The polymorphic patterns of genomic DNA amplified by RAPD-PCR were detected in laboratory-cultured populations of sweet potato weevils, Cylas formicarius collected from the Southwest islands (Nansei-Shoto) of Japan. When three sets of primers, T13/T13, T05/T05 and T01/T07 were used for PCR, the polymorphic patterns of the amplified DNA were classified into nine types. Of these types, A 1 B 1 C 3 was common in all populations tested. The present study determined the useful primer sets that will enable the successful classification of sweet potato weevils based upon the polymorphic patterns of genomic DNA amplified by RAPD-PCR.

Genetic variations of the internal transcribed spacer-1 region in sweet potato weevil, Cylas formicarius, were examined from 27 collection sites in the main infested areas in the world, except Africa, in this study. The ITS-1 lengths of 36 weevils tested in this study ranged from 557 to 587 bp, and were conspicuously longer in weevils from India. The genetic distances between weevils from India and from the other areas tested were larger than among weevils from the latter areas. The phylogenetic tree based on ITS-1 sequences consisted of two main clades of India and East Asia consisting of Northeast Asia and Southeast Asia subclades. The former subclade was also divided into three minor subclades. Weevils from Georgia and Hawaii (USA), and St. Kitts (the West Indies) belonged to the same subclade as those from Guangdong (China) and Hanoi (Vietnam). Also, weevils from the Ogasawara Islands (Japan) belonged to the same subclade. On the other hand, weevils from the Southwest Islands (Japan) belonged to the same subclade as those from Taiwan. When referring to human historical events, C. formicarius would have gradually spread in southern Asia due to its limited dispersal ability since originating in the Indian subcontinent 90 million years ago. However, after becoming associated with sweet potato, especially after the nineteenth century, local populations with fairly different genetic properties from Indian weevils would have been rapidly spread by human transportation of infested sweet potato throughout the world.

The West Indian sweetpotato weevil Euscepes postfasciatus (Fairmaire) is a major pest of the sweet potato Ipomoea batatas (L.) Lam. and this weevil is a target of an eradication program using the Sterile Insect Technique in Okinawa Prefecture, Japan. Understanding the population ecology is essential in the planning of an eradication program; hence, a host‐plant infestation survey and light trap survey have been conducted to monitor the population dynamics of the weevil on Kume Island (Okinawa Prefecture), which is the target area of the trial weevil eradication project. Seasonal tendencies of weevil density were found in these field surveys, but the tendency found in the host‐plant infestation survey was not seen every year, and the effectiveness of the light trap is somewhat suspect. To confirm the reliability of the tendency observed in these field surveys, the present study attempted to explain the tendency by a seasonal temperature change using a temperature‐based model of weevil population dynamics. The seasonal changes of weevil density differed according to host plants and host‐plant fields. The seasonal changes of weevil density inside the host plant Ipomoea indica and outside the host plants in I. indica fields were consistent with those predicted by the model. However, those inside the host plant Ipomoea pes‐caprae in the host‐plant infestation survey were contrary to the predicted ones, and those observed outside host plants in I. pes‐caprae fields by the light trap survey were not in good agreement with the predicted ones. It was concluded that the seasonal change of the weevil density observed in I. indica and I. indica fields can be explained by a seasonal temperature change, but factors other than seasonal temperature change are needed to explain those in I. pes‐caprae and I. pes‐caprae fields.

To use elytral color morphs of Cylas formicarius as a genetic marker in its eradication using the sterile insect technique, the geographic distribution of the morphs was examined in the three main infested areas of Japan (Central Ryukyus, Southern Ryukyus, and Ogasawara Islands). In addition to the two known color morphs in Japan (bluish elytra (BE) and greenish elytra (GE)), the piceous elytra (PE) was found mainly in the Southern Ryukyus at low frequency. The color morph frequencies varied between the Central and Southern Ryukyus and between locations within the two areas, while only BE was found in the Ogasawara Islands. PE would be useful for genetically marking sterile weevils to be released. Similarly, GE would be useful in some islands where GE is rarely or not found. BE frequencies on two islands in the Central Ryukyus (Amami and Okinawa) and two islands in the Southern Ryukyus (Miyako and Ishigaki) in 2006-2007 were higher than in 2002-2003.

To realize the economical and high performance drive for urban transit, a linear motor is driven as a high performance expensive motor or a economical secondary sheet type linear induction motor (LIM) with relative poor performance which is in practical application, by changing the reaction rail, not changing the primary on vehicle. First, it is discussed the secondary wound type LIM without end effect. It is revealed that the wound type LIM has much larger secondary leakage reactance than sheet type LIM, and the performance is not good in this use. Second, the linear synchronous motor (LSM) is discussed as a high performance motor. It is cleared that LSM realizes both the short primary and high efficiency with unity power factor even in the practical section length for the field excitation. So, authors propose the combination use of LSM in power running or braking region and sheet type LIM in other region.