Research reveals that after they smell you, mosquitoes go for specific colors, including red and orange.

How does a mosquito locate you in the summer? A lot of research has already been done on this. And that has shown, among other things, that they rely on smells (such as the smell of sweat or CO2 in your breath. But there is more, scientists now write in the magazine Nature Communications. Because as soon as mosquitoes pick up the scent of a potential victim, they appear to fly to specific colors, such as red, orange, black and cyan (while completely ignoring colors like blue, white, green and purple). It points out that in addition to scent, mosquitoes also use color to detect us, because human skin – regardless of skin color – also emits a ‘red signal’.

Red

“One of the questions people most often ask me is, ‘What can I do to stop mosquitoes from biting me?'” said researcher Jeffrey Riffell. “I used to say that there are three things that attract mosquitoes: your breathing, your sweat and the temperature of your skin. In this study, we found another one: the color red. And that can be found not only in your clothes, but also in everyone’s skin. Skin color doesn’t matter.”

Experiments

Experiments have shown that colors (in combination with scents) do not leave the mosquito untouched. During those experiments, Riffell and colleagues placed female yellow fever mosquitoes (Aedes aegyptian) in small chambers containing colored dots. In the absence of tantalizing odors, the mosquitoes appeared to completely ignore the dots – regardless of their color. But that changed when the researchers injected some CO2 into the chambers. Then the mosquitoes suddenly flew towards the colored dot, at least: if it was red, orange, black or cyan. Green, blue and purple dots continued to ignore the mosquitoes in the presence of CO2 as well. The experiments show that after they have observed CO2, the eyes of mosquitoes develop a preference for certain wavelengths of light: the longer wavelengths, to be precise (see box).

Most people see the different wavelengths of light as different colors. For example, we see light with a wavelength of 650 nanometers as red and light with a wavelength of 450 nanometers as blue. The researchers cannot say for sure whether this also applies to mosquitoes. What they can conclude based on their experiments is that after observing CO2, the mosquitoes develop a strong preference for longer wavelengths of light, which in our perception correspond to colors such as orange and red. The color spectrum of human skin – regardless of skin color – is also dominated by those longer wavelengths of light.

Protection

The research not only provides a little more insight into how mosquitoes find us, but may also help protect us better against mosquitoes. “Filtering out those attractive colors in our skin or wearing clothes that don’t contain those colors can be one way to prevent a mosquito bite,” Riffell thinks.

Subsequent experiments also show that mosquitoes can be misled in this way. A researcher put his hand in the mosquito enclosure, after which some CO2 was injected into the enclosure. After smelling the CO2, the mosquitoes immediately set course for the hand. But when the researcher wore a green glove, the mosquitoes did not fly towards the hand after smelling CO2.

“These experiments reveal the first steps mosquitoes take to find hosts,” said Riffell. Follow-up research should show what the next step is, i.e. how mosquitoes – once closer to the host – actually manage to land on the host’s skin, based on smells and visual stimuli. Another important question to be answered in follow-up research is whether other mosquito species prefer the same colors or – for example because of a preference for hosts with a different color – prefer other shades.