Scientists find mosquitoes are attracted to certain body odour Mosquitoes find victims by detecting carbon dioxide and skin odour They do this using olfactory neurons situated around the insects" mouths Researchers tested these receptors using odour taken from human feet It found certain chemicals can mask this smell of human odours Chemicals that smell like green fruit, for example, shut the sensors down for around five minutes These results will be used to design more effective mosquito repellent Why do mosquitoes bite some of us and not others? New research has discovered how the insects detect even the faintest of human body odours when searching for potential victims. It's been known for some time that female mosquitoes use specific sensors around their mouths to detect carbon dioxide being exhaled from humans and animals. And now researchers from the University of California Riverside have discovered the blood-sucking insects also use these same sensors to detect body odours - especially the smell of feet. Researchers from the University of California Riverside discovered female mosquitoes use sensors around their mouths to detect human odours, as well as carbon dioxide, and certain chemicals including compounds that smell like green fruit can temporarily mask these smells Deet, the widely used insect repellent, is becoming less effective at repelling mosquitoes, according to research from the London School of Hygiene and Tropical Medicine. A landmark study found that while mosquitoes are initially repelled by the substance, they ignore it if they are later exposed to it again. The study tested the response to Deet on Aedes aegypti mosquitoes, which are notorious for biting during the day and are capable of transmitting dengue fever and yellow fever viruses. Olfactory neurons found in what's called the mosquito's maxillary palp - sensors found around the insects" mouths - are used to detect carbon dioxide. These sensors can be inhibited using a chemical called butyryl chloride and this compound temporarily stops the insects from being able to sense carbon dioxide. Scientists knew mosquitoes were additionally attracted to body odour, but weren't sure which sensors they used. The California researchers took samples of human odours by getting participants to rub their feet on glass beads. They then put these beads in the same room as the Aedes aegypti and Anopheles gambiae species of mosquitoes to find the insects were able to almost immediately identify the smelly beads. To see if the same carbon dioxide sensors were responsible for identifying human odours, the scientists gave each insect a dose of butyryl chloride before putting them in the room with the beads again. This time, only a fifth of the insects were able to locate the beads with the foot odour on. The researchers asked participants to rub their feet on glass beads. They put these beads in the same room as the Anopheles gambiae, pictured. The insects were able to almost immediately identify the beads using olfactory neurons on sensors around their mouths. These results were then used to test a variety of repellents These results were then used to test a variety of repellents, as well as see which chemicals and smells attracted the mosquitoes most effectively. Minty smells attracted the insects the most, while green fruit hid the smell of human odour for around five minutes. Each of the chemicals used had been tested and approved for use by humans. Scientists can now use these findings to create a range of repellents, and mosquito traps, to help curb the spread of malaria, for example. "Female mosquitoes that transmit deadly diseases locate human hosts by detecting exhaled CO2 and skin odour," the researchers said. Analysis of the CO2 receptor ligand space provides a foundation for understanding mosquito host-seeking behavior and identifies odors that are potentially safe, pleasant, and affordable for use in a new generation of mosquito control strategies worldwide.