IMPORTANCE OF ADULT FOOD SOURCES TO HOST SEARCHING OF THE LARVAL PARASITOID MICROPLITIS-CROCEIPES

We conducted field experiments to determine the effects of food availa bility and parasitoid hunger on the searching behavior of Microplitis croceipes (Cresson) (Braconidae; Hymenoptera) in small corn and soybea n plots. In both corn and soybean plots where food was not available, females which were well-fed prior to release parasitized more hosts th an unfed females. Well-fed females spent more time hovering and less t ime searching undamaged leaves than did unfed females. Because hoverin g time is an indicator of active host searching, the better parasitiza tion rate by well-fed females can be explained by the greater proporti on of time spent in active host searching. These results suggest that the lack or shortage of food sources in the field reduces the parasito id's effectiveness. We also found that in a corn plot without food, un fed females more often superparasitized hosts than did well-fed female s. However, when food (honey) was provided in a plot, most unfed femal es found and fed on honey soon after release. After feeding, they quic kly began a hovering search, primarily around damaged plants, apparent ly in search of host larvae. More time was spent hovering by unfed fem ales than by well-fed females in a corn plot with food. In the case of a soybean plot with food, unfed females parasitized more hosts than d id well-fed females. These behaviors suggest that feeding experience o f females in the field may facilitate their host searching around plan ts with food. On the basis of these findings, we suggest that it is po ssible to manipulate the parasitoids' hunger state as a tool for paras itoid release programs. (C) 1995 Academic Press, Inc.