Bed bugs are essentially little bugs that are nocturnal and feed off human blood. There are actually a lot of different kinds, including some that feed off certain types of animals like chickens, but the ones most people are worried about live mainly off humans. They usually live inside of mattresses, where they have convenient access to a food source - you. They crawl out just before dawn and bite you, sucking out blood for about five minutes. You don't feel anything until after the bed bug is already safely back in its home.
They will usually bite once a week or so, and they can actually live for a long time without feeding - usually six months, but sometimes over a year.
Bed bugs can infest all kinds of different places in your bedroom. Most often they're in the mattress - in the seams, the box springs, or sometimes the linens. However, they can really be anywhere near where people sleep - furniture within crawling distance, carpet, books, phones - they've been found in all kinds of random things, because they don't create a nest, they just hide somewhere.
Bed bugs used to be nearly completely eliminated in the United States, Canada, and Western Europe - largely because of DDT and because of certain chemicals used against roaches. In recent years, however, there have been rising levels of infestations because
Can bed bugs hurt me? No, they aren't actually dangerous. However, the bites are annoying and they can cause skin irritation and rashes, especially if you've got a lot of them in the mattress. So it's always a good idea to get rid of them - because each bug can lay four or five eggs a day, leading to a pretty big batch of them if you leave things alone.
Quick summary on bed bugs: They are reddish-brown, flattened, oval, wingless insect and are up to 1/4 of an inch long. Nymphs must feed on blood to grow, shedding skins as they develop in a process called molting. They infest all types of facilities and living environments, even the most expensive, luxurious homes. Sanitation and cleanliness have no bearing on their presence.