Why do mosquitoes appear to bite some individuals more than others? That’s a question that Vanderbilt biologist Jason Pitts almost always gets asked when people find out he studies mosquitos for a living.
Pitts is part of a research team that’s developing new attractants and repellants to combat malaria and other mosquito-borne illnesses. He said:
We have a general answer to that question: It has to do with individual variations in body odor, but right now we don’t understand the specific combination of odorants that mosquitoes find most attractive.
The source of the aromatic compounds that produce body odor are bacterial colonies that exist on human skin, particularly in dark, moist areas such as the arm pits and between the toes.
Pitts and his colleagues have discovered that mosquito antennae are filled with hundreds of tiny odor receptors, which are individually tuned to detect specific odors. While they have identified dozens of aromatic compounds that trigger the mosquito’s antennae, the researchers haven’t discovered one that acts as a super-attractant. Pitts said:
The experimental evidence strongly supports the conclusion that mosquitoes are attracted by blends of odors, rather than a single odorant. Individual compounds, on the other hand, can act as powerful repellants.
So what are these compounds that repel mosquitos?
Natural repellants such as clove oil, citronella, lemon grass, eucalyptus, castor oil, peppermint, lavender and cedar oil all work to a limited extent, Pitts said. He added that almost all of them are less effective than the synthetic repellant DEET.
Actually, odors combined with heat are the basis of the mosquitoes’ short-range detection system, Pitts said. The pesky insects also have a long-range system that allows them to track down potential prey from more than 100 yards away. The mosquitoes do so, in part, by sensing the carbon dioxide in human breath. When we exhale, our breath contains four to five percent more carbon dioxide than the surrounding air and mosquitos can detect this difference. Pitts said:
As you exhale, your breath is carried by air currents as a series of bubbles enriched in CO2 that can persist for some time,” Pitts said. “Female mosquito flight is activated by CO2 and she can dart upwind from bubble to bubble in pursuit of her target.
According to some studies, mosquitoes are attracted more strongly to human breath after a person has downed a beer or another alcoholic drink, he added.
Eleanor Imster has helped write and edit EarthSky since 1995. She was an integral part of the award-winning EarthSky radio series almost since it began until it ended in 2013. Today, as Lead Editor at EarthSky.org, she helps present the science and nature stories and photos you enjoy. She also serves as one of the voices of EarthSky on social media platforms including Facebook, Twitter and G+. She and her husband live in Tennessee and have two grown sons.