Bed bugs hatch from eggs and pass through five nymphal stages (instar) before becoming adults capable of reproduction. Nymphs and eggs are especially tiny, but still visible to the naked eye.
Adult bed bugs are about 3/16-1/4 inch long, broadly oval, flattened (when unfed), brown to reddish brown bugs. They have a 3-segmented piercing, sucking beak, which rests along their underside when they are not feeding. Females have a rounded abdomen and males have a slightly pointed abdomen. Bed bugs do not have wings and cannot fly, jump or hop. They have six long legs with claws at the end of each, making them well adapted to climbing rough surfaces. Bed bugs can move quickly. An adult bed bug can travel about 4 feet a minute and a nymph can travel about one foot a minute.
Bed bug eggs are tiny, pearly white and barrel shaped. They are about the size of a couple of grains of salt. Eggs are covered with a sticky substance that cements the egg to whatever surface it is laid on, making them difficult to remove.
Nymphs resemble adult bed bugs. Newborn nymphs are about the size of a poppy seed and are very pale, almost transluscent. Nymphs require at least one blood meal to molt, shedding their exoskeleton/shell, and move to the next level of development. They pass through five instars or nymphal stages before becoming adults. At each stage they increase in size and darken in color, becoming more similiar to an adult bed bug.
Both nymphs and adults change color and size after feeding, young nymphs or instars will turn bright red with blood and adults will assume a more reddish brown color.
In an infested area you will see (photos) adult bed bugs, nymphs of varying sizes and colors, as well as eggs, fecal droppings and the skin the nymphs cast off as they progress to the next stage of life.
Bed bugs are sometimes confused with other insects such as young cockroaches, carpet beetles or bat bugs.Your county agricultural extension service or pest control professional can provide positive identification.