Abstract
Since the eradication of the melon fly, Dacus cucurbitae COQUILLETT, on Kume Is. (6, 247ha), Okinawa, Japan, in 1977 the melon fly has been detected on 4 instances up to 1982, in spite of the release of sterile flies on Kume Is. (ca. 6×106 sterile pupae/month) and on the adjacent islets (total surface: 4, 764ha, ca. 6×106 sterile pupae/month) located between Kume Is. and Okinawa Is. where the fly population is high. Flies were detected from the autumn to winter and they were again eradicated until the next spring in increasing the number of sterile pupae released on Kume Is. by ca. 2×107/month. Analyses of data on trapping and host fruit inspection suggested that the appearance of these flies on Kume Is. was associated with the invasion of adult flies from the adjacent islets where the flies seemed to reach a high density level of population in summer. The decrease in the effective number of sterile adults on Kume Is. associated with the poor conditions of the pupae released was also held responsible for the reproduction of the flies. In the summer of 1982, the number of sterile pupae released on the adjacent islets increased by ca. 1.5×107/month and the method of release on Kume Is. was improved. As a result, no melon fly was detected on Kume Is. during 1982.
