Identify Your Pest Crawling insects Sow bugs and pill bugs
Sow bugs and pill bugs
Oniscidea · Also called: Woodlice, roly-polies, isopods
Sow bugs and pill bugs are small, grey, armoured crustaceans that live in damp soil and leaf litter. People notice them when they wander into basements, window wells and entryways, which usually points to extra moisture nearby.
Size Up to about 15 mm long
Colour Slate grey to brownish grey, sometimes mottled
Key feature Oval, armour-plated back and 7 pairs of legs; pill bugs roll into a ball
Season Spring to fall; most often after snowmelt, heavy rain and in fall
Where Window wells, basement floor edges, door thresholds, mulch and flower beds
What it looks like
Sow bugs and pill bugs have an oval, slightly domed body covered by overlapping grey plates. They have seven pairs of legs and a pair of short antennae. They hide under objects during the day and come out at night.
To tell them apart, touch one gently. A pill bug curls into a tight ball about the size of a pea. A sow bug stays flat and hurries away. Look at the back end too: a sow bug has two short prongs sticking out, while a pill bug’s rear edge is smooth and rounded. Both are crustaceans, not insects.
Often confused with
Millipede
Bed bug
Signs to look for
Bugs in window wells
Dead bugs on basement floors
Activity near doors
Crowds under objects outside
Risks and damage
Sow bugs and pill bugs are mostly a nuisance. They are harmless to people and pets, and they eat rotting plant matter, not your home or belongings. Indoors, they usually dry out and die quickly. Outdoors, large numbers may nibble seedlings or ripe strawberries resting on damp soil. The main concern is what they point to: extra moisture near the foundation or in the basement.
In Alberta
Sow bugs are common around damp foundations, window wells and flower beds across Alberta, including Edmonton and Calgary. The kinds that cannot roll up are seen most often here. True pill bugs occur too, but less often. Indoor sightings rise after snowmelt, after heavy rain and in fall.
Sow bugs and pill bugs breathe through small plates under the rear of the body. These plates must stay moist to work, which is why the bugs dry out and die so quickly in a heated home.
How to keep them out
Dry out the foundation
Fix drainage
Clean and cover window wells
Seal entry points
Lower indoor humidity
When it is time to bring in a professional
Consider professional help if sow bugs keep showing up indoors in large numbers, or if you cannot find the damp spot drawing them in. A trained eye can find entry points and moisture sources around the foundation and window wells. Technica’s licensed technicians can inspect your home and recommend a plan that fits.
Frequently asked questions
Are sow bugs and pill bugs harmful to people or pets?
No. They do not bite, sting or carry disease, and they are not known to harm pets. They are mainly a nuisance and a sign of dampness.
Will sow bugs breed inside my house?
Rarely. They need steady moisture and decaying plant material to survive and breed. Most that get inside dry out and die. If they seem to be living indoors, there is likely a hidden leak or a very damp area worth fixing.
Why do I see so many after it rains?
Wet weather lets them travel farther without drying out, so more of them wander. Some reach the foundation and find gaps under doors or around basement windows.