Researchers Clément Vinauger of Virginia Tech and Claudio Lazzari at the University of Tours report in the Journal of Experimental Biology that Aedes aegypti mosquitoes can learn to associate the smell of DEET with food and, in some cases, become attracted to it. In the main experiment the insects were restrained behind a fabric mesh while a bag of warm blood sat just out of reach. The scent of DEET was introduced as the mosquitoes began to feed. After four repetitions of this Pavlovian-style conditioning, more than 60% of the insects tried to feed when presented only with the smell of DEET.
In a follow-up test, mosquitoes chose between two human hands: one untreated and one coated with DEET at normal concentrations. Untrained mosquitoes avoided the treated hand, but trained mosquitoes were drawn to it. The same association formed when sugar was used instead of blood as the reward. Vinauger notes that the insect’s experience can change its response to chemicals and calls this a paradigm shift in how we think about repellents.
The authors do not recommend stopping DEET use. They say DEET remains one of the most effective repellents, especially where mosquito-borne diseases like dengue fever, Zika, yellow fever and chikungunya are common. They suggest that timing and concentration matter: reapplying regularly may keep protection continuous, and DEET on clothing may become less reliable as concentrations decline. The study builds on earlier lab work showing mosquitoes combine smell and vision, avoid people who swat at them, and respond to certain soap scents, and it underlines the growing importance of understanding mosquito behaviour as Aedes aegypti expands its range and insecticide resistance increases worldwide.
Difficult words
- associate — learn to link one thing with another
- conditioning — process of learning by repeated pairing
- paradigm shift — a major change in how people understand something
- repellent — a substance that keeps insects or animals awayrepellents
- concentration — amount of a substance in a mixtureconcentrations
- resistance — ability of organisms to survive control methods
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- How might learned attraction to DEET change the way people use repellents in places with mosquito-borne disease?
- What practical steps could reduce the risk if DEET on clothing becomes less reliable over time?
- How does the idea that mosquitoes combine smell and vision affect strategies for avoiding bites?
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