Seasonal and spatial distributions in relation to reproduction of blowflies (Diptera, Calliphoridae) in Hokkaido, Japan

Abstract

Seasonal and spatial distributions of blowflies in relation to reproduction were investigated by baited traps in eight sites from lowland to high mountainous areas in Hokkaido, Japan. A total of 6,571 blowflies consisting of seven species in three genera was collected. The most predominant species was Calliphora vomitoria (Linnaeus) (5,946 flies, 90.5%), followed by C. nigribarbis Vollenhoven (537 flies, 8.2%). The remaining five species (Triceratopyga calliphoroides Rohdendorf, C. vicina Robineau-Desvoidy, C. loewi Enderlein, C. subalpina (Ringdahl), and Aldrichina grahami (Aldrich) were few in numbers. Calliphora vomitoria had the highest peak in autumn (October) in lowland to upland areas (70 m, 400 m, and 500 m), and it was also abundant from July to September in highlands (1,000-1,150 m). Calliphora nigribarbis was present in low numbers, but it was comparatively abundant in summer in highland areas (1,000-1,150 m). Emergence traps yielded 1,441 individuals from four species (C. vomitoria, C. nigribarbis, C. vicina, and T. calliphoroides), showing their reproductive potential in each site. Of these, C. vomitoria and C. nigribarbis emerged at 500 m (Nissho Pass) and 1,850 m (Mt. Kurodake) in August, indicating that they have reproductive cycles at upland to high mountainous areas. Further, adult emergence of C. vomitoria in 2009 from traps placed in the preceding autumn at Mt. Kurodake showed that this species can hibernate at high altitudes. For C. vomitoria, 62.7-84.1% of females had matured follicles (stages IV-V), and mating rates were very high (99.5-100%) in lowland and uplands in October. At Mt. Kurodake, high percentages of females of C. vomitoria and C. nigribarbis had mature follicles from July to October, with high mating rates. Life histories and reproduction of blowflies in Hokkaido were discussed.