African Anopheles mosquitoes find us by our carbon dioxide–rich exhalation. But when they get close they turn away from our heads and dive for our feet—apparently their preferred snack spot.

Biologist Remco Suer believes he’s figured it the mosquito behavior, for his doctoral thesis at Wageningen University in the Netherlands. And the answer might help in the fight against malaria.

Previous research identified odors produced by 10 bacteria that live on human feet and that, in combination, are attractive to mosquitoes at close range. Suer's work shows that nine out of 10 of these odors are picked up by olfactory neurons under hairlike structures on the mosquitoes' mouthparts. Right nearby are some other key neurons—that recognize our CO2 from further away.

Suer discovered that five different bacteria scents, when isolated from the mix, actually block those CO2 neurons from doing their job. So if the bacterial odor molecule is present, the CO2 sniffers turn off, presumably to allow the mosquito to concentrate on the close-range foot target.

Suer imagines traps baited with these feet bacteria to attract mosquitoes and catch them before they can bite. It’s the next best thing to stepping on them.

—Cynthia Graber

[The above text is an exact transcript of this podcast.]