Why do bedbugs bite only at night? - briefly
Bedbugs are nocturnal feeders; they emerge after dark when humans are stationary and skin temperature rises, making it easier to locate blood vessels. Their activity aligns with the host’s sleep cycle to reduce detection and increase feeding success.
Why do bedbugs bite only at night? - in detail
Bedbugs are nocturnal hematophages, meaning they seek blood meals primarily during the dark hours. Their activity pattern is governed by an internal circadian clock that synchronizes feeding with the period when hosts are most likely to be immobile and protected by bedding. Several physiological and ecological factors reinforce this timing.
During the night, human body temperature rises slightly under blankets, producing a stronger thermal gradient that bedbugs can detect with thermoreceptors. Carbon‑dioxide output also increases as respiration slows, creating a stable plume that guides the insects toward a sleeping host. In the absence of light, visual cues are irrelevant, allowing the bugs to rely on these chemical and thermal signals without competition from diurnal predators.
The darkness reduces the chance of being disturbed. A sleeping person rarely moves, swats, or changes position, giving the bug enough time to locate a feeding site, insert its proboscis, and inject saliva containing anticoagulants and anesthetics. This process typically lasts five to ten minutes; any interruption could expose the insect to danger. Feeding in daylight would increase the probability of detection by humans or predators such as spiders and ants.
Evolutionarily, night‑time feeding conserves water. Bedbugs lose moisture through respiration and excretion; the cooler, more humid environment of a covered bed limits dehydration compared with the drier, warmer air of daytime rooms.
Key reasons for nocturnal biting:
- Internal circadian rhythm aligns activity with host rest periods.
- Enhanced thermal and CO₂ gradients under blankets facilitate host location.
- Reduced host movement minimizes disturbance and defensive responses.
- Lower predation risk in darkness.
- Favorable microclimate conserves water and prolongs survival.
These combined factors explain why bedbugs concentrate their blood‑sucking behavior on the night hours rather than throughout the day.