When transiting from the nymph to the adult stages of their life cycle, bedbugs change their appearance from 1.5 millimeter long, translucent nymphs to 5 to 7 millimeter long, brown-colored bugs. Bedbug nymphs molt five times to become adults. Their eggs are tiny and white in color.
The eggs of bedbugs are approximately 1 millimeter in length or less. These eggs, which are about the size of a pinhead, have a pearl-white color. The naked eye can spot bedbug eggs that are over five days old.
In its nymph stages, the bedbug is small and translucent or pale yellow in color. The nymph is therefore able to remain invisible, unless it has fed recently. As the first-stage nymph feeds on a meal of blood and molts, it increases in size until it reaches a length of 4.5 millimeters in its fifth and final stage of development. Each time the nymph molts, its color darkens.
The adult bedbug is approximately the size of an apple seed. If it has not fed recently, it is brown with an oval, flat and long body. A recently fed bedbug is reddish-brown and appears elongated, with a balloon-like shape.
Adult bedbugs have antenna, hairs that are short and golden in color, and wings that the bugs do not use for flying. The nymphs look like smaller counterparts of the adults.