Mosquitoes are incredibly perceptive insects that use a variety of senses to locate and feed on their prey. Their ability to detect subtle cues from humans and animals allows them to exploit opportunities to obtain blood meals. But do mosquitoes specifically know when you are asleep? Let’s explore the evidence.
How mosquitoes detect humans
Mosquitoes rely primarily on their sense of smell to detect potential hosts to bite. They have receptors on their antennae that can pick up chemical cues and odors emitted from the body. These include:
- Carbon dioxide – Humans exhale this gas when breathing. Mosquitoes can detect CO2 from over 50 feet away.
- Lactic acid – A compound released through sweat. Mosquitoes are especially attracted to the bacteria on human skin that produce lactic acid.
- Body odor – Bacteria and microbes living on the skin produce distinctive odors that signal a human presence.
When a mosquito senses these attractive chemical cues, it will fly upwind to investigate a potential host. It can follow odor plumes just like we might follow the scent of something appealing.
How mosquitoes zero in
Once a mosquito gets relatively close to a person, it switches to visual and thermal cues to pinpoint an ideal biting spot. Mosquitoes typically bite around ankles and knees, where blood vessels are most accessible. They use their vision to identify dark colors and contrasting patterns on the skin associated with blood vessels. As they approach even closer, mosquitoes rely on thermoreceptors to sense the warmer areas of the body that signal an active blood supply.
Are mosquitoes attracted to specific times of day?
Mosquitoes that feed at night, like the common Culex species, use circadian rhythms to guide their behaviors. They are active and seek hosts more aggressively at dusk and dawn. During the day, they rest in cool, shady areas. However, they can still take blood meals if presented with the opportunity.
Daytime biters like Aedes mosquitoes are more flexible in their feeding times. Still, they tend to be most active in the early morning and late afternoon. Mosquitoes generally avoid the heat of midday.
Do mosquitoes specifically target sleeping humans?
It is true that many mosquito species preferentially bite at night when humans are sleeping. But mosquitoes do not know whether you are asleep or awake per se. However, a sleeping human does present some unique cues that make for an attractive target:
- Minimal movement – Mosquitoes are sensitive to vibrations and avoid active, moving hosts. A sleeping human stays perfectly still.
- High CO2 – Breathing slows during sleep, resulting in greater concentration of exhaled CO2 that lures mosquitoes.
- Warmth – At night, a human body heat signature contrasts strongly with the cool surroundings.
- Ease of access – With hands and feet often exposed from blankets, mosquitoes have clear biting sites.
So while mosquitoes do not intentionally identify a sleeping human, the conditions of sleep coincide with the optimal cues mosquitoes use to select their prey.
Studies on mosquito biting and sleep
Controlled research provides some additional insights into how mosquito feeding activity is linked to human sleep patterns:
- One study found Aedes mosquitoes were 4-5 times more likely to feed on a sleeping person compared to someone awake and moving minimally.
- Data shows higher mosquito bite rates overnight compared to the evening or morning when people are more often awake.
- Mosquitoes respond to melatonin levels, which rise at night and induce sleep, suggesting they may associate this hormone with vulnerability.
However, other studies show mosquitoes will readily bite sleeping and awake humans in the daytime. So while mosquitoes do selectively target sleeping humans at night, they are still opportunistic feeders that will bite an accessible host regardless of sleep state given the chance.
| Study | Key Finding |
|---|---|
| Ribeiro et al. (1985) | Aedes mosquitoes 4-5x more likely to bite sleeping human than one minimally active while awake |
| Ferreira de Lima et al. (2013) | 83% of Anopheles bites occurred when hosts were asleep from 10 pm – 4 am |
| Fornadel et al. (2011) | No increased attraction to sleeping humans during daytime |
How to avoid mosquito bites while sleeping
If you want to thwart those nighttime mosquito ambushes, here are some effective tactics:
- Use bed nets – Mosquito netting provides a protective barrier around your bed.
- Apply repellents – DEET or picaridin-based repellents can be applied before bed for all-night protection.
- Eliminate standing water – Drain any sources of standing water around the home to reduce mosquito breeding areas.
- Use air conditioning – Cooler indoor temperatures make you less noticeable to mosquitoes.
- Wear long sleeves & pants – Covering up limits exposed skin that mosquitoes can bite.
- Try fans – Strong air currents from fans disorient and deter mosquitoes.
- Remove attractants – Avoid scented products and eating bananas/drinking beer before bed, as their odors lure mosquitoes.
Conclusion
Mosquitoes do not have a way to actively detect whether a human is awake or asleep. However, the physical and chemical changes that occur when a person is sleeping just happen to generate the optimal signals that attract mosquitoes and enable them to hone in easily. While mosquitoes will readily bite exposed skin any time of day, sleeping humans are the perfect stationary target emitting inviting sensory cues into the night. With some simple measures to block these signals, you can gain the upper hand over these wily nighttime biters.