As many of us know by bitter experience, mosquitoes are drawn to humans like a moth to a flame. Actually, however, it is only the females of the mosquitoes that are attracted to us – this is because they require the proteins contained in human blood to create and nourish their eggs. In this article, we are here to teach you just HOW female mosquitoes locate human beings, seeing as they only tend to come out after dark. Read on to find out just what attracts mosquitoes to us!
Carbon dioxide: mosquitoes are heavily drawn to the carbon dioxide that human beings as well as other animals exhale. Actually, even amongst humans, enhanced carbon dioxide levels are a great clue for tracking down human beings – this is why it used by customs officers trying to detect people smuggling, as well as in disaster relief where human beings are buried beneath rubble. Carbon dioxide is also how mosquitoes detect us – they can ‘smell’ it even when we are wrapped beneath heavy clothing and sheets. You see, it is the ODOR of carbon dioxide that mosquitoes are attracted to, and mosquitoes have highly attuned smell (olfactory) receptors. One experiment showed that when mosquitoes were placed into a wind tunnel and carbon dioxide plumes were also and subsequently injected into this tunnel (imitating the breath of a human being), the mosquitoes followed it blindly – not nearly the same response was seen when the background air was free of carbon dioxide.
Vision: mosquitoes are also able to detect other signals that a human being is in nearby proximity. They utilize their VISION to detect a suitable host as well. The same experiment showed that once a mosquito has been drawn to a host by its carbon dioxide emissions, it then, once it is within a range of 5 to about 15 meters, starts to SEE the host. This is true even when it is dark and in the dead of night. The visual cues then take over, and draw it even closer to the human host (remember they can only see the host once they are within a very close range, so the fact that it is dark is not really an issue).
Thermal attraction: Finally, once the mosquito is within a range of less than a meter, it begins to sense the body heat of the human host. This is what finally allows it to latch onto its host.Again, in the above mentioned experiment, the researchers built a pair of glass objects that were coated in a certain chemical that enabled them to heat it up to any temperature. They heated one to approximate human body temperature (about 37 degrees Celsius), whilst allowing the other to stay at room temperature. They then placed both in the wind tunnel, and observed the behavior of the mosquitoes. Apparently, the mosquitoes showed a strong preference for the object that was warmer – NOT dependent on the whether or not carbon dioxide was present.
Through these experiments, we can see how mosquitoes combine intelligence and information from all the different senses in order to make decisions and find an appropriate host. Female mosquitoes first pick up on the scent of carbon dioxide, THEN pay attention to the visual cues only AFTER they’ve been drawn in by odors that indicate the existence of a nearby host. Remember, if they were forced to navigate by visual cues alone, they would never find a host, because they operate 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, and once they are within a distance of one meter, the thermal heat radiated by the host provides the last cue that draws the mosquitoes in. That, then, is how mosquitoes are able to detect human presence, EVEN WHEN it is pitch black outside.