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Water vapour is a pre-oviposition attractant for the malaria vector Anopheles gambaie sensu stricto

Okal, M.N.; Francis, B.; Herrera-Varela, M.; Fillinger, U.; Lindsay, S.W.

Water vapour is a pre-oviposition attractant for the malaria vector Anopheles gambaie sensu stricto Thumbnail


M.N. Okal

B. Francis

M. Herrera-Varela

U. Fillinger


Background: To date no semiochemicals affecting the pre-oviposition behaviour of the malaria vector Anopheles gambiae sensu lato have been described. Water vapour must be the major chemical signal emanating from a potential larval habitat, and although one might expect that gravid An. gambiae s.l. detect and respond to water vapour in their search for an aquatic habitat, this has never been experimentally confirmed for this species. This study aimed to investigate the role of relative humidity or water vapour as a general cue for inducing gravid An. gambiae sensu stricto to make orientated movements towards the source. Methods: Three experiments were carried out with insectary-reared An. gambiae s.s. One with unfed females and two with gravid females during their peak oviposition time in the early evening. First, unfed females and gravid females were tested separately in still air where a humidity difference was established between opposite ends of a WHO bioassay tube and mosquitoes released individually in the centre of the tube. Movement of mosquitoes to either low or high humidity was recorded. Additionally, gravid mosquitoes were released into a larger air-flow olfactometer and responses measured towards collection chambers that contained cups filled with water or empty cups. Results: Unfed females equally dispersed in the small bioassay tubes to areas of high and low humidity (mean 50% (95% confidence interval (CI) 38-62%). In contrast, gravid females were 2.4 times (95% CI 1.3-4.7) more likely to move towards high humidity than unfed females. The results were even more pronounced in the airflow olfactometer. Gravid females were 10.6 times (95% CI 5.4-20.8) more likely to enter the chamber with water than a dry chamber. Conclusions: Water vapour is a strong pre-oviposition attractant to gravid An. gambiae s.s. in still and moving air and is likely to be a general cue used by mosquitoes for locating aquatic habitats.


Okal, M., Francis, B., Herrera-Varela, M., Fillinger, U., & Lindsay, S. (2013). Water vapour is a pre-oviposition attractant for the malaria vector Anopheles gambaie sensu stricto. Malaria Journal, 12(10), Article 365.

Journal Article Type Article
Publication Date Oct 11, 2013
Deposit Date May 1, 2014
Publicly Available Date May 21, 2014
Journal Malaria Journal
Publisher BioMed Central
Peer Reviewed Peer Reviewed
Volume 12
Issue 10
Article Number 365
Keywords Anopheles gambiae, Oviposition, Water vapour, Gravid mosquitoes.


Published Journal Article (695 Kb)

Copyright Statement
© 2013 Okal et al.; licensee BioMed Central Ltd. <br /> This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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