Gravid females of the mosquito Aedes aegypti avoid oviposition on m-cresol in the presence of the deterrent isomer p-cresol

Background: p-cresol (4-methylphenol) and its isomer m-cresol (3-methylphenol) have been shown to activate the same sensilla in aedes aegypti (linnaeus) mosquitoes. whereas p-cresol has been suggested to play a role in oviposition site choice,the behavioral significance of m-cresol is unknown. methods. here,we assayed the oviposition behavior of aedes aegypti towards p-cresol and m-cresol using cage assay. specifically we tested different concentrations of p-cresol (10-12-103 ppm) and m-cresol (10-1-103 ppm),the 1:1 mixture of the two compounds at 102 ppm,and the two individual compounds at 102 ppm together in the same cage. results: we show that (1) p-cresol is a stimulant at a low concentration and deterrent over a broad range of higher concentrations (10-8-103 ppm),while m-cresol was behaviorally ineffective,except for a deterrent effect at the highest concentration (10 3 ppm) (2) in concentration choice tests (different concentrations tested against each other),both compounds were deterrent only at the highest concentration (3) a 1:1 mixture of both compounds exhibited a deterrent effect on oviposition (4) when presented in separate cups but together in the same cage,p-cresol and m-cresol (102 ppm) both received significantly less eggs than water alone. conclusions: our results suggest that p-cresol is a strong oviposition deterrent with a stimulant effect at only a very low concentration,while m-cresol is not a deterrent per se. however,in the presence of p-cresol in the vicinity,m-cresol acts as a deterrent. this finding adds a new twist to the possible interactions of different odors in oviposition site choice: not only the source itself,but nearby odors also influence a mosquito's choice. © 2014 afify and galizia; licensee biomed central ltd.