“These mosquitoes really love me! Why aren't they biting you?" The reason why pests bother you, but not the person sitting next to you—or vice versa—probably comes down to a matter of scent.
Years ago, chemical ecologists at Rothamsted Research developed pyrethroid insecticides from a natural lead compound, pyrethrum, which is produced by chrysanthemum flowers. More recently, the company’s Chemical Ecology Group has been collecting the compounds which cause human body odor and determining which specific ones repel mosquitoes.
Scientists in the group use the foil “body bag” shown above to capture volunteers’ body odors, then study the make-up of the odors to determine which volatile chemicals the volunteers are emitting.
The group’s tests of the insect-repellant effects of several combinations of compounds that cause human body odor have shown promising results: The arm on the left below was treated with a mixture of chemicals emitted by people bugs tended to avoid before exposure to biting midges, while the one on the right was left untreated.
“The project reveals why some people are bitten more than others,” says Dr. James Logan, a Rothamsted researcher and lead author of these findings. “The results could be used to control mosquitoes that spread deadly diseases such as malaria. There is NO evidence,” he adds, “that food changes how attractive you are to mosquitoes.”
In a Wall Street Journal article on the research, Logan also notes that everyone emits chemicals that attract mosquitoes, but those who tend not to get bitten also emit chemicals that repel them.
Other research presented at the annual meeting of the International Society of Chemical Ecology focused on additional chemical compounds emitted by humans, cows, and wild dogs that attract and repel insect pests.
The Rothamsted research team isn’t sure when these products might become available to protect our arms from bugs that sting and bite, but human-B.O.-derived insect repellents could arrive at a store near you within the next few years.
In my next post I will take you back to Ranomafana National Park, Madagascar, to look at frogs, which are important (among other things) for insect control worldwide.
Photographs courtesy Rothamsted Research (top) and the University of Aberdeen (bottom)