There are good evolutionary reasons that some species of mosquito developed a taste for humans: We tend to live in groups and are never far from water, which mosquitoes need to breed.

But by mutating a gene responsible for smell, researchers at Rockefeller University report in a new study that they produced a generation of mosquitoes incapable of sniffing out human targets.

“The job of Aedes aegypti is to hunt down humans and ignore all other animals,” said an author of the study, Leslie B. Vosshall, a professor of neurogenetics at Rockefeller, referring to the species of mosquito in the experiment. “So we made these mutants that really have a hard time telling humans from nonhumans.”

To create the mutant mosquitoes, Dr. Vosshall and her colleagues altered an odor receptor, orco. Not only did the resulting mosquitoes struggle to tell the difference between humans and other animals, but they were unable to detect the presence of DEET, the insect repellent, before it was too late. “They happily fly toward a human arm slathered in DEET,” Dr. Vosshall said. “It’s only once they land that they realize there’s something really horrible on the person.”