Pillbugs in California: Your Complete Guide to Roly-Polies
By the Clark Pest Entomology Team | Last Updated: November 11, 2025
Quick answer: Pillbugs—those little gray bugs that roll into balls—aren't actually insects at all. They're harmless crustaceans (basically tiny land-dwelling cousins of shrimp) that feed on rotting plant stuff. You'll find them under flower pots and damp mulch in California yards. They sometimes wander inside by accident, but they can't survive indoors and pose zero threat to you, your family, or your home.
Wait, Pillbugs Aren't Insects?
So here's something that surprises most people—pillbugs aren't bugs at all, at least not in the insect sense. They're actually crustaceans. Yep, the same family as crabs, lobsters, and shrimp. Hard to believe when you see one crawling under your garden pot, right?
Scientists call them Armadillidium vulgare, but nobody uses that name in real life. Most folks call them roly-polies, doodlebugs, or pill bugs. Some people even call them potato bugs, though that name gets confusing since it refers to different creatures depending on where you live.
The "roly-poly" nickname? That comes from their party trick—when they feel threatened, they curl up into a perfect little ball. It's their defense mechanism, and it works pretty well against birds and other predators.
Now, what makes them crustaceans instead of insects? They've got seven pairs of legs—that's 14 total—while insects only have six. They also breathe through gill-like structures called pleopods on their abdomen. That's why they need to stay in damp spots to survive. Without moisture, they basically suffocate.
What Do Pillbugs Actually Look Like?
If you've ever gardened in California, you've probably seen these little guys. They're pretty distinctive once you know what you're looking for.
Common pillbug showing its armor-like shell.
Photo: Wikimedia Commons (CC BY-SA 3.0)
They're small—about the size of a pencil eraser, maybe a quarter to half inch long. The color is usually slate gray, though sometimes you'll see them with a brownish or even slightly bluish tint. Their body is oval-shaped with this dome-like back that looks like medieval armor.
That armor is actually made up of overlapping plates, kind of like roof shingles. The plates let them curl up into that signature ball shape when danger shows up. It happens almost instantly—touch one gently and watch it go from bug to sphere in about half a second.
Baby pillbugs? They look just like tiny versions of the adults, except they're much lighter in color. Almost white or pale gray before their shell hardens up and darkens. Pretty cute, actually, if you're into that sort of thing.
Pillbugs vs Sowbugs: Can You Tell Them Apart?
People mix these up all the time. Makes sense—they look similar, hang out in the same places, and both are harmless. But there's one super easy way to tell them apart.
The test: Pillbugs can roll into a complete ball. Sowbugs cannot. That's it. That's the main difference.
| Feature | Pillbugs | Sowbugs |
|---|
| Rolling ability | Can roll into a ball | Cannot roll up |
| Tail area | Smooth rear end | Two little tail projections |
| Body shape | More rounded, dome-like | Flatter, more stretched out |
Both types are beneficial decomposers in nature. They're out there breaking down dead leaves and enriching your soil. From a pest control perspective, they act almost identical. If you're seeing lots of either one near your house, the prevention strategies are exactly the same.
Are Pillbugs Dangerous? Will They Hurt My Plants?
Short answer: No, they're not dangerous at all. They don't bite, they don't sting, they don't carry diseases, and they won't damage your house. In fact, they're actually helpful outdoors because they break down dead organic stuff and put nutrients back into the soil.
But What About My Garden?
Okay, this is where it gets a bit more nuanced. Pillbugs mainly eat dead and decaying plant material—fallen leaves, rotting wood, that mushy pumpkin you forgot in the corner of the yard. That's their preferred diet.
But sometimes, if their population gets really high or they run out of their favorite dead stuff, they might nibble on:
- Baby seedlings you just planted
- Young tender roots
- Strawberries or cucumbers sitting on the ground
- Overripe or damaged vegetables
The damage is usually pretty minor. More cosmetic than anything. If you're seeing serious plant destruction, it's probably slugs, snails, or earwigs—not pillbugs. The University of California Integrated Pest Management program even says pillbugs rarely cause real economic damage to crops and are generally beneficial as decomposers.
What About Kids and Pets?
Totally safe. Pillbugs are completely non-toxic. If your toddler picks one up (and they will, because kids love roly-polies), no worries. If your dog accidentally eats one while sniffing around the yard, also fine. They're actually popular classroom pets for elementary school science projects.
Where Do These Things Actually Live?
Pillbugs are everywhere in California—coastal areas, inland valleys, suburban gardens. The only place they struggle is really dry deserts. They love our Mediterranean climate, especially in urban and suburban areas where regular watering keeps things moist.
Their Favorite Hiding Spots
During the day, pillbugs hide in dark, damp places. They need moisture to breathe, remember? So they tuck themselves into little humid pockets. Check under:
- Flower pots and planters (especially plastic ones that trap moisture)
- Those decorative landscape rocks
- Mulch, leaf piles, or your compost bin
- Any wooden boards, logs, or that firewood stack
- Grass clippings you haven't raked up yet
- Dense ground cover like ivy
- Around your trash cans
At night, especially on warm humid evenings after you've watered or after it rains, they come out to wander around looking for food. That's when you might spot them crossing your patio or sidewalk.
How They End Up Inside Your House
They're not trying to move in. It's usually an accident. They wander through:
- Gaps under doors (sliding glass doors are notorious)
- Cracks in your foundation
- Openings around pipes or utility lines
- Unscreened crawl space vents
- Gaps around ground-level windows
Good news? They can't reproduce indoors. Without enough moisture, they die within a day or two inside your house. So if you see a few, it's not like you're about to have an infestation.
Why Are They Coming Into My House?
Usually means one of two things is happening outside:
Population explosion: If conditions are perfect out there—lots of moisture, tons of decaying plant matter, nice mild temperatures—pillbug populations can absolutely explode. When their outdoor hangout gets too crowded, they start wandering in search of new territory. Some inevitably end up at your door.
Weather changes: A sudden heavy rainstorm, you going crazy with the sprinklers, or conversely a really hot dry spell can all drive them to seek better conditions. They're looking for the right moisture level, and sometimes that search leads them right through your door threshold.
Seeing one or two inside occasionally? Normal. Nothing to stress about. Seeing dozens regularly? You've got a large outdoor population living way too close to your foundation.
How to Keep Pillbugs Out of Your Home
Best strategy is prevention. Since they die indoors anyway, the real goal is reducing the outdoor population near your house and blocking their entry routes.
Fix Your Moisture Issues First
This is the most important part. Pillbugs need moisture, so if you eliminate excessive moisture around your foundation, you eliminate most of the problem.
- Fix any leaky outdoor faucets, hoses, or sprinkler heads
- Make sure your downspouts and gutters direct water away from the foundation
- Water your lawn and gardens in the morning so everything dries before evening
- Fix drainage problems where water pools after rain
- Keep mulch thickness to 2-3 inches max—thicker mulch holds way too much moisture
Clean Up Your Yard
- Get rid of leaf litter, grass clippings, and dead plant debris regularly
- Move that firewood pile at least 20 feet away from your house
- Pull mulch back 6-12 inches from your foundation—create a dry barrier
- Put your flower pots on pot feet or bricks so air can circulate underneath
- Remove any boards, stones, or junk sitting directly on the soil
Seal Your House
- Install door sweeps on all exterior doors, especially the garage door
- Caulk or foam any cracks in the foundation
- Put fine mesh screening over crawl space vents
- Replace damaged weather stripping around windows and doors
- Fill gaps where utility lines come into the house
DIY Control Methods That Actually Work
For small pillbug issues, you can usually handle it yourself pretty easily.
Just Remove Them
If you're only seeing a few inside, grab a broom or vacuum and remove them. Since they can't survive indoors, that's often all you need to do. No chemicals required.
Make a Simple Trap
Old-school method that works surprisingly well. Take a hollowed-out potato half, a cantaloupe rind, or an orange peel. Put it near where you see pillbugs in the evening. Check it in the morning—they'll be hiding inside. Throw the whole thing away (far from your house) or dump them in your compost bin.
Try Diatomaceous Earth
Food-grade DE (not the pool stuff) can work as a perimeter treatment. It's basically ground-up fossils that damage the exoskeleton of pillbugs and make them dehydrate. Sprinkle it in a barrier around your foundation. Only works when dry, though—rain or heavy dew makes it useless. Penn State Extension recommends it as part of an integrated approach for occasional invaders like pillbugs.
What About Pesticides?
Generally not your first choice. Pillbugs are beneficial in gardens, and most indoor "invasions" are temporary anyway. If you do decide to use chemical control, only apply it outdoors where they congregate—under pots, along the foundation, in mulch beds. Always read and follow label directions.
When Should I Call a Pro?
Most homeowners can handle occasional pillbugs without help. But sometimes professional assistance makes sense:
- You're consistently finding dozens indoors even after trying prevention
- They're actually damaging your seedlings or garden plants significantly
- You've addressed moisture and sealed entry points but they keep coming
- You're not sure what the real problem is or need an expert to assess
- You want a comprehensive solution that addresses root causes, not just symptoms
A Clark Pest Control technician can spot moisture problems you might miss, find hidden harborage areas, and recommend targeted solutions using Integrated Pest Management techniques. We focus on long-term prevention rather than just spraying chemicals everywhere.
Need help? Give us a call at (800) 882-0374 or request your free inspection.
Clark's Expert Insight
"Here's a pro tip: if pillbugs are showing up inside regularly, grab a flashlight and check your foundation at night after you've watered your yard. Nine times out of ten, you'll see exactly where they're gathering—usually around a dripping hose bib, under that thick mulch pushed right against the house, or in planter boxes sitting flush with the wall. Fix those moisture spots and seal the nearby cracks, and your problem usually disappears within a week."
Common Questions About Pillbugs
Do pillbugs carry diseases?
A: Nope, pillbugs don't carry or spread any diseases that affect people or pets. They're harmless decomposers. Safe to handle, though washing your hands after touching any outdoor critter is always smart.
Why do they roll into a ball?
A: It's pure defense. When threatened, they curl up to protect their soft underside with their hard shell. The overlapping plates form a nearly perfect sphere that birds and other predators can't easily attack. Pretty effective strategy, really.
Can pillbugs damage my house?
A: No. They don't chew through wood to build nests like termites or carpenter ants. While they do munch on already-rotting wood in nature, they can't damage sound, healthy wood. If you see them near your foundation, it just means moisture conditions are favorable for them—not that they're destroying anything.
What do pillbugs eat?
A: Dead and decaying stuff—fallen leaves, rotting wood, compost, dead plant stems, grass clippings, decomposing fruits. They're nature's cleanup crew, breaking down this material and returning nutrients to soil. Sometimes when populations are high, they'll nibble tender seedlings or ground fruits, but that's opportunistic rather than their main diet.
Are they actually beneficial?
A: In outdoor environments, absolutely. They're nature's recyclers—breaking down dead plant stuff and enriching soil. They help speed up composting and contribute to healthy garden ecosystems. They only become a "pest" when they wander inside (where they die anyway) or when huge populations occasionally damage seedlings.
How can I tell pillbugs from sowbugs?
A: Easiest test ever—gently poke one. Pillbugs immediately roll into a tight ball. Sowbugs just run away but can't curl up. Sowbugs also have two little tail appendages sticking out their rear end, while pillbugs have a rounded back end.
Do they only come out at night?
A: Pretty much. During the day they hide in dark, moist spots to avoid drying out. At night, especially on warm humid evenings, they emerge to look for food and water. Want to see where your populations are concentrated? Check your yard with a flashlight about an hour after dark following watering or rain.
Will they go away on their own?
A: If they're inside, yes—they'll die within a day or two from lack of moisture. Can't establish indoor populations. Outdoor populations won't disappear unless you address what's supporting them—excess moisture, harborage materials, abundant food sources. Seasonal weather changes (hot dry summers) can temporarily reduce outdoor numbers naturally.
What eats pillbugs?
A: Lots of things—spiders, centipedes, ground beetles, birds (especially robins), toads, frogs, lizards. Some people encourage these natural predators as biological control. Even with predators around though, pillbug populations can still get large in favorable conditions since they reproduce quickly.