How Mosquitoes Find You: Smell, Sight and Temperature

How do mosquitoes find us before they bite us? Let me count the ways. One, they smell us, or more specifically, they smell the carbon dioxide that is exhaled every time we breathe out. Two, they also see us, or at least they use their eyes to detect dark objects, which are particularly attractive to mosquitoes who have already detected carbon dioxide. And three, they sense our body heat and move in our direction. How do we know this? Because researchers at Caltech conducted several experiments, exposing mosquitoes to carbon dioxide plumes, dark objects, and objects that were heated to roughly our body temperature. The interesting part? All mosquitoes were attracted by carbon dioxide, and mosquitoes under the influence of carbon dioxide showed a stronger preference for dark objects than mosquitoes that had not been exposed to carbon dioxide. The temperature attraction? That worked with or without carbon dioxide, but it only worked when the mosquitoes were very close to their dinner. A Caltech news release reports that the researchers hypothesize that the hunt works like this: From 10 to 50 meters away, a mosquito smells a host’s CO2 plume. As it flies closer—to within 5 to 15 meters—it begins to see the host. Then, guided by visual cues that draw it even closer, the mosquito can sense the host’s body heat. This occurs at a distance of less than a meter.