Insects reversed: Have mosquitoes learnt to love insect sprays?
5/6/2026
Translation: machine translated
Researchers have taught mosquitoes to associate the odour of mosquito spray with food. Are repellents now ineffective? What's really behind the study.
You've hidden behind a mist of mosquito spray, waited a moment - and then a mosquito bites again. Annoying, but not uncommon. Now a new study in the Journal of Experimental Biology supposedly provides an explanation for this and is causing a stir: Researchers from the University of Tours in France have trained mosquitoes in the laboratory so that they no longer avoid the common repellent DEET, but instead fly specifically at it. They have effectively reversed the insects' behaviour.
At first glance, this sounds like a problem for anyone who relies on insect repellents. However, a closer look at the study shows that there is no need to panic: mosquito sprays remain as effective as ever.
Mosquito training according to the Pavlov principle
The researchers from France used a principle from behavioural research to investigate the learning ability of the yellow fever mosquito (Aedes aegypti) - a species that transmits the dengue virus, among other things, but is not native to this country. To do this, they repeatedly coupled a stimulus with a reward in order to condition the animals. This type of experiment is known from Ivan Pavlov, who taught dogs to salivate in response to the sound of a bell «» by repeatedly making this sound when he fed them.
The yellow fever mosquitoes in the current study were fed blood meals in the laboratory while DEET was in the air. This scenario was repeated over a longer period of time. After some time, the behaviour of some of the mosquitoes changed. Instead of avoiding the DEET odour, they flew towards it. For these animals, the substance was no longer a warning signal, but an indication of food. The effect was practically reversed through targeted conditioning.
Smart insects: Learning ability in mosquitoes is not new
This finding did not come out of the blue. Previous studies have already shown that mosquitoes can associate odours with negative or positive experiences - for example with defence movements or successful bloodsucking. The new study is in line with this research, but goes one step further because it focuses on a classic repellent agent.
The researchers were able to show that even a substance that normally repels mosquitoes can be positively linked under certain conditions.
Why this does not mean that insect repellent is ineffective
The mental leap is therefore obvious: If mosquitoes can learn to perceive DEET positively, this explains why they bite despite the spray. But that is too short-sighted.
The experiments took place under highly simplified laboratory conditions. No human skin, no sweat, no breathing air, no movement. In reality, however, DEET is just one signal among many - and competes with body odours, carbon dioxide and heat. It is only in this interaction that its protective effect unfolds. In addition, not all mosquitoes in the experiment learnt the new classification. It remains to be seen whether the effect is stable or even noticeable outside the laboratory.
DEET also does not work like a single switch that you flip, but has different mechanisms of action. It directly influences certain insect odour receptors. As a result, human odours are masked and the mosquito's orientation is disrupted. These effects persist even if individual animals have learnt to classify the substance differently.
Why do we get bitten despite using mosquito repellent?
There are usually unspectacular reasons why the occasional mosquito gets through despite the spray: The repellent is unevenly distributed, is washed off by sweat, the volatile active ingredient evaporates, or there are simply an extremely large number of mosquitoes out and about. No repellent offers 100 per cent protection - this was already the case before this study.
Important findings for the future of infection research
The work will be particularly exciting when looking ahead. When it becomes clearer how flexibly mosquitoes react to odours and what they can learn, it will be possible to work more specifically on new protective substances, attractants or traps. This is essential basic research, especially for regions where mosquitoes transmit dangerous diseases.
However, the all-clear has been given for us: Anti-Brumm and co. remain effective and a bite despite a spray has more mundane reasons than newly conditioned insect brains.
Header image: Jaromir Chalabala/Shutterstock
Anna Sandner
Senior Editor
Anna.Sandner@galaxus.deScience editor and biologist. I love animals and am fascinated by plants, their abilities and everything you can do with them. That's why my favourite place is always the outdoors - somewhere in nature, preferably in my wild garden.
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