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A lot of sterile males need to be released continuously in the target area in the sterile insect technique SIT . Therefore, mass-rearing of the target pest insects is indispensable for SIT programs. The West Indian sweet potato weevil, Euscepes postfasciatus, has been maintained for over 44 generations 8 years for its eradication program in the Okinawa Prefectural Plant Protection Center Naha, Okinawa, Japan . The selective pressures under mass-rearing conditions are likely to be very different from those of wild ones. The specific selective pressures over many generations under mass-rearing conditions would adversely affect the reproductive capacity of mass-reared insects. Therefore, evaluation of the mating performance of mass-reared males compared with that of wild ones is indispensable in SIT eradication programs. Although we compared mating performance with respect to four reproductive characteristics duration of mating behavior, mating success, mating competitiveness ability and number of transferred sperm in female spermatheca during copulation between mass-reared and wild males in E. postfasciatus, there was no evidence that the mass-reared males were inferior to the wild males in terms of mating performance. Thus, we considered that the mass-rearing procedure for at least 44 generations did not adversely influence the male mating activity in E. postfasciatus.

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The West Indian sweetpotato weevil, Euscepes postfasciatus (Fairmaire), is one of the pests of the sweet potato, Ipomoea batatas, in tropical and subtropical countries. Although an eradication program using the sterile insect technique (SIT) for this weevil is now underway in Japan, the lack of potent attractants such as sex pheromones for this weevil species prevents effective monitoring and hampers pest control operations. New methods to monitor the performance of sterile males using trapped wild females are needed. In this study, we tested whether the ejaculate of the labeled males that were fed an artificial diet labeled with the trace element, rubidium (Rb), is detectable in the fertilized females. We fed an artificial diet treated with Rb (1.00, 0.50, 0.25, and 0.00%) to adult male weevils for 14 d after emerging and quantified the rubidium content in inseminated females. We also examined the side effects of the artificial diet on mating performance and longevity. The advantages of monitoring the spatial level of sterility using data from females labeled with ejaculate of Rb-fed males in an SIT eradication program are discussed.