Parasitoid foraging and oviposition behavior in the field

Since parasitoids can be reared from their hosts and leave evidence of parasitism after they emerge from hosts, some general outlines of their foraging behavior can be inferred from field studies that do not involve direct observation. However, direct observations are often needed to uncover critical aspects of patch use, host finding, and host use. Studies of parasitoid foraging in the field utilizing direct observation were rare until relatively recently. However, a nascent literature on parasitoid foraging in the field can now be identified that is shedding some light on how parasitoids allocate their time in the field and what they do when they encounter hosts. These studies have been performed on a variety of parasitoids in natural as well as agricultural systems. They range from observations of host-species selection by Drosophila parasitoids foraging in fermenting fruits and sap fluxes in Dutch woodlands to investigations of the amount of time that parasitoids of stem-boring Lepidoptera will wait for their concealed hosts to emerge from within corn plants in the USA, and a number of other interesting studies. In this chapter we review studies of parasitoid behavior in the field, focusing primarily on the implications of these behaviors for density-dependent parasitism and optimal foraging. 3 Parasitoid foraging and oviposition behavior in the field George E. Heimpel and Jérôme Casas