For years, scientists believed that mosquitoes were able to find us by zeroing in on the carbon dioxide in our breath. However, new research has shown that it is a combination of CO2, human odor and heat that lead the pesky insects to us.
A team of researchers led by Conor McMeniman at the Laboratory of Neurogenetics and Behavior, Rockefeller University, New York, were able to mutate a gene in the CO2 receptor in Aedes aegypti, a common type of mosquito which spreads yellow fever. The mutated insects were not able to detect or respond to CO2.
But they found humans to bite anyway. For mosquitoes, access to blood is crucial. It is only the female mosquitoes that bite, and the blood they collect is necessary to produce fertile eggs.
It turns out that when CO2 detection was taken away, the mosquito’s response to heat and odor cues where heightened. While attraction to live hosts was diminished, it didn’t stop them from finding people.
“Because blood feeding is such an important behavior for the mosquito, evolution has built in these mechanisms that ensure the most efficient use of the insect’s energy,” said McMeniman. “There are a lot of things that give off heat, and it would be a waste for a mosquito to try to bite all of them. But with several factors present, the insect can increase her chances of a fruitful bite in a cluttered sensory environment.”
The long-term goal of the research is to help design chemical repellents to block host-seeking behavior in mosquitoes that spread malaria.
Interestingly, loss of CO2 detection did make them less likely to find a mouse in the same test environment as the humans. The researchers concluded that without carbon dioxide as a cue, the effect of odor and heat are diminished as the insect moves farther away from the host.
The findings are in a paper titled, "Multimodal Integration of Carbon Dioxide and Other Sensory Cues Drives Mosquito Attraction to Humans."
How do mosquitoes know to bite humans?
Mosquitoes use a variety of sensory cues to locate their human hosts, including:
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Carbon dioxide: Mosquitoes are attracted to the carbon dioxide we exhale, which they detect using special receptors called maxillary palp receptors.
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Body odor: Mosquitoes are also attracted to the body odor we emit, which is a mixture of chemicals produced by our skin bacteria and sweat glands.
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Heat: Mosquitoes are also able to sense the heat we radiate, particularly from our head and torso.
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Movement: Mosquitoes can detect movement from a distance, and are attracted to people who are moving around.
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Clothing color: Mosquitoes are more attracted to people wearing darker colored clothing.
How do you keep mosquitoes from biting you?
Here are some tips to help keep mosquitoes from biting you:
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Use insect repellent: Applying insect repellent to exposed skin can help keep mosquitoes away. Look for a repellent that contains DEET, picaridin, IR3535, or oil of lemon eucalyptus.
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Wear protective clothing: Wearing long sleeves and pants can help reduce the amount of exposed skin that mosquitoes can bite. It is also a good idea to wear light-colored clothing, which is less attractive to mosquitoes.
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Eliminate standing water: Mosquitoes lay their eggs in standing water, so eliminating sources of standing water around your home, such as birdbaths, flowerpots, and clogged gutters, can help reduce the number of mosquitoes in your area.
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Use mosquito netting: If you are camping or sleeping outside, using mosquito netting over your bed can help keep mosquitoes away while you sleep.
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Stay indoors during peak mosquito hours: Mosquitoes are most active during dawn and dusk, so avoiding outdoor activities during these times can help reduce your chances of being bitten.
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Use fans: Mosquitoes are weak fliers, so using a fan can help keep them away from your skin. Additionally, fans help to dissipate carbon dioxide, which can confuse and disorient mosquitoes.
By following these tips, you can help reduce your chances of being bitten by mosquitoes and potentially contracting mosquito-borne illnesses.