Research now shows that mosquitoes may bite the hand that feeds them Deet — at least in time.
The commonly used chemical — which is the gold standard ingredient approved by the Environmental Protection Agency (EPA) to act as a mosquito repellent — has recently been shown to potentially attract the pesky insects, as they’ve come to associate the chemical with a fleshy meal.
Professor Claudio Lazzari of the University of Tours in France told The Guardian that scientists previously believed that repellants worked solely due to their chemical makeup — whether through their toxicity, blocking the pests’ ability to find humans, or simply through their unpleasant-smelling nature.
Previous research suggested mosquitos weren’t as bothered by Deet (which has the chemical name N,N, -diethyl-meta-toluamide) after first exposure, but the team conducting the new study said the reason behind this was unclear.
However, the new research — detailed in the Journal of Experimental Biology — suggests that mosquito’s reaction to Deet can be “modified by experience.”
“We believe this represents a significant change in our understanding of repellants,” Lazzari told The Guardian.
Initially, the researchers observed that the trapped mosquitos in their study tried to bite a warm bag of blood that was just out of reach. Subsequently, they found that 60 percent of the pesks that fed when presented with this — mixed with Deet — showed biting attempts when exposed to just Deet in future feedings.
This was put up against 17 percent of mosquitos with no prior training; 13 percent of the insects who were presented with just Deet; 17 percent that had fed on warm blood without Deet exposure; and 23 percent that had fed on warm blood before and had Deet exposure, but not at the same time.
Another test revealed that nearly 60 percent of mosquitos that had fed on blood while exposed to the chemical attempted to bite a researcher’s Deet-dipped hand afterwards. On the other hand, the untrained pests all attempted to nibble on the researcher’s other untreated hand.
Dr. Nina Stanczyk at ETH Zürich University explained to The Guardian that while mosquitoes have been long observed to have “impressive learning abilities,” that they are able to “associate such a strong repellent smell with their food and are then attracted to it afterwards is remarkable.”
“(It’s) important for us to be aware of for the future,” Stanczyk told the outlet.
Don’t ditch the Deet just yet, though. Lazzari clarified that the chemical does not lose its effective nature through use in normal, outside-world conditions.
“(It’s) only under specific laboratory conditions designed to reveal how it works on mosquitos,” she explained.
“Although a single mosquito can take multiple blood meals, they do so every few days, so it’s important to evaluate how long the memory of a blood meal taken in the presence of Deet will last,” Professor Francesca Romana Dani, an entomologist at the University of Florence, added.
