BEHAVIORAL-RESPONSES OF FEMALE ORIENTAL FRUIT-FLIES TO THE ODOR OF PAPAYAS AT 3 RIPENESS STAGES IN A LABORATORY FLIGHT TUNNEL (DIPTERA, TEPHRITIDAE)

Behavioral responses of adult female oriental fruit flies, Dacus dorsalis Hendel, to the odor of papayas from three ripeness classes were studied using a three-choice flight tunnel bioassay. Laboratory-reared flies were allowed to respond freely to any of three papaya odors (mature green, color-break to one-fourth ripe, and one-half to full ripe) emanating from identical (spherical) fruit models. Five behaviors were measured in assessing the fly's relative attraction to the odors (number of landings), arrestment (total fly seconds on sphere), fly-fly interactions on the fruit model (maximum and modal fly density), and acceptance for oviposition (total eggs laid). Females showed no significant difference in total fly landings based on all age classes combined. Significant differences were noted among age classes. Females spent more total time on the sphere and showed a higher maximum density and modal fly density to ripe fruit than to green fruit odors. Ovipositional acceptance of fruit models based on the total number of eggs laid in a sphere was greater in response to the ripe-fruit odor than to the other two odor classes. Olfactory-stimulated behavioral responses of females to the odor of ripe papayas were significantly different from the other ripeness classes for all behaviors at 8 days postemergence and then declined in 11-day-old flies. Behavioral responses were greater during the afternoon than in the morning. Observations of wild oriental fruit flies to papayas in the field indicated a preference for residing on riper fruit. The results of this study are discussed with regard to the role of olfactory inputs generated by the odor of ripening fruit on female attraction and oviposition behavior resulting in infestation of papayas by oriental fruit fly.