Bedbugs (or bed bugs) are small nocturnal insects of the family Cimicidae that live by hematophagy, feeding on the blood of humans and other warm-blooded hosts.

The common bedbug (Cimex lectularius) is the best adapted to human environments. It is found in temperate climates throughout the world and has been known since ancient times.

Other species include Cimex hemipterus, found in tropical regions (including Florida), which also infests poultry and bats, and Leptocimex boueti, found in the tropics of West Africa and South America, which infests bats and humans. Cimex pilosellus and C. pipistrella primarily infest bats, while Haematosiphon inodora, a species of North America, primarily infests poultry.

Oeciacus, while not strictly a bedbug, is a closely related genus primarily affecting birds.

PHYSICAL CHARACTERISTICS
Adult bedbugs are reddish brown, flattened, oval, and wingless, with microscopic hairs that give them a banded appearance. A common misconception is that they are not visible to the naked eye, but adults grow to 4 to 5 mm (one-eighth to three-sixteenths of an inch) in length and do not move quickly enough to escape the notice of an attentive observer. Newly hatched nymphs are translucent and lighter in color and continue to become browner and molt as they reach maturity. When it comes to size, they are often compared to lentils or appleseeds.

FEEDING HABITS
Bedbugs are generally active only at night, with a peak attack period about an hour before dawn, though given the opportunity, they may attempt to feed at other times of day. Attracted by warmth and the presence of carbon dioxide, the bug pierces the skin of its host with two hollow tubes. With one tube it injects its saliva, which contains anticoagulants and anesthetics, while with the other it withdraws the blood of its host. After feeding for about five minutes, the bug returns to its hiding place. The bites cannot usually be felt until some minutes or hours later, as a dermatological reaction to the injected agents. Although bedbugs can live for up to 18 months without feeding, they typically seek blood every five to ten days.

Bedbugs are often erroneously associated with filth. They are attracted by exhaled carbon dioxide, not by dirt, and they feed on blood, not waste. The cleanliness of their environments has no effect on bedbugs.

While bedbugs have been known to harbor pathogens in their bodies, including plague and hepatitis B, they have not been linked to the transmission of any disease and are not regarded as a medical threat. Some individuals, however, can get skin infections and scars from scratching bites. While bedbugs are not regarded as a vector of transmissible diseases, they are a serious stressor and will create a lot of alarm and distress. With some individuals, it may precipitate mild to moderate cases of delusory parasitosis.

METHOD OF INITIAL INFESTATION
There are several means by which dwellings can become infested with bedbugs. People can often acquire bedbugs at hotels, motels, and bed-and-breakfasts, thanks to increased domestic and international tourism, and bring them back to their primary domiciles in their luggage. They also can pick them up by inadvertently bringing infested furniture or used clothing to their household either via purchase or "dumpster diving". If someone is in a place that is severely infested, bedbugs may actually crawl onto and be carried by people's clothing, although this is atypical behavior — except in the case of severe infestations, bedbugs are not usually carried from place to place by people on clothing they are currently wearing. Finally, bedbugs may travel between dwellings (such as condominiums and apartment buildings, after being originally brought into the building by one of the above routes. This spread between units is dependent in part on the degree of infestation (if the infestation has not been reported), on the structure of the building (less likely if the partition walls are concrete), and whether or not infested items on their way towards disposal are dragged through common areas, shedding bedbugs and eggs on their way (that then find their way into other units).

COMMON LOCATION OF INFESTATION
Bedbugs are very flat, allowing them to hide in tiny crevices. A crack wide enough to fit the edge of a credit card can harbor bedbugs. In the daytime, they tend to stay out of the light, hidden in such places as mattress seams, mattress interiors, bed frames, nearby furniture, carpeting, baseboards, or bedroom clutter. Although bedbugs can hide individually, they are social creatures and more often will congregate in groups. Bedbugs are capable of travelling as far as 100 feet to feed, but generally camp in the bedrooms of their hosts, feeding every five to 10 days, and occasionally migrating to a nearby bedroom.

SIZE OF INFESTATIONS
Some pest control professionals have deemed light infestations to be anything below 200 bedbugs in a residence, medium infestations to be in the range of 200–300 bedbugs in a residence, and severe infestations to be as bad as 2,000–3,000 bedbugs in a single residence.

DETECTION OF INFESTATIONS
Bedbugs can be detected often by looking for black tracks on bedding, which are the bedbugs' fecal stains. These stains are most visible on light-colored bedding.

Bedbugs cannot "snip" thread as purported by some as they do not have chewing or "biting" mouth parts. A bedbug "bite" is in fact, a piercing of the skin by their specialized mouthparts. They may however travel in the linen and settle into the open weave, which will appear as a gray spindle a centimeter long and a thread wide, with a dark speck in the middle.

Occasionally an engorged bedbug is inadvertently killed or disgorged by incidental crushing, resulting in a visible smear of blood. Crushing them will produce a unique sickly sweet pheremone scent, which can also be detected in the ambient air in a severe infestation.

Though bedbug bites can occur singly, they often follow a distinctive pattern of a linear group of three bites, sometimes macabrely referred to as "breakfast, lunch and dinner". The effect of these bites on humans varies from person to person, but often cause welts and swelling that are more itchy and longer-lasting than mosquito bites. Some people, however, have little or no reaction to bedbug bites. Those whose bodies do not initially react may subsequently develop symptoms, however, due to an allergic reaction caused by the development of antigen. A technique for "catching" (detecting) bedbugs is to have a light source accessible from bed and to turn it on at about an hour before dawn, which is usually the time when bedbugs are most active. A flashlight is recommended instead of room lights, as the act of getting out of bed will cause any bedbugs present to scatter. Bedbugs can also sometimes be viewed during the day.

Some individuals have used glue traps placed in strategic areas around their domicile (sometimes used in conjunction with heating pads, or balloons filled with exhaled breath, thus offering the carbon dioxide that bedbugs look for) in order to attract and thus detect bedbug infestations. There are also commercial traps like "flea" traps whose effectiveness is really questionable except perhaps as a means of detection, but traps will certainly not work to control an infestation.

Veterinarians may mistake bedbugs' leavings on a pet's fur as "flea dirt".

The above having been said, bedbugs are known for being elusive, transient and nocturnal. For many, the only way to detect and identify with certainty an infestation is to contact a pest control professional.

LIVING WITH INFESTATION
If it is necessary to live with bedbugs in the short term, it is possible to create makeshift temporary barriers around a bed. Because bedbugs cannot fly or jump, an elevated bed can be protected by applying double-sided sticky tape (carpet tape) or petroleum jelly around each leg, or by keeping each leg on a plastic furniture block in a tray of water. A bed frame can be effectively ridded of adult bedbugs and eggs by use of steam. Small steam cleaners are available and are very effective for this local treatment. A suspect mattress can be protected by wrapping it in a painter's disposable plastic dropcloth, neatly sealing shut all the seams with packing tape, and putting it on a protected bed after a final visual inspection. Bedding can be sanitized by a 120° F (49° C) laundry dryer. Once sanitized, bedding should not be allowed to drape to the floor. An effective way to quarantine a protected bed is to store sanitized sleeping clothes in the bed during the day, and bathing before entering the bed.

Vermin and pets may complicate a barrier strategy. Bedbugs prefer human hosts, but will resort to other warm-blooded hosts if humans are not available, and some species can live up to eighteen months without feeding at all. A co-infestation of mice can provide an auxiliary food source to keep bedbugs established for longer. Likewise, a house cat or human guest might easily defeat a barrier by sitting on a protected bed. Such considerations should be part of any barrier strategy.