Electrophysiological investigation of larval water and potential oviposition chemo-attractants for Anopheles gambiae s.s.

Potential Anopheles gambiae s.s. breeding sites were sampled in rural sites in the Tanga region of Tanzania. Sites containing the largest numbers of A n. gambiae larvae were small, shaded pools and rice fields. Water samples w ere collected from the larval sites and these, together with ether extracts of the water samples, were active in electro-antennogram (EAG) studies wit h female mosquitoes from a laboratory colony of Anopheles (Cellia) gambiae KWA. EAG response thresholds varied for 10 randomly selected water samples, from 0.01%-100% dilution for the whole water samples and from 0.001%-1.0% dilution for the ether extracts. Potential chemical components of the water samples were also electrophysiologically active with female An. gambiae an tennae; thresholds varied from 1 ng (3-methylindole and indole) to 10 mu g (m-cresol and 4-methylcyclohexanol).