For most people trying to avoid being eaten alive by mosquitoes, it is enough to know that DEET works. But for scientists and marketers hoping to invent or sell an even better bug repellent, the goal is to find out why DEET works.Now researchers at Rockefeller University in New York have solved a big part of that long-standing mystery, finding that DEET blocks a highly specific molecular pathway that tells a bug’s brain what it is smelling. In particular, it interferes with an insect’s ability to smell 1-octen-3-ol — a telltale ingredient of human breath — and the scent of lactic acid, an odoriferous hallmark of sweat. N, N-diethyl-meta-toluamide, or DEET, is the most widely used insect repellent in the world and was developed 60 years ago by the US Agriculture Department and the army. Among the many six-legged pests that find the stuff offensive are mosquitoes. Leslie Vosshall and colleagues measured the electrical pulses coming from nerves in the mosquito’s olfactory organ and found that DEET blocks a molecular smell receptor known as OR83b, which detects key components of human sweat and breath. Experiments in fruit flies confirmed the importance of that smell receptor. Details were published in the journal Science.
