Mosquitoes prefer to bite humans wearing red, orange or black clothing

SEATTLE (StudyFinds.org) – Pesky mosquitoes are more attracted to people wearing red, orange or black clothing, scientists say. If you’re looking to ward them off, your outfit better have a lot of green, purple, blue, or white. You will also need to cover up, as any color of human skin will appear red to them.

The results of the University of Washington study could help us avoid annoying parasites and their itchy bites. Not to mention that they can additionally help avoid potentially contracting the Zika or West Nile viruses, as well as other mosquito-borne diseases.

Scientists say insects fly to specific colors once they smell a plume of CO2 from human breath. Once they catch a puff, they zero in on particular hues that grab their attention. Avoiding the bloodsuckers this spring and summer may depend on choosing the right clothes to cover your skin.

“Mosquitoes seem to use smells to help them distinguish what’s nearby, such as a host to bite,” says study lead author Jeffrey Riffell, a professor of biology at the university, in a statement. “When smelling specific compounds, like CO2 from our breath, this scent stimulates the eyes to seek out specific colors and other visual patterns, which are associated with a potential host, and to steer towards them.”

Colorful discoveries may lead to better mosquito repellents

The findings shed some light on why mosquitoes attack some people and leave others alone. In addition to red, orange, and black, they also like other colors like aqua and cyan. Human skin, regardless of its overall pigmentation, emits a strong red-orange “signal” to insect eyes. His sense of smell, or olfaction, influences how he responds to visual cues.

Knowing what attracts hungry pests also opens the door to better development. mosquito repellents, traps and other methods to keep them at bay. “One of the most common questions I get asked is, ‘What can I do to keep mosquitoes from biting me? says Riffell. “I used to say that there are three main signals that attract mosquitoes: your breath, your sweat and your skin temperature. In this study, we found a fourth clue: the color red, which is found not only on your clothes, but also on everyone’s skin. No matter your skin tone, we all have a strong red signature. Filtering out these attractive colors on our skin, or wearing clothes that avoid these colors, could be another way to keep a mosquito from biting.

For the study, Riffell and her team tracked the behavior of women Aedes aegypti mosquitoes in a test chamber when exposed to visual and olfactory cues. Like all mosquito species, only females drink blood. Bites of A. aegypti can transmit dengue fever, yellow fever, chikungunya and Zika.

Specific smells were sprayed. Patterns such as a colored dot or a tasty human hand were also featured. Without any scent stimulus, the insects largely ignored the mark at the bottom of the chamber, regardless of color. After a CO2 spritz, they continued not to care if it was green, blue or purple.

But they headed straight for the dot when it was red, orange, black, or cyan.

It’s mostly about your smell, but colors can keep pests away

Humans cannot smell CO2, which we and other animals exhale with each breath. Mosquitoes can. Previous research has shown that it stimulates the activity of females, causing them to explore the surrounding space in search of a host. The latest study reveals that after sniffing the gas, their eyes prefer certain wavelengths of the visual spectrum.

This is similar to what might happen when humans smell something good.

“Imagine you’re on a sidewalk and you smell pie crust and cinnamon. It’s probably a sign that there’s a bakery nearby, and you might start looking for it,” says Riffell. “Here we started to learn what visuals mosquitoes look for after smelling their own version of a bakery.”

Most humans have “true color” vision. We see different wavelengths of light as distinct colors. For example, 650 nanometers appear in red while 450 wavelengths appear in blue. Researchers don’t know if mosquitoes perceive colors the same way.

But most of the ones that mosquitoes prefer – orange, red and black – correspond to longer wavelengths of light. Human skin also emits a long wavelength signal in the red-orange range.

When the tests were repeated with human skin tone pigmentation charts, or a researcher’s bare hand, mosquitoes again flew to the visual stimulus only after the introduction of CO2. If the filters suppressed long wavelength signals or if a green colored glove was worn, they did not.

Mosquitoes with a mutation needed to sense CO2 no longer showed color preference. Another strain of mutant mosquitoes, with a vision-related change so they couldn’t “see” long wavelengths of light, were more colorblind in the presence of CO2.

“These experiments expose the first steps that mosquitoes use to find hosts,” says Riffell.

Further research is needed to determine how other visual and olfactory signals, such as skin secretions, help mosquitoes target potential hosts at close range. Other mosquito species may also have different color preferences, depending on their preferred host species. But the new findings add a new colorful layer to mosquito control.

The study is published in the journal Communication Nature.

South West News Service writer Mark Waghorn contributed to this report.

Elizabeth J. Harless