Adult bedbugs are about the size of an apple seed, or 3/16 to 1/4 inch long, notes the U.S. Environmental Protection Agency. They appear flat, brown and oval-shaped if they have not recently fed, but they look reddish-brown, elongated and balloon-like after feeding. Young bedbugs are smaller, translucent and white.
A bedbug is classified as a true bug because it has a beak with three segments, an antenna with four parts, and short, golden hairs, according to the EPA. They also have wings that they don't use for flying. Adult bedbugs produce a musty odor that originates from glands on the lower part of the body.