Effect of axenic larvae on the oviposition site selection by Aedes atropalpus.

Axenic rearing of Aedes atropalpus was performed from previously sterilized eggs to pupae in sterile 2500-ml culture flasks containing 500 ml of sterile culture medium. The larval density in the axenic rearing waters was approximately 500 larvae/liter. A series of experiments was conducted using respectively 6-, 9-, 12- and 19-day old axenic larval rearing water. All these tested waters were significantly preferred by the Ae. atropalpus females. Sterile, distilled water was also significantly attractive after only 48-hr immersion of axenic fourth-instar larvae. An axenic larval rearing water with higher larval density (900 larvae/liter) was however repulsive. The last experiment presents evidence for blocking of the attractant effect at high larval densities.