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Sowbugs, millipedes and centipedes

Quick facts

  • Sowbugs, millipedes and centipedes are not actually insects, but are arthropods related to insects.
  • They are NOT harmful to people, food, clothes, furniture, or other items within homes.
  • They are found in moist, decaying leaf litter or other organic material found around building foundations.
  • Outdoors, they are beneficial as they feed on other insects and recycle decaying organic matter.
  • Tolerate sowbugs, millipedes and centipedes when possible.
  • Even if they are numerous, use pesticides only if none of the other methods work to control them.

How to identify them

A transparent brown sowbug with overlapping plates on its back
Sowbug

Sowbugs

The sowbug is related to lobsters, crabs and crayfish.

  • It is brownish-gray and may be ¾-inches long.
  • It has fourteen legs, an oval shape and overlapping plates on its backs.
  • It feed on decaying organic matter.
  • The sowbug can survive only in damp places.

Sowbugs do not normally survive within a home because they need decaying organic matter in a damp location, like a basement.

A black worm-like millipede with several segments and numerous legs
Millipede

Millipedes

The millipede is a dark brown, worm-like creature with up to 400 very short legs.

  • 2 pairs of legs per body segment
  • Moves slowly.
  • 1 to 1 ½ inches long.
  • Curls up tightly when touched/handled, or after it dies.
  • Feeds on decaying organic matter.

Millipedes are most active at night and hide beneath objects where it is dark and damp.

Centipedes

The most common centipede is called the house centipede.

  • More than 1 inch long fully grown.
  • Flattened brownish or grayish-yellow body.
  • Sometimes marked with three dark stripes.
  • 15 pairs of long, jointed legs that are striped.
  • 2 long slender feelers extend from the head.

Stone centipede

They are found under mulch, leaves, loose bark, stones and similar sites.

  • Up to 13/4 inches long
  • Feed on insects, spiders and other arthropods (like sowbugs and millipedes) that live in the ground on the soil surface.
  • Harmless to people.
Brownish-yellow centipede with three longitudinal stripes across its back
Centipede
A shiny brown insect with several pairs of legs and two long antennae
Stone centipede

Behaviors

Sowbugs and millipedes

They crawl into homes from the soil and leaf litter, during late summer and fall and occasionally during spring and summer.

  • In the fall, millipedes and sowbugs seek protected places to overwinter.

  • If there is excessive rainfall or ground moisture, they may look for areas with less moisture.

  • Enter through cracks in foundations, around ground-level windows and under doors.

  • Commonly found in basements.

  • Rarely seen indoors during winter.

  • Found indoors in early spring as they emerge from cracks and crevices where they spent the winter.

Centipedes

  • Found in damp conditions and seen inside homes in warm weather.
  • They move indoors during spring and summer and are rarely seen in winter.
  • Move quickly and are usually noticed running across a wall, ceiling or open room toward a dark area.
  • May stop abruptly and remain motionless before they suddenly begin running again.

Centipedes are beneficial predators

  • Feed on small, living creatures such as insects, spiders and other arthropods, like sowbugs and millipedes.
  • Use poison-filled jaws to subdue their prey.

Centipede bites

Bites by a centipede are rare because it is very shy and the jaws are too small to break through human skin.

In case of a bite, some swelling may be seen, but the pain should not be severe.

How to get rid of sowbugs, millipedes and centipedes

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Jeffrey Hahn, Extension entomologist and Mark Ascerno, former Extension entomologist

Reviewed in 2018

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