Three scientists from Sweden and the UK have shown that yellow fever mosquitoes have developed a resistance to DEET, a common insect repellent. Through laboratory tests, they found that the mosquitoes can no longer detect the smell of DEET due to a sensory cell on their antenna becoming inactive. This is the first evidence that mosquitoes can become resistant to repellents through hereditary mutations. The researchers warn that widespread use of DEET in a limited area could lead to other mosquito species developing a resistance as well. More study is needed to understand the exact mechanism behind the mosquitoes' new resistance.