Marking of host fruit by male Rhagoletis boycei Cresson flies (Diptera: Tephritidae) and its effect on egg-laying

Male Rhagoletis boycei flies (Cresson) have been shown previously to guard egg-laying punctures on host walnut (Juglans major) fruit. During their tenure, R. boycei moles were observed to dip the posterior portion of their abdomen repeatedly toward the fruit surface. Closeup video analysis revealed that, during this dipping behavior, a clear viscous substance emanating from the cercus was deposited directly on the fruit. Laboratory assays indicated that the rate of abdomen-dipping was significantly higher on fruit bearing simulated egg-laying punctures than on control fruit and significantly higher in the area of the puncture than elsewhere on the fruit. In a final experiment, the occurrence of abdomen-dipping in the vicinity of a puncture was manipulated independently on separate punctures on the same fruit. On such fruit and in the absence females, previously mated, reproductively mature females attempted oviposition significantly more often in or near a puncture exposed to males than in or near an unexposed control puncture. Possible functions of the putative male-marking behavior from the perspectives of both male and female are discussed.