Calliphora nigribarbis has a characteristic temperate-zone life cycle. For example, in Japan, they become more active between winter and spring for migration and reproduction [15, 16] . It is well known that C. nigribarbis has excellent flight capacity and high dispersal ability. They have been identified by weather ships at stations located on the Pacific Ocean and East China Sea, 300-450 km from Kyushu Island, Japan [17] . It was also suggested that the number of flies found in autumn in the Kyushu District appears to increase due to their transoceanic migration [18] . Female blow flies can survive for about one year in Japan [17] , in comparison to the house fly Musca domestica which has a mean longevity of 34.2 days [19] . The longevity and high dispersal ability of blow flies may also result in wide dispersion of viruses that they carry. Mark-release-recapture experiments conducted at Tamba Town in 2005 suggested that C. nigribarbis generally could migrate up to 2-3 km in 24 h [20] . The distance between the two poultry farms in Kyoto prefecture, where the two H5N1 virus outbreaks took place in 2004, was approximately 4 km. In fact, 10% of all C. nigribarbis flies collected at a site intermediate between the affected farms expressed H5N1 virus genes [11] . Viable titers of H5N1 influenza virus, but not virus replication, were detected for up to 24 h in the crop and intestine of virus-exposed C. nigribarbis [10] . The presence of infectious virus in blow flies for 24 h could have a strong implication for virus dispersion since blow flies, with their excellent flight capacity, could transport the H5N1 virus over significant distances. In addition, H5N1 virus has been isolated from feces and vomit matter of blow flies at the 48 h postexposure, but virus titers in flies at 48 h were lower than that of the virus-containing cotton used in these experiments. This suggested that the viability of influenza virus decreases steadily in the blow fly crop and intestine, although some infectious virus remains for longer than 24 h. Therefore, C. nigribarbis could transport H5N1 virus to poultry farms 2-3 km apart.