Sowbug: All You Need to Know – Your Friendly, Essential Guide

Sowbugs are fascinating little creatures that you might have come across in damp areas around your home or garden. Belonging to the Porcellio species, sowbugs are not insects but actually crustaceans, more closely related to crabs and shrimp Common Insects and Mites: Sowbugs, pillbugs, and millipedes. These gray critters prefer very damp environments and have an oval shape, sporting overlapping plates on their backs.

They may be small, but their biology is quite unique, which sets them apart from many other creatures you typically find around your home. These crustaceans have fourteen legs and are equipped with two pairs of antennae Sowbugs, millipedes and centipedes | UMN Extension. By getting to know more about sowbugs, you can better understand their habits, where they are likely to be found, and how to manage their presence if necessary.

Understanding Sowbugs

Sowbugs are fascinating crustaceans that have adapted to live on land. They have a unique appearance, resembling small armadillo bugs. Here’s what you need to know about these interesting creatures.

Their size varies, but they typically measure between 1/2 to 3/4 inches long. Sowbugs have a flat shape with a convex back and a flat belly. Their armor resembles that of an armadillo, giving them a distinctive look.

One notable feature of sowbugs is their seven pairs of legs. These legs help them move around in search of decaying organic materials to feed on. You’ll also notice a pair of antennae on their heads, which aid in their sensory perception.

Here’s a quick comparison table of common crustaceans:

Crustacean Size Appendages Distinctive Features
Sowbugs 1/2 to 3/4 inches long Seven pairs of legs, one pair of antennae Armadillo-like armor, gray in color, flat shape
Pillbugs 1/2 to 3/4 inches long Seven pairs of legs, one pair of antennae Can roll into a ball, bluish-black color

Now let’s list some more characteristics of sowbugs:

  • They prefer damp areas to live in.
  • They are nocturnal creatures, mostly active at night.
  • They don’t have a stinger or venom.
  • They are harmless to humans and pets.

By understanding sowbugs, their unique appearance, and their behavior, you can appreciate the role these crustaceans play in breaking down organic matter in our environment. So next time you encounter a sowbug, take a moment to observe its interesting features and habits.

Sowbugs Vs. Pillbugs

Sowbugs and pillbugs are small, gray, and oval creatures that are commonly found in moist areas around your home. While they might look similar, there are some key differences between the two that you should be aware of.


  • Have two small, tail-like appendages at the rear end of the body
  • Can’t roll up into a ball
  • More commonly found in damp, outdoor areas
  • Also known as woodlouse or slater


  • Do not have tail-like appendages
  • Can roll up into a ball when disturbed, hence the nickname “roly-poly”
  • Sometimes find their way indoors
  • Closely related to sowbugs but physically quite distinct

Here is a simple comparison table to help you differentiate:

Characteristic Sowbugs Pillbugs
Appendages 2 tail-like appendages None
Rolling Can’t roll into a ball Can roll into a ball
Habitat Mostly outdoor, damp areas Indoor & outdoor
Nicknames Woodlouse, Slater Roly-poly

Both sowbugs and pillbugs belong to the same crustacean family and are more closely related to lobsters than insects. They both require moisture to breathe, as they have gill-like structures to extract oxygen from the air.

Now that you know the primary distinctions between sowbugs and pillbugs, you’ll be better equipped to identify these small, gray creatures when you come across them in your surroundings.

Growth and Development of Sowbugs

Life Cycle

Sowbugs go through a fascinating life cycle. They start as eggs, which are carried in a special pouch called a marsupium. Within this pouch, the eggs hatch into young sowbugs that resemble smaller, paler versions of adults. These juveniles remain in the pouch for up to two months after hatching.

As they grow, they undergo several molting stages. This process takes about a year before they reach adulthood. Adult sowbugs are typically gray in color and 1/2 to 3/4 inch long. They have the ability to reproduce and lay eggs, allowing the cycle to continue.

Diet and Habits

Sowbugs possess an essential role in maintaining a healthy ecosystem. They are scavengers that feed on organic debris, such as:

  • Decaying plants
  • Organic waste
  • Decaying matter
  • Decaying organic matter

This diet helps them break down organic materials, contributing to a rich and fertile soil. Besides, their behavior is mostly nocturnal, which means they’re active mainly at night.

During the day, you’ll find sowbugs concealed in damp, dark places like under flower pots, outdoor rugs, and in leaf litter. Sowbugs possess gills, so they require moist environments to breathe effectively.

To summarize, sowbugs play a crucial role in the ecosystem by consuming decaying organic materials and facilitating the recycling of nutrients. By understanding their life cycle and behavior, you can appreciate these unique creatures and the essential role they play in nature.

Dwelling Places of Sowbugs

Indoor Infestations

Sowbugs can infiltrate your home, finding shelter in damp areas. For instance, basements providing the moisture sowbugs crave are prime spots for infestation. They may enter through cracks, openings, and crawl spaces, especially if there is humidity or a leaky pipe nearby. In damp garages, you might also come across these critters hiding among your belongings.

Outdoor Habitats

You can easily spot sowbugs in gardens, taking advantage of the naturally damp environment. They enjoy hiding under mulch, soil, compost, or leaf litter where moisture is retained. Sowbugs may also be found beneath rocks, stones, logs, and flowerpots at ground level. To sum up, the key places where sowbugs dwell include:

  • Damp basements
  • Garages with moisture issues
  • Gardens
  • Under mulch, soil, and compost
  • Beneath leaf litter, rocks, logs, and flowerpots

Taking note of these dwelling places can help you identify and manage sowbug populations in and around your home. Remember, these creatures prefer damp areas, so keeping your living spaces dry is a good preventive measure.

Prevention and Control of Sowbugs

Sowbug Prevention

To prevent sowbug infestations, you can take several measures. First, address any moisture issues in your home. This can include fixing water leaks and using a dehumidifier to reduce humidity. Keep your outdoor space clean and clear of decaying organic matter, such as fallen leaves and mulch, as sowbugs are attracted to these environments.

Seal any gaps or cracks that might allow sowbugs to enter your home. Use caulk around door and window frames, or apply expanding foam to fill any larger gaps. Additionally, make sure foundation areas are well sealed, as sowbugs often crawl up under the siding. Screens on vents and windows can also help keep them out.

Some examples of sowbug prevention measures include:

  • Fixing leaks in pipes and roofs
  • Using a dehumidifier in damp areas
  • Sealing cracks and gaps in foundations
  • Installing screens on vents and windows

Sowbug Treatment

If you have a sowbug infestation, it’s essential to act quickly to control the nuisance. Treating sowbugs outdoors involves applying granular pesticides like deltamethrin, lambda-cyhalothrin, or permethrin around your home’s perimeter in late summer or early fall. Remember, treatment will be less effective if food and shelter sources are still available near the foundation.

For indoor infestations, you can use a vacuum or sweep to remove the pests, as they usually die soon after entering due to lack of moisture. However, if the problem persists, it’s advisable to consult a professional pest control company like Orkin for specialized treatment. They will likely use chemicals and insecticides to eradicate the sowbugs.

Here’s a comparison table of prevention vs. treatment methods:

Prevention Treatment
Fixing leaks and reducing dampness Application of granular pesticides
Sealing gaps and cracks Vacuuming or sweeping
Clearing decaying organic matter Hiring a professional pest control service

Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Sowbug infected with Iridovirus


purple bug
July 11, 2009
Hello, we have purple bugs. They’re what we call potato bugs here in Michigan, but I see that on this site a potato bug is something else. Anyway, they are normally brown, but many of them are purple now.
Any ideas?
Western Michigan

Wood Louse infected with Iridovirus
Wood Louse infected with Iridovirus

Hi Kris,
This is the second time we have received a photo of a blue Sowbug or Wood Louse.  Sow Bugs are sometimes called Pill Bugs because they roll into a ball.  When a Sowbug is infected by a certain iridovirus, it turns blue.  Here is what the Woodlice Oddities Page has to say:  “Blue Woodlice An iridovirus can infect woodlice and at advanced stages of infection virus accumulates in such large numbers that it forms crystallinel structures in the diseased tissues. These crstalline structures give an intense blue or purple colour to the woodlice.
Individuals infected to this extent will usually die within a short time.”

Letter 2 – Legalities of Sow Bug Commerce in California


Subject: Legalities of sow and pill bugs in California.
August 8, 2015 2:54 pm
Is it legal to sell and buy sow and pill bugs in California.
Signature: Andrew smith

Pill Bugs
Pill Bugs

Dear Andrew,
To the best of our knowledge, there is no state law prohibiting the sale or purchase of Pill Bugs, Sow Bugs or Woodlice in the state of California, but there may be local laws.  We cannot fathom why a person would want to buy or sell Pill Bugs in California or elsewhere.  We have used an image of Pill Bugs from our archives to illustrate your query.

People have been using them for reptile food. But more importantly they’re being used in their terarriums to keep mold bacteria and such things under control. So kinda like a live in cage cleaner.

Letter 3 – Sow Bugs


Please help identify these home invaders
I have browsed through the common millipedes/centipedes and pantry beetles as suggested and haven’t quite been able to identify the insect invading my home. I believe it may be a centipede. These bugs first appeared en mass (about 40 found in half an hour) in my Toronto home at the end of March. They are very slow and ball up in their hard shells when approached. I do not believe them to be pantry beetles as I do not find them in my kitchen. They seem to be coming in from under the spare room (where there is no basement)where it attaches to the main house. I have hopefully filled the cracks now but would really like to know what these are so I can better prepare to defend my home. I apologize in advance that the 3rd picture is a bit blurry. Thank you,

Hi Karen,
These are not insects but Crustaceans. They are Terrestrial Isopods commonly known as Pill Bugs or Sow Bugs. Children sometimes call them Rollie-Pollies. They are more of a nuisance than a problem.

Letter 4 – Sow Bugs


My Fiancé hates these things
We’ve had these crawling around our basement here in Bloomington MN for the last few weeks. Any idea what they are and how to get rid of them?
Thanks, Chris

Hi Chris,
These are Sow Bugs, terrestrial Isopods. They proliferate in dark, damp areas.

Letter 5 – Sow Bugs


I live in the Northeast and I having a problem with these black bugs in my basement. I always thought they were called potato bugs but when I looked for a picture of potato bugs on the net, I realized that the bugs in my basement are something else. I would like to know what they are called. The are black. They have a shell-like back. They roll into a perfect ball when they are touched. They don’t bite. I use to play with them as a child. I have not seen them in the winter months. However, somehow, they find there way in my home when the weather breaks. Do you know if they have a name?

Dear Connie,
It sounds like you are describing Sow Bugs or Pill Bugs. These are not insects but Isopods, a group of Crustaceans. They are often numerous in damp places including basements and gardens. They are called Pill Bugs because of their habit of rolling into a ball. The Common Pill Bug, Armadillidium vulgare, is dark in color, often approaching black. They are omniverous, and feed on young and decaying plant material. Unless very numerous, they do not make significant damage. They have few predators because of a distasteful secretion, but a spider, the Sow Bug Killer, is a natural enemy. Here is a photo we just took in our garden.

Letter 6 – Sow Bugs


Dear WTB,
I encountered a different looking bug this morning, and have been trying to search the net for pictures, but have been unsuccessful, and was hoping you could help. The body of the spider was an oval-oblong shape and beige, or tan in color, and the head was small and red and the legs appeared to be coming out in between the head and body and they were also red in color. I thought it a little strange that the legs were not spread out along the body. I live in the Denver Co. area, if that helps. Any photos would be great too.

Dear K,
That is the second letter today with the same spider. The other was from the UK. You saw a Sow Bug Killer, Dysdera crocota. They are one of the few predators that will eat sow bugs which have an unleasant taste. They sometimes bite people, but the bite is not serious. They are beneficial.

Thank you for your reply. Would you happen to have a photo of the sow bug
killer? I have tried looking for one, but cannot find one.
Thank You

Hi K,
I’ve enclosed the photo. Let us know if that was your spider.

Sorry for the delay.
That is the spider.
Thanks for your help.

Letter 7 – Sowbug


whats my bug
I have this bug in my house and I see the out side as well. They are usually under rocks and plant pots or in the hidden places like under a couch or chair. They have 6 legs on either side, 2 little hair-like spikes on it’s hind end, and anouther 2 anntenas on it’s head. They are always a grayish colour. These two pictures are the largist I have ever seen (aprox.1cm).

You have a terrestrial isopod commonly called a Pillbug, Sowbug or Rollie-Pollie. They are relatively benign, though they can get very numerous.

Letter 8 – Sowbug


Subject: House Bug – Is it a Bed Bug?
Location: Washington DC
November 13, 2013 9:00 pm
I found this on my wall, and poked it with my finger. It left a lot of liquid on the wall, making a stain. It is smaller than my smallest nail, maybe 4 mm.
Signature: DC Bugsy


Hi DC Bugsy,
This is a benign terrestrial crustacean commonly called a Sowbug.  You can read up on Sowbugs on Texas A&M Agrilife Extension.

Awesome, thank you for the reply! I love this site, and will donate tonight 🙂

Letter 9 – Sowbugs


Subject:  Mystery Bug
Geographic location of the bug:  Mid Michigan
Date: 08/23/2021
Time: 01:55 PM EDT
Your letter to the bugman:  These bugs were found on tree limbs that had been cut. I can’t find anything that says what they are.
How you want your letter signed:  unsure what this means


Dear Unsure,
These are Sowbugs, Terrestrial Crustaceans that help break down decaying vegetable matter in the woods and garden.



  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

15 thoughts on “Sowbug: All You Need to Know – Your Friendly, Essential Guide”

  1. Holy wow. I never imagined a viral infection could become so severe that it could change the hue of an animal. Chilling!!!

    • You are correct that because of the agriculture industry, California has very strict importation laws and fruits, produce and plants. The inquiry seemed to imply buying and selling within the state and not the importation of Pill Bugs into the state.

  2. We too call them Potato bugs here in Utah. Ive heard people fro other areas call them rollie pollies, doodle bugs, or pill bugs. But around here they’ve always been called Potato bugs.


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