Foraging Theory as a Model to Examine Parasitism by the Tachinid parasitoid fly Ormia ochracea on the cricket Gryllus rubens

This paper tests the effects of auditory and chemical sensory input on the foraging and larviposition behaviour of an eavesdropping parasitoid fly. Ormia ochracea (Diptera: Tachinidae) use the dominant calling field cricket in their habitat as hosts for their larvae; females locate hosts by eavesdropping on the acoustic calls produced by male crickets. By manipulating directional cues in the auditory stimulus experienced by foraging females their ability to locate hosts and their ability to switch to a novel host following a switch in the location of the stimulus were examined. Success was dependent upon walking behaviour and proximity at stimulus change. After locating potential hosts females must deposit larva and differences in larviposition rates of females, after they had located an attractive sound source (cricket call), in the absence and presence of chemical cues associated with crickets indicate that females may use additional sensory modalities in host-foraging decisions.M.Sc