Bedbugs are small parasitic insects that feed exclusively on blood. These pests are notorious for remaining hidden, only emerging to seek a blood meal from a sleeping host. Understanding the timing and mechanisms of their activity is the first step toward detection and control.
The Bedbug Activity Cycle
Bedbugs are widely described as nocturnal, meaning they are primarily active during the night. This behavior is a survival strategy, allowing them to feed on a host that is immobile and unlikely to detect their presence. Their peak feeding period typically occurs between 2 a.m. and 5 a.m., when a human host is usually in the deepest stages of sleep.
While nocturnal is the common description, their activity is not strictly tied to the absence of sunlight. The insects are more attuned to the host’s state of rest than to the clock itself. If a person consistently sleeps during the day, bedbugs will adjust their routine to become active during those daylight hours.
The sight of a live bedbug during the day is rare and often signals a severe situation. Extreme hunger, a crowded harborage, or a disturbed hiding spot can force a bedbug to move in the daytime. They are naturally averse to light and prefer to operate under the cover of darkness.
How Bedbugs Sense a Sleeping Host
Bedbugs possess specialized senses that allow them to locate a host without relying on vision. They are primarily attracted by the carbon dioxide (CO2) that humans exhale, which signals that a host is nearby and inactive. They can detect this CO2 trail from about three feet away.
Once within range, they use thermal receptors to sense the subtle difference between the host’s body temperature and the ambient room temperature. This body heat provides the final, precise target for feeding. Their antennae contain both olfactory (smell) and gustatory (taste) sensory functions that aid in this process.
The combination of darkness, elevated CO2, and a distinct heat signature cues the insects to leave their shelter. The hairs on their legs also serve a sensory function, helping them navigate and locate their target. This biological radar system makes their feeding time reliably timed to a person’s deepest sleep.
Where Bedbugs Spend the Daylight Hours
During the day, bedbugs retreat to secure locations known as harborages, seeking dark, secluded spaces close to their host. Due to their flattened bodies, they can squeeze into cracks and crevices as thin as a credit card. These shelters are typically within a short crawling distance of the bed, often three to six feet away.
The most common hiding spots are found directly on or immediately surrounding the bed structure. This includes the seams, tufts, and folds of the mattress and box spring, as well as the joints and screw holes of the bed frame and headboard. They prefer materials like wood and fabric that offer numerous tiny gaps for concealment.
Beyond the bed, they may hide behind peeling wallpaper, in electrical outlets, or within the joints of nearby furniture like nightstands and dressers. Detecting them in these areas is difficult, but signs like tiny black fecal spots, shed skins, and blood smears indicate a nearby harborage. If an infestation is severe, they will spread to baseboards, picture frames, and even electronics.