Bed bugs are small, parasitic insects that feed exclusively on the blood of warm-blooded hosts, primarily humans. While the common understanding is that these pests are strictly nocturnal, the reality is more nuanced. Bed bugs are generally active at night, but their behavior is adaptable and opportunistic. They prefer the dark, but they will certainly emerge during the day if conditions require it.
Why Bed Bugs Prefer the Night
Bed bugs are not strictly governed by a rigid circadian rhythm but instead respond primarily to the presence of a resting host. They are attracted to two main signals given off by sleeping humans: carbon dioxide and body heat. Exhaled breath releases carbon dioxide, which acts as a powerful beacon, drawing the insects out of their hiding spots.
The preference for nighttime feeding is largely a matter of safety and efficiency for the insect. A sleeping host is a still host, which allows the bed bug to feed for up to 10 minutes without being detected or crushed. Their peak feeding activity often occurs in the hours just before dawn, typically between 2 a.m. and 5 a.m.
When They Deviate from Nocturnal Habits
Although they are highly adapted to nighttime activity, bed bugs will readily emerge during the day in certain situations. The most common reason for a daytime sighting is extreme hunger, particularly if the host has been absent for an extended period. Bed bugs can survive for months without feeding, but a prolonged period of starvation will compel them to seek a blood meal regardless of the time or the presence of light.
Another significant factor is a shift in the host’s routine, such as for individuals who work night shifts and sleep during the day. Bed bugs are capable of adapting their feeding schedule to match their host’s resting period. Seeing live bed bugs crawling during daylight hours can also be a strong indicator of a severe, well-established infestation.
Evidence They Leave Behind
Since live bed bugs are rarely seen, identification relies heavily on recognizing the signs they leave behind near their harborages. One of the clearest indicators is the presence of fecal spots, which are small, dark stains of digested blood. These spots resemble black felt-tip marker stains on fabric and can be found in mattress seams, on bed frames, and along baseboards.
These digested blood spots are typically dark brown or black because the blood meal has been processed. They will often smear if wiped with a wet cloth, distinguishing them from simple dirt or mold. Another common sign is the appearance of shed skins, or exoskeletons. Nymphs must molt five times, requiring a blood meal between each stage, leaving behind translucent, light-brown husks.
Finally, small, rust-colored blood stains may be visible on sheets and pajamas. These stains result from a feeding bug being accidentally crushed by the host during sleep or from blood leaking from the feeding wound.
Taking Action Against an Infestation
If you confirm the presence of bed bug evidence, it is important to take immediate steps to contain the problem and prevent the pests from spreading. Avoid moving infested items, such as furniture or electronics, from the room, as this can easily spread the bugs to other parts of the home. Any bedding, clothing, or other washable fabric items in the room should be placed into sealed plastic bags and immediately taken for laundering.
Washing these items in hot water followed by a minimum of 30 minutes in a high-heat dryer will kill all stages of the bed bugs, including the eggs. While initial efforts like vacuuming seams and crevices can help remove some bugs, bed bugs are resilient and hide deep in structural voids. For a complete and lasting solution, it is recommended to contact a licensed professional pest control service.