It’s the season when we find ourselves wondering (as we swat, smush, and shoo away mosquitoes despite four coats of bug spray) whether the suckers have learned to like their repellent. As it turns out…maybe.
New research has found that mosquitoes can learn to associate DEET, a chemical commonly used in bug repellents, with a potential meal.
“Earlier research has shown that mosquitoes can detect DEET, be repelled by its smell, and experience toxicity from it,” says Clément Vinauger, a researcher on the study and an associate professor at Virginia Polytechnic Institute and State University. “Our study shows that how mosquitoes interpret the molecule can also be modified by their prior experience with it, to the point of being attracted by it.”
The study used an adapted form of Pavlovian conditioning to observe if mosquitoes could be trained to anticipate a blood meal when encountering DEET. “Because DEET is such a strong repellent, we couldn’t present it to the mosquitoes and then offer them a blood meal as a reward,” says Vinauger. “Instead, we waited for them to be engaged in feeding before introducing the repellent.”
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The researchers observed that 60 per cent of the mosquitoes who fed while being exposed to DEET attempted to bite when presented with DEET on its own. When the same mosquitoes were allowed to choose between a hand treated with DEET and one without, the study again reported that 60 per cent gravitated toward the treated hand, while all untrained mosquitoes opted for the untreated hand.
This research may seem to suggest that DEET bug spray is useless, but Vinauger insists that it proves the opposite. “DEET is a highly effective repellent to naïve mosquitoes. The potential attraction was only observed in the specific laboratory scenario we designed,” he says. He adds that their research only reinforces the importance of following your repellent’s recommended dosage and application frequency so that mosquitoes don’t get the chance to associate the chemical with feeding.
“Mosquitoes are not human-hunting machines,” says Vinauger. “They continuously evaluate their environment and consider their past experiences to decide whether to bite someone.”
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