title: Gravid females of the mosquito Aedes aegypti avoid oviposition on m-cresol in the presence of the deterrent isomer p-cresol.
abstract: 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 (103 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.
authors.affiliation: Neurobiology, University of Konstanz, 78457 Konstanz, Germany. ali.aliafify@fulbrightmail.org.
authors.forename: Ali
authors.initials: A
authors.lastname: Afify
authors.forename: C Giovanni
authors.initials: CG
authors.lastname: Galizia
mesh_terms: D000330:Aedes / Q000502:physiology*; D000818:Animals; D001681:Biological Assay; D003408:Cresols / Q000737:chemistry* / Q000494:pharmacology*; D005260:Female; D010058:Oviposition / Q000187:drug effects*
chemical_list: D003408:Cresols; C032538:4-cresol