The common bed bug, Cimex lectularius, is an insect that (in its adult stage) is roughly the size & shape of a flattened apple seed. Bed bugs leave the cracks and crevices where they hide during to day to feed on the blood of sleeping humans. Pest control experts believe that bed bugs will soon become the most serious household pests in the U.S. Bed bug infestations are extremely difficult (and costly) to eliminate but you can start by staying away from used furniture (especially beds).