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They discover that the red color attracts more mosquitoes

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Mosquitoes are attracted to red and therefore bite more those who see dressed in this color. This is the conclusion of recent scientific research, which has provided hitherto unknown clues to combat these annoying insects. Avoiding clothing in this shade can help keep mosquitoes away.

Research led by scientists at the University of Washington indicates that a species of common mosquito, after detecting the CO2 exhaled by humans when breathing, flies towards specific ‘colors’, including red, orange, black and cyan . Mosquitoes ignore other colors, such as green, purple, blue, and white.

The researchers believe these findings help explain how mosquitoes find hosts, since human skin, regardless of its pigmentation, also emits a strong red-orange “signal” to your eyes.

In reality, it is as if these insects ‘smell’ the colors that seem most promising to them. “Mosquitoes seem to use odors to help them distinguish what’s nearby, such as a biting host,” said senior author Jeffrey Riffell, a UW biology professor.

“When they smell specific compounds, like the CO2 in our breath, that smell stimulates their eyes to look for specific colors. and other visual patterns, which are associated with and directed at a potential host,” he explains.

The results, which have just been published in Nature CommunicationsThey reveal how the mosquito’s sense of smell influences its visual abilities. Knowing which colors attract hungry mosquitoes and which ones don’t can help you design better repellants, traps, and other methods to keep these pesky bugs at bay.

Our skin is also red for mosquitoes

“One of the most common questions I get asked is ‘What can I do to keep mosquitoes from biting me?'” Riffell said. “I used to say that there are three main signals that attract mosquitoes: your breath, your sweat, and the temperature of your skin. In this study, we have found a fourth sign: the color red, which can not only be found on your clothes, but also on everyone’s skin“, he claimed.

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“No matter your skin tone, we all give off a strong red signature. Filter those attractive colors into our skin, or wearing clothes that avoid those colors could be another way to prevent mosquito bites“, he added.

In their experiments, the team tracked the behavior of female yellow fever mosquitoes, Aedes aegypti, when presented with different types of visual and olfactory cues. Like all species of mosquitoes, only the females drink blood and the bites of A. aegypti They can transmit dengue, yellow fever, chikungunya and zika.

The researchers investigated individual mosquitoes enclosed in small containerswhich sprayed specific odors and exhibited different types of visual patterns, such as a colored dot or a tasty human hand.

Without any odor stimuli, the mosquitoes largely ignored the color point, regardless of color. After a CO2 spray into the chamber, the mosquitoes continued to ignore the dot, whether it was green, blue, or purple. But if the dot was red, orange, black, or cyan, the mosquitoes would fly to it.

Tras smell CO2, they prefer red

Humans cannot smell CO2, which is the gas that we and other animals exhale with each breath. But mosquitoes can smell it. Previous research by Riffell’s team and other groups showed that smelling CO2 increases the activity level of female mosquitoes: They search the space around them, presumably looking for a host. Experiments with colored dots revealed that after smelling the CO2, the eyes of these mosquitoes prefer certain wavelengths in the visual spectrum.

It’s similar, the researchers note, to what might happen when humans smell something good. “Imagine you’re on a sidewalk and you smell a delicious lemon cake. That’s probably a sign that there’s a bakery nearby, and you might start looking for it. Here, we begin to learn what visuals mosquitoes look for after smelling their own version of a bakery,” he explained.

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Most humans have “true color” vision: we see different wavelengths of light as distinct colors: 650 nanometers show up as red, while wavelengths of 450 nanometers show up as blue, for example.

Researchers don’t know if mosquitoes perceive colors the same way our eyes do. But most of the colors that mosquitoes prefer after smelling CO2 (orange, red, and black) correspond to longer wavelengths of light. Human skin, regardless of pigmentation, also emits a long wavelength signal in the red-orange range.

When Riffell’s team repeated the chamber experiments with human skin-tone pigmentation cards, or a researcher’s bare hand, the mosquitoes flew back toward the visual stimulus only after CO2 was introduced into the chamber. When the researchers used filters to remove the long-wavelength signals, or the researcher wore a green glove, then the mosquitoes that had inhaled CO2 no longer flew toward the stimulus.

Genes determine the preference of these females for red-orange colors. Mosquitoes with a mutant copy of a gene needed to smell CO2 no longer showed a color preference in the test. Another strain of mutant mosquitoes, with a vision-related change that prevented them from “seeing” long wavelengths of light, were more colorblind in the presence of CO2.

“These experiments demonstrate the first steps mosquitoes take to find their hosts,” Riffell said.

The authors explained that further research is needed to determine how other visual and odor cues, such as skin secretions, help mosquitoes attack potential hosts at close range. Other species may also have different color preferences, depending on their preferred host species. But, in any case, these new findings provide new clues for mosquito control: color.

Reference study (in English): https://www.nature.com/articles/s41467-022-28195-x

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