Time-pattern and frequency analyses of sounds produced by irradiated and untreated male Bactrocera tryoni (Diptera: Tephritidae) during mating behavior

Behavior and sounds associated with mating of mass-reared irradiated and untreated (nonirradiated) Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) males were analyzed from synchronous acoustic and video records. The flies tested were from a population used in sterile release programs that help maintain fruit-fly-free areas in Australia. Males typically produce "calling," "courtship," and "copula" sounds as mating progresses. Calling sounds are variable-duration bursts of wing vibrations produced before the male orients toward the female. Rapid bursts of courtship sounds of relatively constant duration are produced after orientation toward the female. Copula sounds of variable amplitude and duration are produced after mounting. There was a significant negative correlation between courtship wingbeat frequency and wing width of untreated males, and those that copulated had a lower frequency than those that failed. Wingbeat frequencies in flight, calling, courtship, and copula sounds were significantly correlated within flies, possibly because they all are produced by the same flight motor, with amplitudes affected by the positioning of the wings relative to "stops" on the thorax. The temporal patterns of calling and courtship sounds differed significantly between irradiated and untreated males. Irradiation is known to damage insect central nervous system interneurons and thereby alter the coordination and timing of behavioral activities, but this is the first study identifying an effect of irradiation on tephritid calling and courtship sounds. Although differences in temporal patterns of calling and courtship sounds have potential to affect mating competitiveness, no differences were observed in proportions of irradiated and untreated males that copulated in the laboratory.