Evidence for a male-produced sex pheromone and behavioural responses of the Oriental fruit fly, Bactrocera dorsalis (Hendel) to the pheromone in a horizontal wind tunnel

Evidence for a male-produced sex pheromone and behavioural responses of male and female Bactrocera dorsalis to the pheromone were investigated using a horizontal wind tunnel under laboratory conditions. Responses of males and females to different combinations of live flies and male rectal glands were assessed by monitoring three behavioural parameters namely the number of flies performing upwind straight and zigzagging anemotactic flights over at least 50cm to the treatment, total number of flies landing on the treatment and the total number of flies moved into the upwind section of the wind tunnel after 20 minutes. Significantly high female responses to live males were recorded in all three parameters considered. Male responses to either males or females were considerably low. It is evident from the results that female B. dorsalis are attracted to males and not vice versa. Neither of the sexes was attracted by their own sex and the lack of responses of virgin males to virgin females can be considered to be strong evidence for the absence of any female odour attracting males. Female responses to male rectal glands were at their highest during the „dusk‟ period. Behavioral responses of females observed in the wind tunnel allow the conclusion to be drawn that the source of production or storage of the sex pheromone in B. dorsalis males is the rectal gland. In addition, these results confirm the previously reported observations that mating activity in this species occurs only during the dusk period.Key words: Bactrocera dorsalis, behavioral responses, male-produced sex pheromone, rectal glands, wind tunne