It seems likely that gravid females respond to odour emanating from oviposition sites, since ovitrap charged with undiluted hay infusion collected significantly more eggs than those charged with tap water.
when ovitraps were exposed in mixed pairs, one charged with undiluted infusion and the other with tap water or 10% infusion, significantly more eggs were laid in the ovitrap containing tap water or 10% infusion than in their partners containing 100% infusion.
Possibly, odours from the undiluted infusion were an effective stimulant to which gravid females responded from a distance,