Characteristics of heteromorphic deutonymphs of non-psoroptid astigmatid mites were reviewed. The duetonymph was called hypopus since recognized as belonging to the genus“Hypopus”in Mesostigmata, then as one of immature stages in Astigmata. Morphology is far different from the other stages, no functional mouth part, short and stout legs, adapted stmctures for phoresy and so on. Such differences caused taxonomic difficulty in this group. Deutonymphal formation is generally induced by adverse environmental conditions, which it should resist or escape from. Although stimuli to molt to next stage might be different in each species, environmental changes including food supply are necessary for development. The deutonymph, which may represent specific relationships between phoretic hosts exploits other organisms to migrate into new environment. In applied fields, importance of the deutonymph has not been fully understood.

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A new genus, two new species and one new subspecies of the family Ceratozetidae were described from the Tateyama Mountains, Central Japan. They are Cyrtozetes denaliensis minor subsp. nov., Ghilarovizetes maruyamai sp. nov., and Gephyrazetes fasciatus gen. nov. et sp. nov.

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The present paper deals with the members of oribatid mites of the family Phenopelopidae found in Mongolia, which are represented by three new species viz. Eupelops mongolicus spec. nov., Eupelops shagdarsureni spec. nov. and Peloptulus denticuspidatus spec. nov., and one known species Propelops canadensis(Hammer, 1952). Description of new species and redescription of a known species are given in this paper.

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Pseudo-arrhenotoky was investigated by chromosome observation in Phytoseiulus persimilis and Amblyseius womersleyi, both of which have the basic number of chromosomes. To confirm male diploidy at the early stage of embryogenesis, eggs were supplied for chromosome observation immediately after they were deposited. In addition, eggs were collected under two prey conditions, “ ample” and “ poor” and their chromosomes were observed in order to examine the relationship between ploidy and sex. Eggs deposited by the two species showed haploid-diploid sequences corresponding to those of male and female offspring under both “ ample” and “ poor” prey conditions. However, male diploidy and heterochromatinized chromosomes were not observed in the deposited eggs. Therefore, the first eggs expected to be males were extracted from the body cavities of female P. persimilis for chromosome observation. The observation confirmed male diploidy at an earlier stage of embryogenesis which takes place in the female body cavity. The coexistence of haploid and diploid cells in the same egg was also observed at the next stage. However, no heterochromatinized chromosomes were observed at any embryonic stages in the female body cavity, under the present experimental conditions. The present study suggests that pseudo-arrhenotoky occurs at least in P. persimilis with the common number of chromosomes, and that the timing of genome elimination is different from that of the species with an aberrant number of chromosomes.

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Vegetative propagation by herbaceous cuttings is commonly used in chrysanthemum production. Spider mites are also transferred with cuttings from the mother plant. We investigated the vertical distribution of mites on the cuttings of several cultivars and established a control method for mites by dipping the cuttings in acaricide solution prior to planting. Most adult female mites were found between the 4th and 6th unfolded leaves numbered from the apical leaf. Eggs and immatures were mainly found on the 4th and 5th leaves, respectively. Before planting, the cuttings were dipped for 3 min in milbemectin(10 ppm), etoxazole(50 ppm), potassium oleate(3, 000 ppm)or water. Milbemectin and etoxazole prevented mite infestation on chrysanthemums for a month after planting, whereas potassium oleate and water were unable to control the mites and the mite populations increased within 3 weeks. No noticeable developmental damage was observed in the plants after dipping, except that the stem was slightly shortened in one cultivar after dipping into potassium oleate.

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The female of Tarsonemus cornus Ito is described for the first time. It was collected from leaves of bamboo, Phyllostachys pubescens Mazel in Fujian, China.

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In order to study the distribution of oribatid mites as intermediate hosts of horse tapeworm, soil samples were collected from38points of 24 horse pastures in Hidaka. As a result, 18 species belonging to twelve families and1, 848 individuals of oribatid mites were found. The average number of species found in one sample was six. Seven of 12 families, Galumnidae, Scheloribatidae, Achipteriidae, Oribatulidae, Ceratozetidae, Camisiidae and Protoribatidae were widely distributed throughout Hidaka and are considered to be possible intermediate hosts of the horse tapeworm. The active season of oribatid mites is considered to be from summer to fall because a large number of them were found during the season. In the diurnal rhythm, a large number of oribatid mites adhered to the grass on the evening and early morning. Therefore, the highly possible infection time of the tapeworm may be from evening to early morning between summer and fall.

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