Analyses of two parasitoids with convergent foraging strategies

We compared the foraging strategies of two key braconid endoparasitoids of the tobacco budworm. (Heliothis virescens Fab.), Cardiochiles nigriceps Vie r. and Microplitis croceipes Cresson, that differ in host and habitat range but otherwise share comparable, overlapping niches. The most important hos t-location cues by far for both species were materials associated with dama ged plants. Both species demonstrated a significant preference for volatile s released from plants damaged by H. virescens larvae over those released f rom undamaged tobacco and cotton plants. In choice experiments with damaged tobacco versus cotton, M. croceipes showed a significant preference for co tton plants. In contrast, C. nigriceps preferred damaged tobacco plants. Pl ant compounds provoked a strong response even when released from systemical ly induced plants (from which damaged leaves, host, and host by-products we re removed). C. nigriceps appears to have a much keener ability to locate h osts over long distances than M. croceipes. This observation may be related to the highly specialized nature of this parasitoid. The possible adaptive significance of the foraging behaviors of these two parasitoids is discuss ed.