What is a Centipede?
There are more than 2,000 species of centipede in the world, most of which live almost exclusively outdoors. The kind we're talking about is the house centipede, scientific name Scutigera coleoptrata, the only species that can live its entire life and breed inside a building. The species is probably native to the Mediterranean region, but has made its way around the world thanks to international trade and travel.
Centipedes are arthropods like insects, but they aren't actually insects, since they have more than six legs (by far; the house centipede has an average of 30 when full-grown). They lay eggs—usually between 50 and 100—in the spring, and can live a relatively long time: 3-7 years. They spend most of the day hiding in dark places, and come out at night to hunt for small prey. Because they have to remain in a damp environment to keep from drying out, they are often found outdoors under rocks, tree bark, and leaves, and indoors in basements and bathrooms.
Natural Centipede Control
Actually, most methods of getting rid of centipedes are natural ones. I'll provide a couple of additional suggestions here, but some natural solutions—like keeping your house dry and sealing potential points of entry—are detailed in the center of the page.
Reduce clutter, inside the house and out. If your laundry isn't on the floor, centipedes will be forced to find another hiding place. Outside, keep leaf litter, grass clippings, firewood, compost, and building materials cleaned up or away from the perimeter of the house. If you really hate centipedes (and you aren't renting), you may even go so far as to tear down any ivy growing up the side of your house. Centipedes love to hide in it.
If you want to poison the centipedes, but you don't want to poison the earth, yourself, or your pets, you can use natural pesticides like boric acid or food grade diatomaceous earth for continual centipede control. Products containing plant-derived pyrethrin will exterminate centipedes on contact, and can be used as a fog or spray.