2008 年 43 巻 4 号 p. 541-545
In 1998, several males of Bactrocera tau, a common pest fruit fly in Asia, were captured on Ishigaki Island, Okinawa, by a trap set for monitoring the melon fly (B. cucurbitae) invasion. In 2003, one male was trapped again. We collected vast amounts of host fruit of B. tau on Ishigaki, but could not confirm infestation by this species. These results indicated that B. tau had invaded Ishigaki at least twice but failed to colonize. B. tau may have come from Taiwan, considering its geographic proximity to Ishigaki and the abundance of the species in Taiwan. The invasions could not be fully explained by natural factors alone; it was possible that human-induced means were also involved. We believe that this species can colonize Okinawa, since the host plants are abundant year-round, a potential competitor, B. cucurbitae, is not currently present, and Okinawa is located south of the northern limit of B. tau. Since B. tau has a host range and population growth capacity similar to B. cucurbitae, the species could cause severe damage to crops in Okinawa, much like that caused by B. cucurbitae in the past. We must remain alert for possible re-invasion by B. tau.
