The perception that mosquitoes locate human hosts solely through carbon dioxide (CO2) exhalation and body heat is incomplete. Scientific investigations have clarified that these insects rely heavily on visual cues, particularly color, to finalize their approach. The detection of a host’s odor acts as a trigger, activating the mosquito’s visual system to scan for specific wavelengths of light. This two-part sensory process means the colors worn by a person can influence whether they are targeted.
How Mosquitoes See the World
The mosquito’s search for a blood meal begins with olfaction, or the sense of smell, as they can detect the CO2 plume from human breath from a distance of up to 30 feet. This initial chemical signal does not lead them directly to a host but instead primes their visual system for tracking. The detection of CO2 essentially flips a switch, prompting the mosquito to begin looking for a visual object in the immediate vicinity.
Mosquitoes are primarily sensitive to light in the long-wavelength range of the visible spectrum, which corresponds to the red and orange hues that humans perceive. Their visual apparatus is less responsive to shorter-wavelength light, which includes colors like green, blue, and purple. This sensitivity profile allows them to identify and track objects that contrast sharply with the background once they have been guided into the general area by the CO2 plume.
Colors That Actively Attract Mosquitoes
Once a mosquito’s visual system is activated by CO2, it is drawn to objects reflecting long-wavelength light, including red, orange, and black. The attraction to red and orange is strong because human skin, regardless of pigmentation, emits a long-wavelength signal in this range. This inherent red-orange signature is what the mosquito’s visual system interprets as a potential blood meal.
The color red, which typically reflects light around 650 nanometers, mimics the visual signal provided by the presence of blood vessels close to the skin’s surface. Filtering out this specific red-orange wavelength from the visual stimulus has been shown to eliminate the attraction response in laboratory settings. Similarly, mosquitoes are drawn to black and other very dark colors, like dark blue or cyan, because they create a high-contrast object against the horizon or a lighter background.
Dark colors also absorb heat, which complements the mosquito’s ability to sense body temperature as it approaches its target. When a dark object is viewed after the CO2 trigger, it represents a large, warm, high-contrast target that is easily distinguishable from the environment. This combination of long-wavelength reflection and high contrast provides a clear pathway for the insect to home in on its host.
Colors Mosquitoes Ignore or Avoid
The most effective colors for avoiding a mosquito’s visual detection are those that fall into the short-wavelength end of the spectrum, such as green, light blue, and purple, in addition to white. These colors do not stimulate the mosquito’s visual receptors in the same way that red and orange do, meaning they fail to trigger the final visual tracking phase of the hunt. In controlled experiments, mosquitoes that detected CO2 flew toward red or orange dots but completely ignored dots that were green or purple.
White is a useful color because it reflects all wavelengths of light and does not provide the high-contrast silhouette that a dark color does. Light colors also reflect heat, which minimizes the thermal signature the mosquito uses to pinpoint a landing spot at close range. Green and violet are the least attractive, with violet having the shortest wavelength on the visible spectrum and eliciting the lowest attraction response of all colors tested.