As many of us know through bitter experience, humans attract mosquitoes like moths to a flame. Actually, only female mosquitoes are attracted to us since they need the proteins in blood to produce their eggs.
In this article, we’ll teach you just how female mosquitoes locate human beings. Since they only tend to come out after dark, we’ll look at how mosquitoes can see at night. Read on to find out just what attracts mosquitoes so that you can take steps to become less attractive to them!
Mosquitoes are heavily drawn to the carbon dioxide (CO2) that human beings and other animals exhale. Even among humans, increased CO2 levels are a great way to track human beings. That’s why customs officers use it to try to detect people smuggling. During disaster relief, crews use CO2 detection to find human beings buried beneath the rubble.
CO2 is also how mosquitoes detect us. They can detect it even if we are wearing heavy clothing or blankets. You see, it’s the smell of CO2 that attracts mosquitoes. Mosquitoes have highly-tuned smell (olfactory) receptors.
To prove this, one experiment placed mosquitoes in a wind tunnel. The scientists injected plumes of CO2 into this tunnel to imitate human breath. The mosquitoes followed the CO2 plume blindly, which wasn’t nearly the same response as when the background air was CO2 free.
Mosquitoes are also able to detect other signs that a human is nearby. They also use sight to detect a suitable host. The same experiment showed that after the host’s CO2 emissions attract a mosquito, that mosquito will begin to see the host once it’s within a range of around 5 to 15 meters (16 to 49 ft.). This is true even when it’s dark outside. The visual cues take over and draw the mosquito even closer to the human host. Since this happens when the mosquito is within a very close range, it means that darkness isn’t really an issue for mosquitoes.
Finally, once the mosquito is within a meter (3.2 ft.) in range, it’ll begin to sense the body heat of its host. This is what will finally allow it to latch onto its victim. Again, in the above-mentioned experiment, the researchers built a pair of glass objects and coated them in a certain chemical that enabled the scientists to heat them to any temperature. They heated one to human body temperature (around 98.6°F/37°C) while allowing the other to stay at room temperature. They placed both in the wind tunnel and observed the behavior of the mosquitoes. The mosquitoes apparently showed a strong preference for the warmer object. This was independent of whether CO2 was present.
Through these experiments, we can see how mosquitoes combine intelligence and the information gathered from all their different senses. This information helps them make decisions and find an appropriate host. Female mosquitoes first pick up on the scent of CO2, paying attention to the visual cues only after they’ve encountered odors that indicate the existence of a host nearby.
Remember, if mosquitoes had to navigate by visual cues alone, they would never find a host, especially at night. But because the visual cues only kick in at a short distance, the lack of daylight is not an issue for them. Finally, once they’re within a distance of one meter (3.2 ft.), the thermal heat radiated by the host provides the last cue the mosquito needs.
This is how mosquitoes are able to detect the presence of humans, even when it’s pitch black outside.