Abstract
The first step in studying the foraging strategy of female adults of the solitary parasitoid, D. rufiventris, of the leaf mining fly, P. ranunculi, was to determine whether they can effectively discriminate already searched from unsearched leaflets and also whether they use a marking pheromone for this purpose. 1) The female parasitoid did not search for hosts as long on already searched leaflets as on unsearched ones. 2) Leaflet discrimination of this sort would be neither ascribed to her memory of the already searched leaflets nor to encounters with parasitized hosts present in those leaflets. 3) This discrimination disappeared within 6 hr after she left the leaflet, or after it was rinsed with a 50% ethanol solution, suggesting that she deposited a marking pheromone on leaflets in the course of the host search and would then discriminate already searched leaflets by recognizing that pheromone. 4) The pheromone appears to be deposited not only on the mine but also on the remaining part of the leaflet. 5) This pheromone would be effective for this species to prevent a waste of time and energy rather than to avoid superparasitism.
