INFLUENCE OF INTRAPATCH EXPERIENCES AND TEMPERATURE ON THE TIME ALLOCATION OF THE WHITEFLY PARASITOID ENCARSIA-FORMOSA (HYMENOPTERA, APHELINIDAE)

The effect of experiences, such as contact with honeydew, rejections o f hosts, and ovipositions in hosts, and of temperature on the time all ocation of individual Encarsia formosa female parasitoids on tomato le aflets have been studied. Behavioral records were analyzed by means of the proportional hazards model. Analyses were carried out at two leve ls: (1) the tendency of leaving and (2) the tendency of changing from one leaf side to another. The patch-leaving behavior of E. formosa can be described by a stochastic threshold mechanism, which is characteri zed by a certain tendency (probability per time) to leave. The median time from being placed on the leaflet or, if it occurred, from the lat est encounter with a host until leaving was 18.6 min. The median time for changing from one leaf side to the other was initially 11.6 min an d dropped to 5.7 min after both leaf sides had been visited. The effec t of temperature, ranging from 20 to 30-degrees-C, was negligible. The presence of honeydew as well as the first oviposition in an unparasit ized host decreased the tendency to leave, thus increasing the giving up time (GUT) since the latest encounter with a host. Encounters with parasitized hosts did not affect the GUT since latest encounter; as a result, the total residence time increased. After the first ovipositio n in an unparasitized host the tendency of changing from the lower lea f side on which hosts were present to the upper side was decreased. Th e presence of honeydew did not affect the tendency of changing leaf si des.