Arthropods harbor various microorganisms in their internal organs. Spider mites and predatory mites possess Wolbachia, which is known to be a causative agent of cytoplasmic incompatibility, parthenogenesis and feminization. Some Wolbachia-infected mites show cytoplasmic incompatibility, which leads to high mortality in fertilized eggs and a low female ratio, but some others do not. Reproductive incompatibility of mites is reviewed with special reference to Wolbachia. Tick symbiotes were first observed many years ago but their phylogenetic affiliations have been unclear. They are closely related to pathogens transmitted by ticks, such as the causativeagents of tularemia, Q fever and spotted fever. Various aspects of the symbiotes are discussed and the importance of further extensive studies on the symbiotes in relation to tick-borne pathogens is stressed.

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A new oribatid mite of the family Damaeidae is described from Hokkaido, north of Japan under the name of Damaeus ainu. This species is related to Damaeus arvernensis Grandjean, 1960 in having a vestigial setad coupled with solenidion on tibiae of legs II-IV and opening of humeral organ in lateral region of the podosoma, but the former is distinguishable from the latter mainly by numerical formulae of setae on epimera and legs.

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Effects of acaricide and fungicide application and optimum timing for control of the ficus mottle mite, Aceria ficus Cotte were investigated in an open fig field in1996 and 1997. Spraying of tebufenpyrad WP, pyridaben WP and thiophanate-methyl WP affected the density of A. ficus on the top part of shoot, but spraying of dicofol EC and oxadixyl?Ecopper oxychlorid WP did not. Spraying of tebufenpyrad WP in the middle of July most effectively retarded the increase in density of A. ficus, and reduced the damage to leaf and fruit.

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The relationship between carpeting period and the appearance of house dust mites(HDM)was investigated in 5 houses in the suburbs of Tokyo. The floors of the investigated rooms were entirely covered with new tile carpets, size 50 by 50 cm. Some of the carpets were removed at 1, 3, 6 and 12 months to examine the HDM and they were replaced by new tile calpets. Although the weight of fine dust from the 1-month carpets varied in each house, the mean weight of fine dust from the 1, 3 and 6-month carpets tended to increase with the carpeting period. The mean numbers of HDM also increased with the carpeting period. A total of 337, 616, 832 and 2, 635 mites/m² was observed for the 1, 3, 6 and 12-month carpets, respectively. Dermatophagoides farinae(Df)or D. pteronyssinus(Dp)dominated most carpets. The dominant rates of Pyroglyphid mites including Df, Dp and unidentified Dermatophagoides ranged from 35.7to100%, while those of the other species were 42.9% or less. It was considered that the HDM fauna dominated by Pyroglyphid mites stabilized after 1-month carpeting and dominating competition between these 2species of Pyroglyphid mites was not related to the carpeting period.

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Mites separated from floor dust in Okinawa Prefecture using sieves with2.0mm or0.5mm-mesh and 0.075mm-mesh were previously reported. We also employed a sieve with0.032mm-mesh to isolate small mites such as Tarsonemid. The mite collections were made from the bedroom floors in3houses(A, B and C)to determine the frequency and number of house dust mites. Among the collected mites, Dermatophagoides pteronyssinus was the predominant mites comprising43.4%of the total number collected, followed by Tarsonemus spp. (23.4%)and Cryptoplophora abscondita(12.1%). To the best of our knowledge, C. abscondita was detected here for the first time in indoor dust. D. pteronyssinus, Cheyletus eruditus, Bak sp., Haplochthonius simplex, Cosmochthonius reticulatus, Cryptoplophora abscondita and Tarsonemid mites were found in all3houses throughout the year. A species belonging to the genus Cosmoglyphus has not been previously reported in house dust in Japan; however, in this study it comprised a considerable number, 22.2%of the total mites collected in May from house C.

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A description of Cosmopirnodus angulatus sp. n. is given. The new species resembles the Vietnamese species, C. tridactylus Mahunka, 1988, but distinguishable from the latter by relatively shorter apodemes, more angular body shape, and shorter setae of notogaster, anal plates and adanal region.

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We experienced two cases of multi-infestation with larval ticks in human. One case was caused by Amblyomma testudinarium larvae and another was by Haemaphysalis longicornis. Only6cases of larval tick infestation have been reported in Japan. We should pay more attention to the important role of larval tick as a vector.

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