These are undeniably the most diabolical bugs in existence. The house centipede is a creature of evil, a twisted parody of life, dwelling in the dark and dank places of the earth, glorying in death and decay. Scutigera coleoptrata, they belong to phylum Arthropoda (along with insects and crustaceans), subphylum Myriapoda (many legs, myriad meaning ten thousand, poda from Greek pous, foot.) The myriapods include centipedes, millipedes, pauropods, and symphylans, all of which are crawly things with far more legs than any righteous being. House centipedes are scutigeromorphs, which are the only class of centipedes with faceted eyes, while other centipedes have simpler eyes or none at all. When fully grown, house centipedes bear fifteen pairs of legs, which are long (long enough that at first glance they can be mistaken for spiders) and allow these vile and disgusting wretches to scurry with surprising speed to hide behind bookshelves and under your covers, where they wait to attack with their poisonous fangs.
That's right - as if it weren't enough for these denizens of filth to walk upon thirty legs, they have poison fangs. Admittedly, their attack is not terribly dangerous to humans, though, except in rare cases of allergy; a bite from a house centipede is comparable to a mild bee sting. They inject their prey - spiders, termites, and cockroaches, along with other household pests - with venom before eating them. As a matter of fact, if indeed your house is filled with them (and it probably is) they might be working to keep the other repulsive things infesting your house at bay. So you may choose to allow Satan's minions to infest your house if you wish to contract with the Devil to rid your habitation of the other creatures making a home amidst your filth. You'll just have to live with the knowledge that they're crawling over you while you sleep, and assuredly plotting against you.
How can I identify them, so as to righteously slay them?
First, if you are ridding the Earth of these repugnant vermin, you are doing the Lord's work. They grow up to an inch and a half in length (four centimeters or so) and have brown or yellowish bodies with three dark stripes. They are segmented, and each segment has a pair of legs, as few as four pairs at hatching but more every time they molt. Their long, thin legs have dark and light bands on them, should you foolishly bend close enough to examine them.
Their hindmost legs are extremely long, up to twice their body length, and they use them to catch their prey and hold it while they inject venom. Sometimes, they can be seen feeding on the innards of one insect while holding several others in their many legs.
Where do these iniquitous things come from?
When Lucifer was cast out of Heaven by God, he became Satan and ruled over Hell where he sets himself against all that is good and pure. He took God's creation of life and twisted it, mocking the Lord by perverting His work into these loathesome, malevolent creatures.
He first set them free to torment humanity in the Mediterranean, but they've spread throughout Europe, Asia, and North America. They entered North America through Mexico, and now they inhabit most of the United States. When outside, they live in the sort of place one expects to find centipedes: piles of leaves, rotting wood, and other dark, damp places. However, they are quite content to live their entire life inside your house, lurking in your basement until they attack. They can live for several years, and reproduce at a prodigious rate.
In your house, expect to find them in your walls, in basements, in crawl spaces, and in dark corners of your bedroom. They're also found sometimes in bathrooms, as they seek out sources of water. Generally, they live in damp, silent, sheltered areas, until you find them inexplicably crawling across your bedroom ceiling. From there, they wait until you're asleep to drop into your open mouth or crawl into your pajamas.
Enough about finding them. I want to commit mass murder.
It's not easy to kill these things, as Beelzebub endowed them with his own unholy strength. It takes a serious squishing; a mere smack with a shoe doesn't usually do them in. And pesticides don't work well against them, which means that to control these wicked creatures you might need to apply dangerous amounts of chemicals. Should you use them, the most effective are the carbamate pesticides; they should be applied around the foundation of the house and in other areas where they like to sneak in.
If you have substantial numbers of them, the best starting place is to remove the things that make your house hospitable to these minions of the Prince of Darkness. Clean up the various piles that they hide in, make sure your basement is dry, and avoid leaving standing water as much as possible. Seal up cracks where they enter; don't store large piles of firewood inside (they sneak in under the bark.) Add ventilation to dry up damp areas, and keep piles of leaves, bags of trash, and other shelter for them well away from the house. They don't eat human food, but some of the insects they feed upon do, so keep your place clean and uncluttered if it's infested with them. No scientific studies exist to measure the effect of holy water or the intervention of priests upon their numbers.
Why does God permit these creatures to torment us?
That God has not rid the earth of these unspeakable horrors from beyond can only be construed as a sign of His displeasure. He knows what you do at night when everyone else is asleep. You pervert.
Sources
The Holy Bible
http://www.ipm.iastate.edu/ipm/iiin/housece.html
http://www.uark.edu/depts/entomolo/museum/house_centipede.html
http://ohioline.osu.edu/hyg-fact/2000/2067.html
http://www.ento.psu.edu/extension/factsheets/centipedeHouse.htm
http://faunanet.gov.au/wos/factfile.cfm?Fact_ID=98
http://www.math.umd.edu/~schris/scutigera.shtml
A couple really icky pictures of the wicked little things can be found at http://bugguide.net/node/view/19023.