DECISIONS DURING COURTSHIP BY MALE AND FEMALE MEDFLIES (DIPTERA, TEPHRITIDAE): CORRELATED CHANGES IN MALE BEHAVIOR AND FEMALE ACCEPTANCE CRITERIA IN MASS-REARED FLIES

Analyses of more than 300 videotaped courtships of wild and mass-reared medflies from Costa Rica showed that the tendency for male and female to align themselves facing directly toward each other increased, and that the distance between them decreased as courtship proceeded. More direct alignments and shorter distances between the flies at the moment the male jumped onto the female were correlated with greater female acceptance of copulation. There were no consistent differences in durations of components of intermittent buzzing songs or male size between successful and unsuccessful courtship in either strain. Several possible cues may release different courtship responses: males of both strains tend to initiate both continuous vibration and intermittent buzzing after reduction of the distance to the female; slow creeping toward the female was associated with longer courtships that had failed to lure the female close; and females tended to turn to face more directly toward the male soon after the male began continuous vibration, and especially after he began intermittent buzzing. Females became progressively more immobile as courtship progressed, especially soon after intermittent buzzing began. There were numerous differences between strains. Mass-reared males were more likely to mount females without previous courtship than were wild males. Wild males initiated continuous wing vibration when farther from the female and when the female was looking less directly toward them, but the two strains did not differ in the distances and angles at which males initiated intermittent buzzing and jumped. Wild males were more likely to creep toward the female during intermittent buzzing. Mass-reared females but not wild females were more likely to copulate when the proportion of time the male had spent in intermittent buzzing was low, and if the courtship began when the flies were nearer each other. Wild but not mass-reared females were less likely to copulate if courtship was shorter. Possible coevolution of female responses with the five different male courtship traits that differ between mass-reared and wild flies are discussed.