Study Finds Mosquitoes Can Learn to Associate DEET With Blood Meals

A study published in the Journal of Experimental Biology reports that mosquitoes can modify their response to DEET after prior exposure to the chemical during blood feeding. Researchers observed that 60 percent of mosquitoes that had fed on blood mixed with DEET later attempted to bite when presented with DEET alone.

In comparison, 17 percent of mosquitoes with no prior training showed the same behavior.

The experiments used a warm blood bag placed out of reach and a researcher's hand dipped in DEET. Nearly 60 percent of trained mosquitoes attempted to bite the treated hand, while untrained mosquitoes preferred the untreated hand. Professor Claudio Lazzari of the University of Tours stated that previous understanding held that repellents worked through toxicity, blocking host detection, or unpleasant odor.

The new data indicate that experience can alter this response.

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Nina Stanczyk of ETH Zürich University noted that mosquitoes have demonstrated learning abilities, but associating DEET with food is notable. Professor Francesca Romana Dani of the University of Florence said the duration of this learned association requires further study.

Lazzari clarified that the observed change occurred only under specific laboratory conditions and that DEET retains effectiveness in normal outdoor use.