DEET (N, N-diethyl-meta-toluamide) is the most effective and widely used insect repellent, but its mechanism of action is both complex and controversial . DEET acts on insect smell [2-6] and taste [7-11], and its olfactory mode of action requires the odorant co-receptor orco [2, 3, 6]. We previously observed that orco mutant female Aedes aegypti mosquitoes are strongly attracted to humans even in the presence of DEET, but they are rapidly repelled after contacting DEET-treated skin . DEET inhibits food ingestion by Drosophila melanogaster flies, and this repellency is mediated by bitter taste neurons in the proboscis . Similar neurons were identified in the mosquito proboscis, leading to the hypothesis that DEET repels on contact by activating an aversive bitter taste pathway . To understand the basis of DEET contact chemorepellency, we carried out behavioral experiments and discovered that DEET acts by three distinct mechanisms: smell, ingestion, and contact. Like bitter tastants, DEET is a feeding deterrent when ingested, but its bitterness per se does not fully explain DEET contact chemorepellency. Mosquitoes blood fed on human arms treated with high concentrations of bitters, but rapidly avoided DEET-treated skin and did not blood feed. Insects detect tastants both through their proboscis and legs. We show that DEET contact chemorepellency is mediated exclusively by the tarsal segments of the legs and not the proboscis. This work establishes mosquito legs as the behaviorally relevant contact sensors of DEET. These results will inform the search for molecular mechanisms mediating DEET contact chemorepellency and novel contact-based insect repellents.
Keywords: Aedes aegypti; DEET; bitter; contact chemorepellency; ingestion; insect repellent; mosquito; olfaction.
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Conflict of interest statement
Declaration of Interests
The authors declare no competing interests.
Orco Mutant Mosquitoes Lose Strong Preference for Humans and Are Not Repelled by Volatile DEETM DeGennaro et al. Nature 498 (7455), 487-91. PMID 23719379.Female mosquitoes of some species are generalists and will blood-feed on a variety of vertebrate hosts, whereas others display marked host preference. Anopheles gambiae a …
The Mysterious Multi-Modal Repellency of DEETM DeGennaro. Fly (Austin) 9 (1), 45-51. PMID 26252744. - ReviewDEET is the most effective insect repellent available and has been widely used for more than half a century. Here, I review what is known about the olfactory and contact …
Repellent and Deterrent Effects of SS220, Picaridin, and Deet Suppress Human Blood Feeding by Aedes Aegypti, Anopheles Stephensi, and Phlebotomus PapatasiJA Klun et al. J Med Entomol 43 (1), 34-9. PMID 16506445.A series of behavioral tests with Aedes aegypti (L.), Anopheles stephensi Liston, mosquitoes, and the sand fly Phlebotomus papatasi Scopoli in the presence of Deet, SS220 …
A Natural Polymorphism Alters Odour and DEET Sensitivity in an Insect Odorant ReceptorM Pellegrino et al. Nature 478 (7370), 511-4. PMID 21937991.Blood-feeding insects such as mosquitoes are efficient vectors of human infectious diseases because they are strongly attracted by body heat, carbon dioxide and odours pr …
EPA-Registered Repellents for Mosquitoes Transmitting Emerging Viral DiseaseRV Patel et al. Pharmacotherapy 36 (12), 1272-1280. PMID 27779781. - ReviewIn many parts of the United States, mosquitoes were previously nuisance pests. However, they now represent a potential threat in the spread of viral diseases. The Aedes a …
Cited by 3 PubMed Central articles
A Popular Indian Clove-Based Mosquito Repellent Is Less Effective Against Culex Quinquefasciatus and Aedes Aegypti Than DEETK Tan et al. PLoS One 14 (11), e0224810. PMID 31689339.Insect repellents are widely used as the first line of defense against mosquito bites and transmission of disease-causing agents. However, the cost of daily applications …
Commonly Used Insect Repellents Hide Human Odors From Anopheles MosquitoesA Afify et al. Curr Biol 29 (21), 3669-3680.e5. PMID 31630950.The mode of action for most mosquito repellents is unknown. This is primarily due to the difficulty in monitoring how the mosquito olfactory system responds to repellent …
DEET and Other Repellents Are Inhibitors of Mosquito Odorant Receptors for Oviposition AttractantsP Xu et al. Insect Biochem Mol Biol 113, 103224. PMID 31446031.In addition to its primary function as an insect repellent, DEET has many "off-label" properties, including a deterrent effect on the attraction of gravid female mosquito …