Centipedes are a type of arthropod with several pairs of legs. The common house centipede has 15 pairs of legs and measures more than an inch long, although its legs make it seem 3 to 4 inches long. Centipedes move quickly and have a frightening appearance, so many people dislike finding centipedes in the home. As long as you don't have a lot of centipedes, however, an occasional centipede isn't dangerous or problematic.
Centipedes transform through six larval stages before becoming adults. Female centipedes live for several years and produce up to 150 offspring. Centipedes prefer to hide in cool, dark locations, such as in floor drains, under cardboard boxes, inside cement block walls, in crawl spaces and beneath concrete slabs. Centipedes inject poison into their prey, but their jaws are not strong enough to bite humans in most situations.
Finding a centipede crawling out of your shower drain is alarming, but the occasional centipede in your home isn't a cause for worry. It probably wandered in from outside by accident or to escape hot weather. It's good to have centipedes outside your home, because they help control the population of other arthropods and insects. Centipedes that come into your home won't damage your food, furniture, clothing or possessions, and they won't bite humans unless they're pressed or squeezed.
If you have a lot of centipedes in your home, you probably have a lot of smaller arthropods and insects that are feeding the centipedes. Large quantities of centipedes aren't dangerous, but infestations of other arthropods or insects may be problematic. Controlling these pests will reduce the centipede population. Lots of centipedes may also indicate a humidity problem, because these arthropods require moist environments to survive.
If you have lots of centipedes, use sticky insect traps to find out what other bugs are in your home and take steps to eliminate those pests. In addition, reduce the humidity in your home by using a dehumidifier or grading the soil to slope water away from the basement. Seal cracks in the foundation and place screens over basement floor drains. Remove clutter, such as boxes and stacks of magazines. If other management methods are ineffective, applying an insecticide labelled for indoor use to baseboards and other hiding places will reduce the centipede population.