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How to identify it
- Oval, rounded above and flat below, with seven overlapping plates and seven pairs of legs; adult insects have three pairs.[1][5][3]
- Gray to brown. Kentucky says they rarely exceed 3/4 inch; UC IPM gives adults as about 1/3 to 3/4 inch and Clemson as 1/4 to 5/8 inch.[1][5][3]
- Pillbugs roll into a tight ball when disturbed. Sowbugs can't; they are flatter on top, scurry away instead, and have two tail-like appendages (uropods) at the rear.[1][5][3]
- Young are pale yellow to whitish and about 1/12 inch long when they leave the mother's brood pouch; recently molted individuals can look bluish or purplish.[5]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Millipedes | Long and wormlike, with two pairs of legs on most body segments and many more legs overall than the seven pairs of a sowbug or pillbug.[2][5] |
Where it lives
Live in damp leaf litter, mulch and under stones and pots outdoors, and wander into crawl spaces, basements and ground floors looking for moisture.[1]
Biology and life cycle
They breathe with gill-like structures and must stay moist, so they hide by day under mulch, leaf litter, rocks, boards and logs and come out at night to feed.[3][1]
Kentucky says a pillbug rolls into a ball not only for defense but also to hold in water.[1]
Females carry eggs and young in a brood pouch on the underside. UC IPM says eggs hatch about a month after they are produced and the young stay in the pouch about 2 weeks; Kentucky says there are 1 to 2 broods a year of about two dozen young, which take 2 to 3 months to mature.[5][1]
Young molt about every 1 to 2 weeks as they grow. Kentucky gives a life span of about 3 years; UC IPM says adults can live 2 to 5 years.[5][1]
They eat fungi and decaying plant matter, and Clemson says some species occasionally feed on carrion. In the garden they help recycle dead plant material and return nutrients to the soil.[1][3][5]
Damage and signs
- In gardens they occasionally chew seedlings, new roots, lower leaves and fruits or vegetables touching damp soil.[5][1][3]
- They can't damage household furnishings; indoors they are only a nuisance.[4]
- Clemson says indoor invasions usually follow a long, wet spring, and many indoors usually means a large population outside.[3]
Health risk
Sowbugs and pillbugs don't bite or sting and are harmless to people and pets.[1][3][4]
Control
Prevention
Remove leaves, mulch, lumber, rotting wood, stones and flowerpots from beside the foundation and entrances, and improve drainage so the soil there stays drier.[1][3]
Keep plants, mulch and other debris at least several inches back from the foundation and farther from doorways, keep irrigation water off the foundation, and raise planters and pots so air moves underneath. Check that thick door mats aren't sheltering them.[5][3]
In gardens, water early in the day so surfaces are dry by evening, keep compost and mulch back from plants, and consider raised beds, drip irrigation or plastic mulch; UC IPM says black plastic may work better than white or clear.[5]
Keep them out
Make sure doors and windows fit tightly, and seal foundation cracks and gaps where they get in.[3][4][1]
Sanitation
Indoors, dry out damp hiding places: fix water problems and improve ventilation in basements and crawl spaces.[3][4]
Traps and physical control
Sweep, vacuum or pick them up and carry them outside.[1][4]
Pesticides
Indoor insecticides are usually of little use because they die from lack of moisture. If a perimeter insecticide is used outdoors, rake away leaf litter and use enough water to carry it down to the soil, and expect problems to return unless the moisture is fixed.[1][4]
What roly-polies indoors are telling you
Without high moisture they can hardly survive indoors, so repeated finds point to damp spots in or around the house and to a way in.[1][4]
Look first at ground-level doors, basements, crawl spaces and ground floors, the places they reach while searching for water.[1][3]
Occasional strays can simply be tolerated and removed; persistent problems mean finding and drying out the source outdoors.[4][3]
Where sources disagree
Size: Kentucky says rarely more than 3/4 inch; UC IPM gives about 1/3 to 3/4 inch and Clemson 1/4 to 5/8 inch.[1][5][3]
Life span: Kentucky says about 3 years; UC IPM says adults can live 2 to 5 years.[1][5]
Breeding indoors: Kentucky says they find it almost impossible to survive indoors without high moisture; Iowa State says dark, damp areas of a house may become breeding sites, though most found indoors come from outside.[1][4]
Indoor insecticide: Kentucky says indoor applications are typically of little use; Iowa State says a light residual treatment of cracks and corners may be of some benefit.[1][4]
Need for control: Clemson says they rarely, if ever, require management; Iowa State says persistent problems require locating and eliminating or treating the source areas.[3][4]
Common questions
- Why do I find roly-polies in my basement?
- They need moisture and come in looking for it; dampness or gaps around doors are the cause to fix.[1][3]
- Are roly-polies insects?
- No. They are crustaceans (isopods), related to shrimp and crayfish, and adults have seven pairs of legs instead of an insect's three.[4][5][3]
- Do pillbugs and sowbugs hurt garden plants?
- Mostly they eat decaying matter, but they occasionally chew seedlings, new roots and fruits or vegetables lying on damp soil. Drier soil surfaces and less organic litter around plants help.[5][1]
- How do I tell a sowbug from a pillbug?
- Touch it: a pillbug rolls into a ball, while a sowbug can't, runs off, and has two small tail-like points at the rear.[1][5][3]
Sources
- University of Kentucky Entomology, “ENTFACT-439: Sowbugs and Pillbugs.” entomology.mgcafe.uky.edu/ef439 (accessed 2026-11-11)
- Penn State Extension, “Millipedes.” extension.psu.edu/millipedes (accessed 2026-11-11)
- Clemson Cooperative Extension, Home & Garden Information Center, “Sowbugs & Pillbugs (HGIC).” hgic.clemson.edu/factsheet/sowbugs-pillbugs/ (accessed 2026-11-11)
- Iowa State University Extension and Outreach, “Sowbugs and Pillbugs (Yard and Garden).” hortnews.extension.iastate.edu/sowbugs-and-pillbugs (accessed 2026-11-11)
- University of California Statewide IPM Program, “Pillbugs and Sowbugs.” ipm.ucanr.edu/PMG/GARDEN/FRUIT/PESTS/sowbugs.html (accessed 2026-11-11)
- iNaturalist, “Armadillidium vulgare taxon page (order and family).” www.inaturalist.org/taxa/56083 (accessed 2026-11-11)