I HAVE OFTEN wondered how mosquitoes are so good at finding us. A bite from the mosquito that carries dengue can be more than annoying. Now a study has just identified one way they zero in on people. It is because mosquitoes just like the look of our skin.
Researchers discovered something that could help ward off disease-carrying mosquitoes. Mosquitoes are attracted to a select few colors, and especially ones with long wavelengths of light. These hues are red — the same wavelengths given off by human skin. That info could lead to the design of better traps to lure mosquitoes away from people.
Testing a mosquito’s color preference is not simple since the apparent color of an object doesn’t just depend on the wavelengths of light it gives off. It also can be affected by the brightness of that light and its contrast against surrounding colors.
To do that, a software engineer designed a test chamber that was 450 mosquito-body-lengths long. Lined with cameras, it recorded the insects’ flight patterns. Two small colored disks laid on the floor of the chamber.
Since the researchers wanted to know if mosquitoes were attracted to certain colors, the disks couldn’t be the darkest or brightest objects in the chamber. Otherwise, it would be unclear if the mosquitoes were attracted to the disks’ color, contrast or brightness. So, the researchers projected a checkerboard pattern onto the floor of the chamber and gray along the walls. That way, if the mosquitoes went to the colored disks, it could only be due to the disks’ color.
The researchers released about 50 starved Aedes aegypti mosquitoes into the CO2-sprayed chamber at a time. Cameras recorded where the mosquitoes flew and how they interacted with the colored disks. Whichever disk the mosquitoes hovered around longer would be the color the insects preferred.
About 1.3 million mosquito flights later, the team had its results. Before CO2 was sprayed in the chamber, the mosquitoes ignored all the colored disks. With CO2, mosquitoes ignored any disk that was green, blue or purple. But the insects did fly toward disks that were red, orange or cyan (light blue). These colors, apparently, were very enticing. The mosquitoes seemed to especially like red.
To further investigate if vision plays an important role to find humans, the team placed disks with different skin tones inside their test chamber. But the bloodsuckers didn’t seem to prefer any particular skin colors. All were equally attractive.
The team tested three other mosquito species that feed on people. Red hues attracted each of them, too. But these mosquitoes differed in what other colors they seemed to prefer. There still is much to learn about how mosquitoes see and navigate their world. It seems obvious that mosquitoes might be attracted to reds since that is the color human skin appears to them. Still unsure is why are they also attracted to a light blue. And, importantly, how might these new data on color preferences be used to design better mosquito traps or repellents. By Manny Palomar, PhD (EV Mail August 15-21, 2022 issue)
