For well over a half-century now, outdoorsmen and women have been slathering on DEET-based insect repellants to keep the skeeters at bay. We’ve (and scientists) always known that it works, but we’ve never really known why it works. But science never rests, and now researchers think they’ve discovered why mosquitoes dislike DEET so much: it makes us taste awful.

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_Fire up the citronella-scented tiki torches, and slather on the DEET: Everybody knows these simple precautions repel insects, notably mosquitoes, whose bites not only itch and irritate, but also transmit diseases such as West Nile virus, malaria and dengue. Now, Johns Hopkins scientists have discovered what it is in the bugs’ molecular makeup that enables citronellal (the aromatic liquid used in lotions, sprays and candles) and DEET, to deter insects from landing and feeding on you. A better understanding of these molecular-behavioral links already is aiding the team’s search for more effective repellents.

__In separate studies published on August 26, in Neuron and Current Biology, the Johns Hopkins researchers reveal how mosquitoes and other insects taste DEET — a man-made compound that’s been the most widely used insect repellent for more than 50 years — and smell citronellal, a commonly used botanical repellent. Scientists have long known that insects could smell DEET, Montell notes, but the new study showing taste molecules also are involved suggests that the repellent deters biting and feeding because it activates taste cells that are present on the insect’s tongue, legs and wing margins. “When a mosquito lands, it tastes your skin with its gustatory receptors, before it bites,” Montell explains. “We think that one of the reasons DEET is relatively effective is that it causes avoidance responses not only through the sense of smell but also through the sense of taste. That’s pretty important because even if a mosquito lands on you, there’s a chance it won’t bite.”
Two thoughts: One, anyone who’s ever accidentally given themselves a blast in the face with a can of OFF! could have told you the stuff tastes like radioactive waste. Second, I find it creepy that mosquitoes actually possess something called “gustatory receptors” that tell them what I taste like. Pass the bug spray…