To find a human, a mosquito does not rely on a single sense. The carbon dioxide in our breath alerts it from a distance, then body odors and heat help it refine its trajectory. Researchers now show that thermal radiation provides it with directional information.
Every warm object emits infrared radiation that is invisible to our eyes. Human skin produces it continuously. This signal should not be confused with the warm air moving around the body: radiation can pass through the air and reach a sensor without directly transporting matter.
A mosquito in the middle of a meal.
Pixabay illustration
The researchers placed mosquitoes in a device where they could choose between different areas. The insects showed greater attraction to a surface producing infrared radiation comparable to that of human skin, especially when carbon dioxide and human odors were also present.
The effect worked at a distance where heat transported directly by the air became too weak to explain the behavior. The mosquitoes therefore had additional information before touching their target. This combination of signals may help them locate a person even in darkness.
The team then investigated the sensory mechanism involved. Structures located at the tips of the antennae absorb the radiation and warm up slightly. This change in temperature activates heat-sensitive proteins, thereby transforming infrared radiation into a nerve signal.
This discovery shows that several sensory cues work together. An isolated signal can be ambiguous: a warm source is not necessarily an animal, and an odor can remain in the air for a long time. By combining CO₂, odors, and infrared radiation, the mosquito increases its chances of identifying a nearby living target.
Understanding this mechanism could help in designing new traps that combine several signals or in disrupting thermal detection. Researchers will now need to determine how far this system remains effective in real-world environments, where wind, clothing, and other warm surfaces alter the available information.