Carbon Dioxide

(© Dennis Kunkel Microscopy, Inc./Visuals Unlimited/Corbis)

One of the key ways mosquitoes locate their targets is by smelling the carbon dioxide emitted in their breath—they use an organ called a maxillary palp to do this, and can detect carbon dioxide from as far as 164 feet away. As a result, people who simply exhale more of the gas over time—generally, larger people—have been shown to attract more mosquitoes than others. This is one of the reasons why children get bit less often than adults, on the whole.