A new study shows that a mosquito can sense carbon dioxide from 100 feet away and use it to find human skin tones.
The smell is telling them that something is out there, but their vision is telling them where it could be found, according to University of Washington neurobiologist Jeff Riffell. His team found that the insects are drawn to red and orange light and avoid greens and blues only if CO 2 is present.
The mosquitoes dart through the air in chaotic patterns. Researchers typically examine them in small boxes, but that doesn't recapitulate their natural behaviors. A seven-foot-long mosquito wind tunnel was built to mimic a more realistic environment. 16 cameras along the tunnel's edge captured live video that was stitched together to reveal each insect's flight path.
When Aedes aegypti mosquitoes were released into the tunnel, they didn't look at objects colored to match human skin until carbon dioxide was added. The mosquitoes were attracted to the objects. The attraction was stopped by the orange and red light. In another experiment, the researchers introduced a new type of mosquito that had no vision at all. They stopped swarming toward human skin tones, as well as mutating a CO 2 -sensingreceptor.
It seems likely, given that mosquitoes do not have a red-sensitive receptor, according to Almut Kelber, a sensory biologist at Sweden's Lund University.
Other insects use smell to make decisions. Kelber says that female Asian swallowtail butterflies make color choices based on the smell. They preferentially land on blue objects in a laboratory setting. She says that swallowtails move toward green when they smell a host plant. They prefer red when they smell oranges or lilies.
He wants to develop better mosquito traps. He says that many traps have white components.
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