A survey of the ectoparasites recovered from a total of 135 wild Ursus arctos and 6 wild Ursus thibetanus yielded the following results. Ectoparasitic species : From U. arctos, seven species of ectoparasites were seen : Haemaphysalis japonica, H. flava, H. megaspinosa, Ixodes ovatus, I. persulcatus, Chaetopsylla tuberculaticeps, Trichodectes pinguis. From U. thibetanus, there were four species : H. japonica, H. flava, I. ovatus, T. pinguis. Of the ectoparasites distributed in both Honshu and Hokkaido, those found in both U. arctos and U. thibetanus are H. japonica, H. flava, H, megaspinosa, I. ovatus and T. pinguis. Although I. persulcatus, I. nipponensis and I. longicornis are spread throughout both Honshu and Hokkaido, I. persulcatus is found only in U. arctos, while I. nipponensis and I. longicornis are found only in U. thibetanus. ROGERS et al. (1976) and ЛАБЗИН (1985) , with referral to БРОМЛЕЙ (1965), indicated that U. thibetanus was the host of I. persulcatus, but did not clearly state this. We believe that this is the first reported case of U. arctos playing host to T. pinguis outside of Europe. Regarding the parasitic seasonality of the five species of Ixodidae hosted by Hokkaido U. arctos, there is a suggestion that three species of Haemaphysalis (japonica, flava, megaspinosa) are parasitic the whole year round, while two species of Ixodes (ovarus, persulcatus) are parasitic for the whole year except winter. In Japan, T. pinguis is hosted by U. arctos and U. thibetanus, and distributed throughout Hokkaido, Honshu and Kyushu. C. tuberculaticeps hosted by U. arctos is distributed widely in Hokkaido and are parasitic in U. arctos at least between April and October. Comparing gender, three species of Haemaphysalis (japonica, flava, megaspinosa) have a higher incidence in males. On the other hand, two species of Ixodes (ovatus, persulcatus), T. pinguis and C. tuberculaticeps have a higher incidence in females. Among the five species of Ixodidae hosted by U. arctos, copulative pairs were collected from all species except H. flava (H. japonica, H. megaspinosa, I. ovatus, I. persulcatus). These species are using the host as a place for propagation. Life stage : Only adult I. ovatus and C. tuberculaticeps were collected from the host. Adults, nymphs and larvae of three species of Haemaphysalis (japonica, flava, megaspinosa) were collected. Larvae were identified only to genus level. Adult and nymph I. persulcatus and T pinguis were collected. Habitat : Parasites were found every on part of the host body except the paws. In the case of U. arctos and Ixodidae, the maximum ratio of distribution was on the head (47.8 %), then on the back below the neck (29.9 %), axilla and belly (12.4 %) and legs (9.8 %). Host U. thibetanus and parasite C. tuberculaticeps had a similar tendency. Maximum number of parasites : The U. arctos captured in June had four species of Ixodidae, for a total of 670. Mixed infestation : Mixed infestation was seen all year round. The percentage of mixed infestations in positive hosts was 66.7 %. The maximum mixed infestation totalled five species. Prevalence : In U. arctos in Hokkaido, H. japonica had the highest prevalence (54.1 %). Next highest was I. ovatus (50.4 %), I. persulcatus (28.9 %), H. megaspinosa (27.4 %), H. flava (19.3 %), C. tuberculaticeps (2.2 %) and T. pinguis (0.7 %). By dividing the U. arctos habitat of Hokkaido into ten areas, each parasite was most prevalent in the following areas : H. japonica in Yubari= Hidaka and Akan=Shiranuka, H. flava in Oshima, H. megaspinosa in Yubari=Hidaka, I. ovatus in Oshima and Yubari=Hidaka, I. persulcatus in Yubari=Hidaka, Akan=Shiranuka and Shiretoko. However, H. flava, H. megaspinosa and I. persulcatus had a low prevalence especially in the Daisetsu=Monbetsu area. Five species of Ixodidae also had a low prevalence in the northern part of Hokkaido.
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