Think DEET keeps mosquitoes away? They may be learning to love it
Researchers found that yellow fever mosquitoes can learn to associate the smell of DEET with food — potentially weakening the world’s most widely used insect repellent
image:
Clément Vinauger, associate professor in the College of Agriculutre and Life Sciences at Virginia Tech.
view moreCredit: Virginia Tech
Every summer, millions of people spray themselves with DEET to keep mosquitoes away. But new research suggests mosquitoes may be able to learn to associate the repellent with food — and even become attracted to it.
The study, published in the Journal of Experimental Biology, was a collaboration between Clément Vinauger, associate professor at Virginia Tech, and Claudio Lazzari at the University of Tours in France.
"If someone applies DEET and the concentration fades over time, but a mosquito still manages to feed, the insect may begin associating that smell with a reward," said Vinauger, part of the Department of Biochemistry in the College of Agriculture and Life Sciences. "That's a possibility we should take seriously when we think about how repellents are used in the real world."
Yes, mosquitoes can learn
The study focused on the yellow fever mosquito, Aedes aegypti, a species that spreads dengue fever, Zika, yellow fever, and chikungunya, which infect tens of millions of people each year.
Researchers trained the mosquitoes using a form of Pavlovian conditioning — the same learning principle behind Ivan Pavlov’s famous experiments in which dogs learned to associate the sound of a bell with food.
Mosquitoes were restrained behind fabric mesh with a bag of warm blood positioned just out of reach. After the mosquitoes began to feed on the blood, researchers introduced the smell of DEET. After repeating the experiment four times, more than 60 percent of the insects tried to feed when presented with only the smell of DEET.
Next, mosquitoes were given a choice between two human hands — one untreated and one coated with DEET at normal concentrations. Untrained mosquitoes avoided the DEET-treated hand. Trained mosquitoes were drawn to it.
The researchers also found mosquitoes could form the same association when sugar, instead of blood, was used as the reward.
“The common assumption has always been that repellents work because of their chemistry — that DEET simply smells bad to mosquitoes and they flee or that its chemistry prevents mosquitoes from smelling us,” said Vinauger, who is also an affiliate of Fralin Life Sciences Institute's Center for Emerging, Zoonotic, and Arthropod-borne Pathogens. “But what we are showing is that the mosquito’s brain can rewrite that response based on experience. What the insect has learned matters just as much as what the chemical does. That, I think, is a paradigm shift.”
DEET is still the gold standard
The findings do not mean people should stop using DEET, Vinauger said. It’s still one of the most effective repellents available, particularly in regions where mosquito-borne disease is common.
"If you're in tropical regions where disease risk is real, you should use it," he said.
But the study suggests timing and concentration may matter more than previously understood.
"Instead of applying a lot at once, you may want to reapply regularly so it's always active and providing continuous protection," Vinauger said.
He added that treated clothing may also present challenges because DEET concentrations in fabric decline over time.
Better ways to outsmart mosquitoes
The study builds on years of mosquito learning and behavior research connected to Vinauger’s work. While pursuing his Ph.D. in Lazzari's lab in France, and later as a postdoctoral researcher at the University of Washington, Vinauger helped pioneer experiments showing mosquitoes can learn and remember odors associated with blood meals and defensive hosts.
At Virginia Tech, Vinauger’s lab studies how mosquitoes use sensory information to find hosts and adapt to changing environments. His team has shown that mosquitoes remember and avoid hosts who swat at them, combine smell and vision to track people with surprising precision, and gravitate toward and away from the smell of certain body soaps.
"Mosquitoes are remarkable at processing information about their environment," Vinauger said. "What we are trying to understand is not only how they detect us, but how their brains interpret those cues and turn them into behavior."
As Aedes aegypti expands into new regions and insecticide resistance grows worldwide, Vinauger said understanding mosquito behavior is becoming increasingly important for public health.
“We need to understand how mosquitoes keep outsmarting our control strategies,” Vinauger said. “And that takes understanding how they work — at the molecular level, the neural level, the behavioral level."
Original study: DOI 10.1242/jeb.251935
Journal
Journal of Experimental Biology
Article Title
Associative learning switches DEET valence from aversive to appetitive in Aedes aegypti
DEET insect repellent at risk: mosquitoes can learn it means dinner
Mosquitoes can learn that the scent of DEET means dinner, placing the quintessential repellent at risk
image:
A female yellow fever mosquito (Aedes aegypti), feeding on a bag of warm blood. Photo credit: Romina Barrozo
view moreCredit: Romina Barrozo
DEET is the gold standard for insect repellents, deterring ticks, flies and mosquitoes. Yet there may be a chink in the quintessential repellent’s armour. ‘If mosquitoes are repeatedly exposed to DEET, it becomes less effective as a repellent’, says Claudio Lazzari, from University of Tours, France, raising concerns that in certain situations the repellent may even begin to attract some biting insects. In research published in Journal of Experimental Biology, Lazzari, Clément Vinauger from Virginia Tech, USA, and colleagues have discovered that mosquitoes can learn to associate the smell of DEET with food, meaning that they could be more likely to bite people that smell of DEET, placing the indispensable repellent at risk.
Lazzari and colleagues made their discovery using a bizarre twist of Pavlov’s famous experiment, where dogs learned to associate the arrival of food with a ringing bell, but first the team had to find a way of confirming when the voracious insects were attracted to something tasty.
Knowing that yellow fever mosquitoes (Aedes aegypti) like nothing more than a meal of warm blood, David De Luca (University of Tours) restrained the insects behind a fabric mesh before offering them a bag of warm blood placed just out of reach, to see how enthusiastically the insects stabbed at it with their proboscises in the hope of grabbing a bite.
Sure enough, the insects were keen, especially when De Luca rewarded them by lowering the bag within reach, so they could feast. However, when the team offered the insects a blood meal when surrounded by the scent of DEET, the mosquitoes steered clear.
But could the insects learn to associate the scent of DEET with the offer of dinner? The team fed the insects with warm blood for 20 s, squirting the scent of DEET into the enclosure during the final 10 s of dining, repeating the procedure three more times before checking how the insect responded to the scent of DEET alone.
This time the mosquitoes went almost wild, with more than 60% trying to take a bite when they smelled a whiff of DEET.
And when the team offered the trained insects the choice between Ayelén Nally’s two hands (University of Buenos Aires, Argentina), one of which was bathed in DEET while the other was clean, the insects tried to bite Nally’s DEET-scented hand.
Finally, Charly Dufour (University of Tours) tried an alternative strategy, attempting to train the mosquitoes to associate a sugary treat with the scent of the repellent, and the mosquitoes got the idea, biting enthusiastically whenever they picked up the scent of DEET.
Mosquitoes can learn to associate the scent of DEET with the prospect of dinner, which could make people wearing DEET more attractive to biting insects under the right conditions.
‘If a mosquito bites someone who applied DEET to their skin several hours earlier and the concentration of the repellent is too low to repel the mosquito, but still strong enough for the insect to smell it, the mosquito may be more likely to bite people who smell of DEET’, says Lazzari.
The mosquitoes’ ability to learn to associate the repellent with food could also tell the researchers something about how the repellent works. ‘It is the information that DEET conveys to insects that may cause them to decide not to bite’, says Lazzari, explaining that DEET probably mimics some natural plant insect repellents, which keep insects at bay.
But, he adds that DEET is still the most effective insect repellent available, protecting people from mosquito-borne diseases. ‘It saves lives!’, he exclaims.
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REFERENCE: Lazzari, C. R., De Luca, D., Nally, A., Dufour, C. and Vinauger, C. (2026). Associative learning switches DEET valence from aversive to appetitive in Aedes aegypti. J. Exp. Biol. 229, jeb251935. doi:10.1242/jeb.251935
DOI: doi:10.1242/jeb.251935
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Journal
Journal of Experimental Biology
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Associative learning switches DEET valence from aversive to appetitive in Aedes aegypti.
Article Publication Date
28-May-2026
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