Scientists have found that mosquitoes can be trained to connect the smell of a widely used repellent (diethyltoluamide, or DEET) with food.<\/p>\n
Their discovery could have broader implications for ongoing mosquito control.<\/p>\n
Claudio Lazzari, lead author on the paper and a researcher at the University of Tours in France, said this was the first time anyone had reported mosquitoes being attracted to DEET.<\/p>\n
Professor Lazzari said the findings suggested low concentrations from hours-old repellent could be too weak to repel mosquitoes, but strong enough to signal food.<\/p>\n
But he emphasised the findings were only short-term, and people should keep using repellents according to the instructions on the product.\u00a0<\/p>\n
“DEET remains the gold standard for repellents,” Professor Lazzari said.<\/p>\n
“It is an effective means of protecting yourself against mosquito bites and can save lives in areas where mosquito-borne diseases are prevalent.”<\/p>\n
Teaching mosquitoes to find repellent delicious<\/p>\n
The researchers ran a series of experiments with a species of mosquito (Aedes aegypti) that can spread dengue fever, yellow fever, Zika virus and chikungunya.<\/p>\n
These diseases kill tens of thousands of people<\/a> worldwide each year (although Aedes mosquitoes don’t carry malaria, which is the largest mosquito-related killer).<\/p>\n The researchers put mosquitoes one-by-one into a small tube covered with mesh, set up with a mechanism for pumping the smell of DEET through, and warm bags of sheep’s blood to feed from.<\/p>\n All mosquitoes in the experiment were female, since only female mosquitoes feed on blood. (Supplied: Romina Barrozo)<\/p>\n The researchers then submitted some of their mosquitoes to “Pavlovian” conditioning, named after 19th century Russian physiologist Ivan Pavlov, who taught dogs to link the sound of a bell with dinner.<\/p>\n After letting the mosquitoes feast on blood for 20 seconds, the researchers wafted DEET into their tubes for 10 seconds.<\/p>\n They ran this training regimen three times, then tested the mosquitoes’ DEET response by spraying the smell into the enclosure without adding food.<\/p>\n Sixty per cent of the trained mosquitoes tried to bite at non-existent blood bags, suggesting they’d learned the smell of DEET signalled dinner.<\/p>\n Each mosquito was discarded after testing. (Supplied: Romina Barrozo)<\/p>\n To see how they’d respond to human prey, one of the researchers dipped one of her hands in DEET.<\/p>\n A few minutes later, she offered her DEET-covered hand and her untreated hand to mosquitoes at either end of a mesh-covered tube.<\/p>\n More than half the DEET-trained mosquitoes tried to bite the DEET-covered hand, while untrained mosquitoes all opted for the untreated hand.<\/p>\n “The experiment was conducted in such a way that the mosquitoes could never reach the experimenter,” Professor Lazzari said, adding that the mosquitoes were a lab-bred variety that carried no diseases.<\/p>\n The researchers also repeated the test with sugar instead of blood, finding that a different reward was still equally enticing to the mosquitoes.<\/p>\n Mosquito preferences can be changed<\/p>\n While DEET has been widely used since the 1950s, scientists still aren’t sure exactly why it repels insects.<\/p>\n “The general consensus was that repellents worked solely because of their chemical properties: either they were toxic or unpleasant to mosquitoes, driving them away; or they blocked their ability to detect humans,” Professor Lazzari said.<\/p>\n But he said their findings, along with other more recent research, suggested that mosquitoes’ response to repellent was more plastic.<\/p>\n “Mosquitoes are not programmed robots, but cognitive creatures.”<\/p>\n Professor Lazzari said other species of mosquito could probably be trained in a similar way, but this would need to be tested.<\/p>\n Mozzie bite myths busted<\/a><\/p>\n How much do you actually know about avoiding itchy bites \u2014\u00a0and which “cures” are just old wives’ tales?<\/p>\n Thomas Schmidt, an insect researcher at the University of Sydney who wasn’t involved in the study, said that it was a very interesting result.<\/p>\n “A mosquito is incredible \u2014 it’s like a whole advanced set of nervous sensory systems with wings,” Dr Schimdt said.<\/p>\n “There’s bound to be so much complexity within the mosquito nervous system that we don’t know about yet, and we’re really just uncovering that at the moment.”<\/p>\n Wild mosquitoes may be different<\/p>\n Dr Schmidt said that mosquitoes can have very complex behavioural responses to the world around them.<\/p>\n But, he said, the highly synthetic environment the mosquitoes were tested in made it hard to draw conclusions about how they’d act in the wild.<\/p>\n For a start, the mosquitoes were trained with sheep’s blood, when Aedes aegypti feed almost exclusively on humans.<\/p>\n The mosquito strain the researchers used had also been bred in labs since the 1960s, meaning they may have diverged from their modern wild cousins.<\/p>\n “These mosquitoes are a bit different in how they might behave compared to mosquitoes that have never been kept in the lab,” Dr Schimdt said.<\/p>\n The Aedes aegypti mosquito is not native to Australia, but is found in Queensland. (iNaturalist: Jorge J. Rodr\u00edguez Rojas, CC BY-NC 4.0<\/a>)<\/p>\n While there’s no evidence of mosquitoes becoming attracted to DEET in the wild, Dr Schmidt said there had been reports of mosquitoes showing complex behaviour in response to the world around them.<\/p>\n “For instance, there are reports of mosquitoes that are able to evade insecticides by flying up in the air while the insecticides are being used at street level, and then coming back down to the ground hours later after the insecticides have dispersed,” he said.<\/p>\n![\"Mosquito](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/05\/15a0a2702835e8f86157a75aa0b76d90.jpeg\")
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