The common bed bug, Cimex lectularius, is a parasitic insect that feeds exclusively on blood, primarily from humans. Although they rely on people for nourishment, they do not live on a person; they only travel on them for transport or feed briefly. Bed bugs are classified as nest-dwelling ectoparasites, meaning they prefer hidden locations near their host rather than residing directly on the body like lice or fleas. This distinction explains their behavior and life cycle.
Bed Bug Biology and Host Preference
Bed bugs are not adapted to live permanently on a human host due to several biological factors. Their bodies are dorsoventrally flattened, which allows them to easily hide in narrow cracks and crevices. However, this shape is not suitable for clinging to human hair or skin. Unlike true ectoparasites, bed bugs lack the specialized anatomy, such as strong claws or mouthparts, that would allow them to remain fixed in human hair or fur.
The insects are nocturnal feeders, only making contact with a host for a brief period to consume a blood meal, typically taking three to twelve minutes. Once engorged, their body size triples, making them conspicuous and incapable of remaining discreetly on a host. After feeding, they immediately retreat to a secluded harborage to digest the blood and lay eggs.
Temporary Transport and Hitchhiking
The primary method of bed bug spread is passive movement, often called “hitchhiking,” which is how they travel on people’s belongings. When a person is near an infested area, such as a hotel room or public transport, a bed bug may crawl onto an item being carried or worn. They are attracted to the carbon dioxide and warmth associated with a host, driving them to seek out items that will transport them to a new location.
The bugs do not typically cling to exposed skin or hair but rather hide in the seams and folds of clothing, luggage, backpacks, and purses. They are capable of squeezing their thin bodies into the smallest crevices of personal items. This transport phase is temporary, as the bed bug seeks a new, permanent harborage near a new host.
Finding the True Hiding Places
When not feeding or traveling, bed bugs establish their homes, known as harborages, in dark, protected areas. These nesting sites are nearly always found in close proximity to a sleeping host, usually within 5 to 20 feet of the bed. Common locations include the piping, seams, and tags of mattresses and box springs, as well as cracks in the bed frame and headboard.
As an infestation grows, the bugs will spread to nearby furniture like nightstands and couches, or even behind loose wallpaper and in electrical outlets. Physical evidence of these harborages includes rusty or reddish-brown fecal spots, shed pale-yellow nymph skins, and tiny, white eggs. These cryptic, undisturbed locations provide shelter for the bed bug to digest its meal, mate, and lay eggs.