RESPONSE OF THE MELON-FLY PARASITOID PYSTTALIA-FLETCHERI (HYMENOPTERA, BRACONIDAE) TO HOST-HABITAT STIMULI

Cohorts of mass-reared adult female Pysttalia fletcheri, parasitoids o f the melon fly (Bactrocera cucurbitae), were exposed to host-plant st imuli in a laminar airflow wind tunnel to analyze the cues used in hos t-habitat finding. Parasitoids hovered twice as frequently around plas tic zucchini models emitting fresh cucumber odor as around models emit ting clean air. The odor of decaying pumpkin was even more attractive, resulting in over a 10-fold increase in hovering, a 50-fold increase in landing, and a 150-fold increase in host-searching and probing beha viors compared to clean air. Fresh cucumber leaf odors were not attrac tive to the parasitoids, but decomposing leaves elicited a strong incr ease in hovering, landing, and searching behaviors. Plastic leaves whi ch visually simulated cucurbit foliage did not in themselves significa ntly alter orientation behaviors, but the combination of leaf visual s timuli plus decaying leaf odors caused strong increases in hovering, l anding, and searching. Fresh pumpkin odor and the odor of yeast-inocul ated pumpkin were not as attractive to parasitoids as decaying leaf od ors. Yeast isolated from decaying pumpkin and cultured on various ster ile media were not substantially more attractive than clean air.