Mosquitoes are indeed attracted to sugar, but this fact is often misunderstood. The attraction is not to the sugar within a person’s bloodstream, but to sugar as a fundamental energy source found in nature. For mosquitoes, sugar is fuel. This distinction is central to understanding why these insects bite humans, a behavior driven by an entirely different set of needs.
Mosquitoes’ Need for Sugar
All mosquitoes, both male and female, require sugar to live. Their primary food source for energy is not blood, but the nectar they collect from flowers and sweet juices from other plants. These plant-based sugars provide the carbohydrates to power their flight and sustain their daily metabolic activities. This is why mosquito populations are often concentrated in areas with abundant flowering vegetation.
The need for sugar is constant and more frequent than the need for blood. It is the fuel that keeps the mosquito alive and active, allowing it to fly, mate, and, in the case of females, search for a host. This dietary habit is so ingrained that scientists have developed baits that use fruit scents to lure mosquitoes to a lethal, sugar-based meal. Without access to these sugars, a mosquito cannot survive for long.
The Role of a Blood Meal
The act of biting a human or another animal is exclusive to female mosquitoes and is separate from their need for energy. While plant nectar provides fuel for flight, a blood meal provides the building blocks for reproduction. Blood is a source of proteins and lipids, which are compounds necessary for the development of eggs. A female mosquito cannot produce viable eggs without the nutrients from blood.
After consuming a blood meal, the female mosquito will rest for several days while her body digests the blood and forms the eggs. Once the eggs are ready, she will lay them in a suitable location, often in or near water. This reproductive cycle explains why female mosquitoes are persistent in their search for a host. The sugar they get from a blood meal is incidental to their primary goal.
What Actually Attracts Mosquitoes to People
Mosquitoes do not find their human targets by sensing the sugar content in their blood. Instead, they rely on a combination of sensory cues to locate a potential host from a distance. The primary long-range attractant is the carbon dioxide (CO2) that humans and other animals exhale. A mosquito can detect plumes of CO2 from many meters away, following the concentration gradient toward its source.
As a mosquito gets closer, a different set of signals takes over. Body heat, or thermal cues, helps the insect pinpoint a warm-blooded target. At very close range, chemical compounds in a person’s sweat and on their skin become attractants. These include substances like lactic acid, ammonia, and other organic acids that create a unique scent profile. It is this blend of CO2, heat, and body odor—not the sweetness of blood—that makes a person a target.