Centipedes, millipedes, sowbugs and pillbugs

What are they?

Centipedes, millipedes, sowbugs, and pillbugs are arthropods (not insects), although they do enjoy the same living conditions as insects. These creatures are not harmful. They are merely unattractive and considered a nuisance, especially when found indoors.

Sowbugs and pillbugs

Sowbugs and pillbugs are less than 2 cm (.79 inches) long and are usually dark to slate gray. They are armadillo-like and belong to the same class of animals as lobsters and shrimps. These tiny land crustaceans need moist conditions to survive, and like to live under rocks or debris where they feed on decaying organic matter. They usually die quickly once inside homes because moisture levels are not high enough for them.

Alternate Formats

Millipedes and centipedes

Wormlike millipedes and centipedes both have many body sections and many legs. However, the centipede has a more flattened body and only one pair of legs per section, while the millipede's body is rounded on top with two pairs of legs per section. Also, the centipede's legs are much longer, allowing it to move more quickly. When disturbed, millipedes tend to coil up, but centipedes swiftly run for the closest dark hiding place.

Centipedes are an efficient way of controlling other insect pests in your home.They like to eat spiders, bed bugs, cockroaches, silverfish, carpet beetles, or ants. Millipedes, on the other hand, do not survive once in the home because it is too dry for them.

Did you know?

Originally from Mexico, house centipedes are now among the most common centipedes in North America. They will invade houses if the sub-floor, drains, basement, or bathroom areas are overly damp. They will also come indoors in the fall when the weather turns colder. They have 15 pairs of legs and long antennae, and are about 2.5 to 5.0 cm (1 to 2 inches) long. House centipedes can move quickly and will hide in cracks, crevices, and behind baseboards. They sometimes like to hide under the bark of firewood stored inside the home.

Should I be concerned?

Although all centipedes have poison glands that open through their jaws, most house centipedes are not able to penetrate human skin with a bite. However, the few that can will give an effect similar to a mild bee sting, with symptoms generally disappearing within a few hours. The house centipede's bite will not cause any serious harm to pets like dogs and cats.

Sowbugs and pillbugs can sometimes enter damp areas of your house in large numbers. However, they do not bite, sting, or transmit diseases, and they don't infest food, clothing, or wood.

Sowbugs, pillbugs, and millipedes break down organic matter, releasing nutrients to garden plants. Centipedes help control other insect pests. For these reasons, this group can be considered beneficial and should be tolerated as much as possible.

A persistent infestation of sowbugs, pillbugs, or millipedes indoors may indicate a serious moisture problem within your home, and the presence of a food source like rotting wood.

How can I get rid of them?

Physical control

It is best to reduce the source of infestation outside your home first.

Did you know?

Sowbugs cannot roll up into a tight ball like pillbugs. Also, the sowbug has two tail-like appendages that the pillbug does not have.

  • Make sure the ground slopes away from your house to avoid water and moisture retention near the building foundation.
  • Remove leaf litter and decaying vegetation around the foundation of your home. Other objects providing hiding places on the ground (like stones, boards, or boxes) should be moved away as well.
  • Use coarse (instead of fine) mulches that allow water to drain.
  • Foundation plantings should be pruned and cleaned to improve ventilation around your home.
  • Allow the soil to dry between waterings.
  • Repair cracks in foundation walls or around windows before the fall.
  • Indoors, use a dehumidifier or a small electric fan to dry out damp areas in the basement.

Chemical products

Important!

If you use a pesticide to control your pest problem, read the label to make sure you are choosing the right product for the right pest. Follow all label directions and warnings carefully. Always look for a Pest Control Products (PCP) number on the label so you know the product has been approved by Health Canada. See Use pesticides safely for more information on using pesticides safely

Changing the habitat of these creatures outside your home should reduce their numbers. If these efforts do not control them well enough, you may choose to use a registered domestic-class pesticide product (which you can apply yourself). Note that using a pesticide indoors to control millipedes, sowbugs, or pillbugs is not recommended as they will soon die from dehydration once indoors.

  • Diatomaceous earth, an active ingredient found in many domestic pesticides, is an ecological means of control. It is a fine powder made from crushed microscopic marine fossils. As insects crawl over the powder, their outer "skin" is scratched, causing them to dehydrate and die. Diatomaceous earth will remain active as long as it is kept dry. It is non-toxic to humans and pets, but be careful not to inhale the dust when applying this product. This powder can be used in cracks and crevices as an ongoing control measure.
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