Bed bugs are small insects that feed on human blood. They are usually active at night when people are sleeping. The bite of a bed bug is usually painless, and a person may not even know that they have been bitten until a large itchy welt appears on their skin several days later. While these bites may be a nuisance, bed bugs do not transmit disease to humans.
Adult bed bugs have flat rusty-red-colored oval bodies. Adult bed bugs are about the size of an apple seed, they are big enough to be easily seen, but often hide in cracks in furniture, floors, or walls. When bed bugs feed, their bodies swell and become brighter red. They can live for several months without feeding on a host.