Woodlouse identification and treatment

The woodlouse, also called “sow bug” or “wood bug”, is likely a regular visitor in your garden and on your deck. And although the presence of woodlice may be disturbing if they make their way into your basement, it’s not necessary to use pesticides to get rid of them.

The real problem with having woodlice in the house is that it’s usually the sign of an unwelcome humidity problem. They can’t survive in dry conditions, so by fixing the situation at the source, you should be able to say goodbye to these nuisance bugs.

But wait: Is this bug really a bug?

Because it looks like an insect in many respects, we often think of the woodlouse as a bug. In fact, it’s a crustacean, of the order Oniscedea, and it’s the only crustacean that doesn’t live in water. This explains its inclination to thrive in damp environments around your house and yard.

In Quebec, there are about 150 species, while there are about 3,500 different woodlouse species around the world. Some of them roll into a tight ball when threatened, which is why people sometimes also call them “pill bugs”.


The woodlouse measures between 10 and 15 mm and is equipped with seven pairs of legs. It has a segmented grey, black or brown exoskeleton. These plates fit together in a way that offers the crustacean greater flexibility of movement than its water-bound and harder-shelled cousins, the shrimp and lobster.

Young woodlice are hatched in batches of about 24 to 28, after being carried in the mother’s marsupial-like incubator pouch for about a month. The whitish offspring emerge with only six pairs of legs; the seventh pair usually appears at the first moult.

Woodlice have a life span of about 2 to 3 years and can reproduce from the age of 3 months.

Where you’ll find woodlice

Like many insects, woodlice that get into a house look for the darkest, most damp nooks and crannies. Consequently, you’ll most often find them in basements or unfinished cellars.

Outside the house, wood bugs hide in places where daylight can’t reach them:

  • Under dead leaves and wood
  • In fungi and mold
  • In decaying organic matter
  • In house foundations
  • Under and between rocks

Their presence in the garden can even be beneficial. As they eat dead leaves and decayed wood, they are effectively composting these organic materials and increasing soil fertility.

Unfortunately, they can also feed on any fruits and vegetables you may be growing in moist soil. When you think of a woodlouse munching away on your strawberries, squash and pumpkins, the urge to look at woodlice extermination becomes real.

You can rest assured, though, that these intruders aren’t dangerous; they don’t bite and they rarely carry harmful diseases.

A few words about woodlice extermination

If you’re noticing an unsettling number of these tiny crustaceans, the first thing you need to do is improve the humidity levels in your house. There’s no such thing as a woodlouse insecticide, and even if you use powders or sprays intended for other insects, the woodlice will just come back if you don’t fix your humidity problem.

The best way to start is to do a thorough inspection of the interior and exterior of your home. A simple dehumidifier in the basement is sometimes enough to solve the problem.

If you have a water leak or you find decaying wood in your house, act quickly to rectify the situation—if you don’t, other damp-loving pests such as carpenter ants, centipedes and silverfish will soon appear.

Be careful! Mould can also develop in damp areas, putting you and your family at risk for respiratory problems.

Prevention advice

You can prevent moisture problems around and inside the house by:

  • Making sure your land drains properly (no standing water near house foundations)
  • Removing any dead wood and leaves or other decaying organic matter laying around the house
  • Trimming shrubs growing near outside walls to ensure better air circulation
  • Filling holes and small cracks in foundations
  • Inspecting firewood before bringing it into the house
  • Using a dehumidifier in the basement in the summer to keep the relative humidity below 60%
  • Ensuring the optimal operation of your ventilation and heating systems

Following these few simple guidelines is usually enough to solve a woodlouse infestation. However, if the problem just won’t go away, contact Elite Pest Control.

Our extermination professionals are licensed with the Régie du Bâtiment du Québec, which means we can carry out pest-prevention work on your home, including sealing all openings and cracks that let in undesirable insects.