garden beds may occasionally damage the roots of green plants. For most homeowners, though, the indoor nuisance is the bigger concern.
Simple Ways to Handle Indoor Strays
These animals cause no damage indoors, and removing a few strays is easy. A broom and dustpan work well. A vacuum is another simple option.
If they become a serious nuisance, focus on what draws them close. Removing hiding places, food material, and moisture sources will cut their numbers. In addition, check potted plants for activity before bringing them inside.
Isopods and many other occasional invaders have one thing in common: they need moisture. Damp soil, wet mulch, and debris along the foundation all create the conditions they need. Our guide to moisture control for pest prevention explains how managing water around your home helps keep pests and related damage out over time.
UF/IFAS also recommends a few outdoor habits:
- Avoid deep, persistently wet mulch against the foundation; depth alone does not determine whether it dries
- Remove compost piles and decaying vegetation from areas close to the house
- Clear boards, trash, and debris where they hide during the day
The same fact sheet notes that insecticides are sometimes used when nuisance pressure is heavy. However, those treatments should generally come after breeding sites and hiding spots are removed. If you go that route, follow the product label exactly.
Source Used for This Guide
The identification, biology, and control details in this article come from University of Florida extension research. You can read the original fact sheet from UF/IFAS Extension on pillbugs, sowbugs, centipedes, millipedes, and earwigs.
Frequently Asked Questions
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Are pillbugs insects?
No. Pillbugs are terrestrial crustaceans in the isopod group. Unlike insects, they have seven pairs of legs. They also need high moisture to survive.
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What is the difference between a roly-poly and a sowbug?
A roly-poly, or pillbug, can roll into a tight ball and has no tail-like appendages. A sowbug cannot roll into a ball. It also has two small tail-like appendages at its rear.
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Do pillbugs damage gardens?
They feed mainly on decaying organic matter like leaf litter and mulch. However, they occasionally damage the roots of green plants. That feeding is most likely in damp, heavily mulched beds.
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When are pillbugs most active?
Pillbugs are most active at night. During the day, they rest under trash, rocks, boards, decaying vegetation, or just beneath the soil surface. In Florida, they can breed year-round.
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How long do pillbugs live?
Individuals may live to be two years old. Females usually produce one or two broods each year. Each brood can contain from seven to 200 eggs.
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How do I get pillbugs out of my house?
A broom and dustpan or a vacuum is usually all you need indoors. If they keep showing up, cut back on moisture, mulch depth, and debris near the foundation. Those outdoor conditions are what keep the population going.
Vincent founded On Demand Pest Control in 2017 and is a Florida Certified Operator in all four state categories. He treats pest control as a systematic problem to solve, not a symptom to spray. Read Vincent’s full bio →
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