Bed bug adults are 1/4 to 3/8 inch long and considerably larger when recently fed than when unfed. The female has a rounded abdomen tip, and the male has a spade-shaped abdomen. Adults are reddish brown or mahogany in color. They have no wings, but they do have wing pads. Antennae have 4 segments and are noticeably long, though not as long as those of a cockroach. Bed bugs have gradual metamorphosis, so nymphs appear similar to adults but smaller. The egg is about ¼ inch (2 millimeters) in length and bright white in color. Newly hatched nymphs are the same size as the egg and straw colored until their first feeding. Once fed, they are larger and look like a small drop of blood. Nymphs gradually gain a dark spot in their abdomens from blood meals. They turn darker red in color as they molt and age. There are 5 nymph stages. It is important to note that the eastern bat bug, Cimex adjunctus, common in the Northeast, looks like a bed bug but with some easy-to-see differences. Most obviously, bat bugs have much longer setae (hairs), especially on the pronotum, and appear much "hairier" than bed bugs. If you incorrectly identify the species of bed bug, then the treatment you propose will probably not be effective. Note the image to see this difference.

Bed bugs have 5 juvenile stages (in- stars) and need blood meals at each stage in order to grow. Additionally, they feed as adults and may feed several times at each stage. The life cycle can be as short at 4 weeks from egg to adult under favorable conditions, which are conditions that humans find comfortable. Bed bugs are cryptic, meaning they hide extremely well and can be difficult to detect or find Adults and nymphs form aggregations in areas with low disturbance, especially the headboard, bed frame, and box spring of a bed. They will also inhabit spaces behind molding, electric and switch plates, carpet edging, and gaps in other furniture. Females lay eggs in these areas. Fecal stains also appear in and around the outside of hiding spots. Bed bugs are sensitive to extremely wet or dry conditions and do not tolerate extreme heat. They can live for months without a blood meal (adults around 4 to 8 months, and nymphs up to 3 months), but they are vulnerable to dehydration when conditions are hot and dry. Cool temperatures will lengthen their life span.

Bed bugs feed on human blood and hide in cracks and crevices in the bedding of their hosts. They have stylet-type mouthparts to pierce the skin to tap into a blood vessel. Bed bugs may insert their mouthparts into the skin several times before feeding. Sufferers sometimes awake to find hundreds of bites on their bodies. The resulting bites vary greatly among people, from no reaction at all to severe swelling, blistering, and very rarely, anaphylaxis (life-threatening allergic reaction). While bed bugs have never been shown to transmit disease organisms, their bites may result in secondary infections. Much is still unknown about bed bugs' potential to help spread disease. The most obvious and significant health effects that bed bugs have on their victims are the fatigue, stress, anxiety, depression, and other mental conditions that many people experience. Although not well understood today, the mental health impacts of bed bugs are thought to be significant. This is also true for some who are just fearful that they have them or could get them. The financial burdens that come with bed bug control can be overwhelming for people. Treating the home, replacing belongings, and buying the necessary tools to combat bed bugs may be unaffordable. Therefore, the pest control technician must keep in mind that household items and furniture can usually be treated successfully. Property disposal should not be the first line of defense or an initial recommendation. However, recognizing the point at which a piece of furniture must be thrown away is also a key to success.