Cimex lectularius, commonly known as the bed bug, is a small, wingless insect that feeds on the blood of humans and other warm-blooded animals. Adult bed bugs are about 4 to 5 millimeters long, with a flat, oval shape and a reddish-brown color. They are primarily nocturnal and tend to hide in cracks and crevices during the day, often in or near beds, hence their name. These pests reproduce quickly, with females laying up to 500 eggs in their lifetime. Bed bugs are not known to transmit diseases, but their bites can cause itching, discomfort, and allergic reactions in some individuals. Effective control measures include thorough cleaning, vacuuming, and the use of insecticides.