Pill Bugs and Sow Bugs | Pest ID Guide
Quick Facts About Pill Bugs and Sow Bugs
Pill bugs and sow bugs, also called roly-polies and woodlice, aren’t insects at all. They’re land-dwelling crustaceans, related to shrimp and crabs, that need moisture to survive. Finding them indoors almost always points to a damp area.- Size: About 1/4 to 5/8 inch
- Color: Slate gray to brownish-gray
- Body: Oval and segmented, like armor plates, with seven pairs of legs
- Diet: Decaying leaves, mulch, and wood; occasionally tender seedlings
- Where found: Under mulch, stones, boards, leaf litter, and flowerpots
- Indoors: Usually die within a day or two unless they find moisture
Pill Bugs vs. Sow Bugs
- Rolling up: Pill bugs roll into a tight ball when disturbed. Sow bugs can’t.
- Tail: Sow bugs have two small tail-like appendages at the rear; pill bugs don’t.
- Shape: Pill bugs are more rounded; sow bugs are flatter.
Both behave the same way and are managed the same way.
Why They Come Inside
Pill bugs and sow bugs breathe through gill-like structures that must stay moist. When their outdoor habitat gets too wet after heavy rain, or too dry during a drought, they wander, and many find their way in under doors and through gaps along the foundation. Thick mulch and leaf litter against the house put large populations right at your door.
Signs and Where They Gather
- Basements and crawl spaces: Especially damp ones
- Garages and ground-floor rooms: Near doors and along baseboards
- Around foundations: Under mulch, stones, and landscape timbers
- Patios and walls after rain: On damp masonry and walkways
Are They Harmful?
No. Pill bugs and sow bugs don’t bite, sting, carry disease, or damage homes. Outdoors they help break down dead plant material, though large numbers can nibble seedlings. Indoors, they’re a nuisance and a signal that moisture needs attention.
How to Keep Them Out
- Reduce mulch and leaf litter: Keep a strip of bare ground or gravel along the foundation.
- Fix drainage: Clean gutters, extend downspouts, and correct low spots near the house.
- Dry out damp spaces: Use a dehumidifier in basements and address crawl space moisture; see crawl space encapsulation.
- Seal gaps: Add door sweeps and caulk cracks along the foundation and sill.
- Move hiding spots: Keep boards, stones, firewood, and flowerpots away from the house.
Frequently Asked Questions
Are pill bugs insects?
No. Pill bugs and sow bugs are crustaceans, related to shrimp and crabs, that live on land.
What’s the difference between pill bugs and sow bugs?
Pill bugs roll into a ball when disturbed; sow bugs can’t and have two small tail-like appendages.
Why are there roly-polies in my house?
They come inside when their outdoor habitat gets too wet or too dry. Large numbers indoors usually point to a moisture problem.
Are pill bugs harmful?
No. They don’t bite, sting, spread disease, or damage homes.
How do I get rid of pill bugs?
Reduce mulch and leaf litter near the foundation, fix drainage, dry out damp areas, and seal gaps.
