INDIVIDUAL ENCARSIA-FORMOSA PARASITOIDS WERE OBSERVED CONTINUOUSLY ONEITHER CLEAN, HONEYDEW-CONTAMINATED OR WHITEFLY-INFESTED TOMATO LEAFLETS UNTIL THE PARASITOIDS FLEW AWAY

Individual Encarsia formosa parasitoids were observed continuously on either clean, honeydew-contaminated or whitefly-infested tomato leafle ts until the parasitoids flew away. The residence time on clean leafle ts was about 20 min at 20, 25 and 30 degrees C, and was the same on in fested leaflets when no hosts were encountered. Encounters with unpara sitized and parasitized whitefly larvae, and contact with honeydew pro longed the residence time of the parasitoid on the leaflet. Even when many parasitized black whitefly pupae (unsuitable hosts) were encounte red and rejected, the parasitoid was still arrested on that leaflet. E ncarsia formosa's walking pattern seemed to be random, and parasitoids showed no preference for searching on the upper or lower leaf side wh en no hosts were encountered. There is also no preference for the edge or for the middle of a leaf. Walking and flight activity of the paras itoids was hardly observed at 15 and 18 degrees C. Many parasitoids be came inactive during periods when the barometric pressure decreased bu t did not when it was stable or increasing.