PARIS, France (AFP) — Mosquitoes can learn to associate the smell of the world’s most common insect repellent with a tasty meal — and after training can even prefer to bite people who have been sprayed with it, an experimental study said Thursday.
The surprising results, which were conducted “under very specific conditions” in the lab, do not “call into question the effectiveness” of the repellent DEET, lead study author Claudio Lazzari told Agence France-Presse.
For the experiment, the mosquitoes were put in a fabric mesh enclosure, then presented with a bag of warm sheep’s blood to observe how eagerly they fed on it.
Unsurprisingly, the Aedes aegypti mosquitoes — which spread deadly diseases such as dengue fever, Zika, yellow fever and chikungunya — leapt at the chance.
When the smell of DEET was introduced, the mosquitoes moved away, which was also expected.
Next, the scientists fed the insects warm blood for 20 seconds, releasing DEET during the last 10 seconds.
That part was repeated three times before the mosquitoes were exposed to solely the scent of the repellent.
This time, more than 60 percent of the insects tried to bite the fabric — even though there was no blood.
Then, one of the scientists offered up their hands — one clean, the other coated with DEET — to the trained mosquitoes to see which one they would bite.
The result was beyond doubt: the insects preferred the hand covered in repellent.
The scientists had similar results when they repeated the experiment using sugar instead of blood, because mosquitoes mostly feed on plant nectar in the wild.
While the mosquitoes were trained relatively quickly during the experiment, in nature “very specific conditions would be needed for things to happen the same way,” Lazzari emphasized.