Bed bugs (Cimex lectularius) are small parasitic insects that require blood meals to survive and reproduce. As nocturnal pests, their feeding habits are closely tied to the sleeping patterns of their human hosts. They primarily emerge during the deep sleep hours of the night. This timing allows them to feed on an immobile host, minimizing the risk of detection. Bed bugs are well-adapted to this parasitic lifestyle, often living in close proximity to where humans rest.
The Primary Nocturnal Feeding Window
Bed bugs are most active and likely to feed in the hours between midnight and 5 a.m. This window is not arbitrary; it directly corresponds to the time when the host is typically in their deepest, most sustained sleep. The insects are drawn to their host by two primary sensory cues: the carbon dioxide (CO2) exhaled during respiration and body heat.
The cyclical production of CO2 by the sleeping host acts as the main signal, prompting the bed bug to leave its hiding spot. This attraction allows them to locate a blood meal even when they are not directly on the bed. Once fed, the bed bug returns to its harborages, such as mattress seams or crevices in the headboard, to digest the meal. Adult bed bugs generally require a blood meal only once every five to ten days.
How Bed Bugs Find a Host and Feed
The process of finding a host begins with the detection of the CO2 plume, which can be sensed over short distances, and then body heat as the bug gets closer. Once on the host’s skin, the bed bug uses its specialized mouthpart, a tube-like structure called a proboscis, which consists of two sets of stylets.
One pair of stylets forms a small salivary canal that injects saliva containing both an anesthetic and an anticoagulant into the host’s skin. The anesthetic ensures the bite is generally painless during the feeding process, meaning a person rarely wakes up while being bitten. The other set of stylets forms a larger food canal used to draw the blood. A full blood meal takes between three and ten minutes, during which the bed bug may take in up to six times its body weight in blood.
When Bed Bugs Deviate From Their Schedule
While nocturnal activity is the standard behavior, bed bugs will feed outside of the midnight to 5 a.m. window if circumstances require it. The primary driver for deviation is starvation; if a bed bug has gone without a meal for an extended period, it becomes more opportunistic and will seek a host even during the day.
They also feed during daytime hours if the host is available and sedentary, such as a person working from home, taking a long nap, or being immobile due to illness. In severe, high-density infestations, competition can force some bed bugs to feed whenever possible. The host’s sustained inactivity, rather than light conditions, is the factor that makes feeding possible.