Mosquitoes prefer the color red

You walk down a street and the delicious aroma of freshly baked flour reaches you. That’s the sign for a nearby bakery. He begins to track her with his nose. She finds. He comes in. On the counter spreads a panoply of warm pasta of different colors. Freshly made bream are the most appetizing. They all appeal to him, but he chooses one because of the color. He is acting exactly like a mosquito: he smells, tracks scent, notices heat, and chooses by color.

Spring is approaching and mosquito larvae begin to transform into adult insects. There are more than 3,000 species of mosquitoes and they are no joke. These tiny insects, whose maximum weight is just over two milligrams, contribute to more than 725,000 human deaths a year.

There are no other creatures as deadly as mosquitoes.

Avoiding being bitten by mosquitoes, especially when around you are some dangerous exotic visitors carrying viral diseases, may depend among other things on the clothes you wear.

Research led by scientists at the University of Washington (USA) indicates that the hematophagous female of a species of mosquito, Aedes aegyptiit flies towards specific colors, including red, orange, black, and cyan, while ignoring other colors, such as green, purple, blue, and white.

In addition to being one of the most fearsome mosquitoes specialized in humans, to which they transmit Zika, yellow fever and dengue, Aedes aegypti they thrive in tropical urban habitats in the Americas and Asia, where they have specialized in biting people to the point that 95% of the females’ food comes from human blood.

For biting insects such as mosquitoes, tsetse flies, and kissing bugs, vision plays an essential role in several behaviors, including flight control, locating egg-laying sites, and fleeing from impending danger.

Once in flight, there are three signals that attract blood-sucking mosquitoes:

Mosquitoes also respond to color

Color point experiments used in the research by scientists at the University of Washington conclude that, in addition to these three stimuli, female mosquitoes respond to visual cues and prefer certain wavelengths of the light spectrum.

Humans with normal vision detect different wavelengths of light as different colors: 650 nanometers (nm) appear red, while 450 nanometers appear blue.

The scientists tested the behavior of the mosquitoes in miniature test chambers in which specific odors were sprayed, different visual patterns were placed in the form of circles of different colors and a hand was introduced, a highly appetizing piece for any hungry blood eater.

When no CO₂ was introduced, and therefore no olfactory stimulus was present, the mosquitoes ignored any colored dots in the chamber regardless of what color they used. After introducing a puff of CO₂ into the chamber, the mosquitoes continued to ignore the dot if it was green, blue, or purple.

But whether the dot was red, orange, black, or cyan, they inevitably flew toward it.

When experiments were repeated with cards colored in human skin tones or when a bare hand was inserted into the chamber, the mosquitoes flew towards the visual stimulus only after CO₂ was introduced.

That done, if the researchers used filters to remove the long-wavelength signals, or if the hand was covered with a green glove, the CO₂-alerted mosquitoes disdained the stimulus.

Numerous cosmetic industry research papers have shown that human skin, regardless of tone or pigmentation, has its lowest peak at the green wavelength (530 nanometers) and highest reflectance at long wavelengths (600 nanometers). ).

daytime mosquitoes as Aedes aegypti they are most active in the mornings and late afternoons, the periods when longer wavelengths dominate. For its part, the twilight as Anopheles stephensi and Culex quinquefasciatus they are especially active during moonlit nights, when long wavelengths also dominate.

A pioneering work from 1938 demonstrated the preferences of Aedes aegypti by certain colors of clothing. Females showed the greatest preference for surfaces with a low reflection factor, especially black. Red was more attractive than various colors with a lower reflection factor. Yellow and khaki turned out to be the most repellent colors. The experiments on which that work was based concluded that, although the mosquitoes did not stop perching on a repellent color, the number of those that did so decreased with a statistically significant frequency.

mosquitoes like red

Researchers have certified the attraction of mosquitoes to red cloth. To our misfortune, long-wave radiation typical of red is also emitted from human skin. The tone of your skin does not matter: in the eyes of the mosquitoes, all of us who do not have black skin (the most attractive for them) emit a powerful red imprint.

Filtering those attractive colors into our skin, or wearing clothes that avoid those colors could be one way to prevent mosquito bites.

Knowing what colors do or do not attract hungry mosquitoes can help design better repellants, traps and other methods to keep them at bay, but what is more interesting for future research is that preferences for smells and colors are genetically determined.

question of genes

Mosquitoes with a mutant copy of a gene needed to smell CO₂ showed no color preference in the test chamber. Genes also determine the preference of females for red-orange colors. Organic photosensitive compounds contain proteins called opsins.

The opsin-2 gene, which is tuned to the green to orange band of the visual spectrum, is highly expressed in the mosquito retina. The results of this and other studies suggest that opsin-1 and opsin-2 play an important role in determining preference for visual attraction to human skin.

More research is needed to identify the opsins involved and the neural circuits that help mosquitoes attack potential hosts.

CRISPR gene editing to modify a gene that determines sexual development in mosquitoes, a method that is showing good results in the extinction of the mosquitoes responsible for malaria, paves the way for plans to use genetically modified mosquitoes to eradicate wild populations of insects that transmit diseases such as malaria, dengue, yellow fever or Zika.