Study summary
Associative learning switches DEET valence from aversive to appetitive in Aedes aegypti
Lazzari CR, De Luca D, Nally A, Dufour C, Vinauger C
- Study type
- Lab
- Year
- 2026
- Published in
- Journal of Experimental Biology 229(10):jeb251935
- Evidence strength
- Limited evidence
Summary
Laboratory neuroethology study testing whether Aedes aegypti mosquitoes can learn to associate DEET odor with a reward. Individual mosquitoes underwent Pavlovian conditioning that paired brief DEET exposure with an appetitive context (a warm blood source held just out of reach, or a sugar reward), and their response was scored using a validated biting attempt response. Note: this measures learned odor preference, not skin bite-protection, so it does not slot into complete-protection-time evidence and carries no measured protection arms.
Key findings
After conditioning, trained mosquitoes reversed the innate meaning of DEET, shifting from avoiding the odor to being attracted to it. The valence flip held for associations with both blood feeding and plant sugar feeding. Critically, this conditioning acts only on DEET's olfactory channel. DEET also repels through a separate contact mechanism: Aedes aegypti detect it through chemoreceptors on their legs (tarsi) and pull back from treated skin even when smell is absent. Prior work shows olfactory-deprived Aedes aegypti will land on DEET-treated skin but still refuse to blood-feed after contact (DeGennaro et al. 2013; Dennis, Goldman and Vosshall 2019). So a learned attraction to DEET odor does not defeat the on-skin contact deterrent, and public-health guidance continues to rate DEET as a first-line, highly effective topical repellent.
Limitations
Single species (Aedes aegypti) under controlled laboratory conditioning of individual mosquitoes. The Pavlovian pairing (seconds of DEET odor next to an unreachable reward) is highly artificial, and there is no evidence that wild populations acquire this association in the field. The endpoint is odor valence measured by a biting attempt response, not a complete-protection-time trial on treated skin. Because the study conditions only the olfactory channel and leaves DEET's tarsal contact deterrent untouched, its practical relevance to real-world personal protection is unestablished. Findings should be read as a mechanistic curiosity about mosquito learning, not as evidence that DEET is losing effectiveness.