Extension Educator, Horticulture
This time of year some unexpected pests may appear in your home. However unlike your 27 year old son, they do not set up residency in your basement. They are more like your in-laws: they show up unexpectedly, stay a bit too long but are eventually a faint memory until next time.
Their presence may be alarming to us but many household pests including centipedes, millipedes, sowbugs and pillbugs are a mere frustration on the level of discovering an empty ice cube tray or finding the toilet seat up. Fortunately these pests are unlikely to cause harm to us, our pets or our homes.
Centipedes, and millipedes are not insects but in families all their own. Insects have six legs or fewer whereas centipedes never have fewer than thirty and millipedes despite their thousand leg name generally have only a few hundred at most. They are an engineering marvel in their ability to keep all those legs moving in unison.
Millipedes are hard-shelled, worm-like animals with many segments usually bearing 2 pairs of legs on each segment. Their legs are uniformly spaced along their body and ripple in waves as they move. The adults are 1-2 inches long and are brown, tan or gray. Millipedes curl up into a "C" when startled.
Our common centipede is grayish brown; about two inches long and has fifteen pairs of long skinny legs. Centipedes can inflict a painful bite but only if we deserve it by mishandling them. Millipedes don't bite but prefer the stinky route of predator deterrent.
Sowbugs, and pillbugs (also know as roly-polies) are also not insects. They are more closely related to barnacles, crabs, lobsters and crayfish. Like their kin sowbugs and pillbugs breathe with gills so it's no surprise they are found in moist areas and quickly die in our homes. Sowbugs are brown and glossy whereas pillbugs are dark grey. For inquiring minds an easy way to tell the difference is to disturb them. Sowbugs run away or lie flat. Pillbugs do the armadillo roll into a compact ball.
Centipedes, millipedes, sowbugs and pillbugs are creatures of damp dark places. Their preferred homes are outdoors under rocks, in leaf litter, logs, dead trees or mulch where they have important jobs as decomposers and predators. However occasionally they stumble indoors where it's usually not damp enough for them to live out their natural lives. Generally we find them curled up literally on their last leg.
In general for household nuisance pests the best indoor option is to remove them by vacuuming. Be sure to change the vacuum bag after each use. Their removal usually falls to the designated "spider squasher" in the family.
Since they like damp and dark places, discourage their entry by eliminating their desired habitat. Correct moisture problems in basements and crawl spaces. Remove nearby leaf litter, stones, and mulch from building foundations and keep shrubs trimmed away from the house. Also discourage and reduce entry into buildings by caulking and repairing cracks and crevices around windows and doors.
Outdoor foundation insecticide sprays show some management of nuisance pests. Look for these active ingredients on the insecticide label: permethrin, cyfluthrin, esfenvalerate, or bifenthrin. Spray the building foundation and a foot of the surrounding soil. Many ready-to-use indoor insect sprays can also be somewhat helpful but these pests usually die on their own indoors. Indoor insecticide sprays are marginally effective on these pests and are usually not necessary. As always read and follow all label directions and be sure product is labeled to be used indoors. Although we may feel like we have to control them a reasonable option is to ignore nuisance pests especially since most appear for a short time.
For more information and some great pictures of household insects check out http://urbanext.illinois.edu/bugreview/