A taxonomic and morphological observation was done on the specimens of myobiid mites collected from laboratory mice suffering from skin lesions. These mites composed of Myobia musculi and Radfordia affinis were described of their four stages in life history, and the comparison in chaetotaxy of dorsum and legs was made between each species and stages.

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Since the Kii-type of the Trombiculid mite, T. mitamurai, the distribution of which has hitherto been considered to be isolated in the southern part of the Kii Peninsula, was collected in the basin along Gokase River of Miyazaki Prefecture in 1959, the authors have made a study on specimens of T. mitamurai collected in this prefecture in the past several years and found that the both types, Kii-type as well as Hiroshima-type, are distributed in several places. According to the results of collection, the majority of the Kii-type have been recovered from Urotrichus talpoides and in comparison with the Hiroshima-type the scope of the host appears to be narrow. Also, the Kii-type was collected from forest but not from field and residential section. As compared with the Kii-type obtained in Kii, no difference was obtained generally in sizes of scutum. Some consideration has been made on the distribution of the Kii-type in Miyazaki Prefecture, but a satisfactory explanation on the geographical distribution, variation and so on will depend a great deal upon the future studies.

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During the period from May to November, 1957, the writer investigated twenty-four times on thirty stumps of bamboo (Phyllostachys bambusoides Sieb. et Zucc.) in a bamboo grove in Utsunomiya City. 1. The mosquito larvae collected were of only two species : Aedes flavopictus (85.3%) and Aedes albopictus (14.7%). 2. Ae. flavopictus always appeared dominant and reached their maximum number at the end of August. Ae. albopictus reached their maximum number in the middle and end of August. The former disappeared at the end of October, while the latter at the biginning of the same month. 3. In the bamboo stumps there were formed only three kinds of larval associations : Ae. flavopictus association (73.7%), Ae. flavopictus-Ae. albopictus association (15.8%) and Ae. alvopictus association (10.5%). 4. There was not seen the phenomenon of "habitat segregation" between Ae. flavopictus and Ae. albopictus in the bamboo stumps. 5. Compared with larval fauna of the mosquitoes in the stumps of another kind of bamboo (Mosochiku) formerly reported by the writer, in the present case the results were very poor, i. e. much smaller in number of species and individuals.

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Since 1950 the author has been engaged in the research of insecticide resistance developed in the insects of medical importance in Japan. This report dealt with the main points of the author's observations and findings.

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Males, females and larvae of certain stage of German and American cockroaches were brought into contact with filter paper treated by 5% lindane, 5% chlordane and 5% dieldrin xylene solution at rate of 50cc per m^2, and the knokdown percentage of the roaches was recorded. After the results, younger stage of the larvae was more susceptible than that of the older ones, though the adult of males gave higher knockdown percentages than the old or last instar larvae. The susceptibility of German and American roaches of the same body weight was nearly in the same level to lindane or dieldrin. To chlordane German roaches were more tolerant than American ones. With the ten-fold increase of the body weight in the larval German and American roaches, the LT-50's increase 2.5 and 2.5 times with lindane, 1.9 and 2.0 times with chlordane and 2.0 and 4.0 times with dieldrin, respectively.

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In order to know the contact toxicity of various insecticides against caterpillars of the Far Eastern urticating moth, Euproctis flava Bremer, a study was carried out in the laboratory. Six insecticides, γ-BHC (lindane), tech.-DDT, dieldrin, diazinon, DDVP and allethrin were tested through topical application method using a tubelculin syring. It was confirmed that the two organophosphorus insecticides were more effective than all the others, and allethrin was next. Dieldrin showed nearly equivalent effectiveness as γ-BAC. It was farther confirmed by using micrometer syringe that the γ-BHC is superior to DDT, and the LD-50 value of tec.-DDT is about five times to LD-50 of γ-BHC, when those were tested against the last instar caterpillars. In an incidental test, the toxic effect of Lead arsenate used as stomach poison was preliminarily estimated.

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The effect of Dibrom, or dimethyl 1, 2-dibromo-2, 2-dichloroethyl phosphate, to house flies was compared with DDVP and diazinon by laboratory and field tests. The LD-50 of Dibrom to Takatsuki strain of house flies was 0.023_γ per female fly, thus showing more effective than DDVP or diazinon which gave the LD-50's of 0.034_γ and 0.072_γ, respectively. After the results of knockdown tests by several methods, Dibrom gave the most rapid effect under open conditions, while DDVP gave the most rapid one under closed conditions, perhaps by reason of higher volatility of DDVP. In residual effect, DDVP was the lowest, and Dibrom was in the same level with or rather superior to diazinon. After the field tests, the residual spray of Dibrom was effective so long as 15 days to house flies.

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A field control test of adult and larval flies by the application of Nankor, or O, O-dimethyl 0-2, 4, 5-trichlorophenyl phosphorothioate, was carried out from August to September, 1960. Either 0.5% kerosene solution of Nankor was sprayed on the ceiling and walls of dwellings and cattle sheds, or 1% solution was applied as aerosol. This was repeted at intervals of 10, 14 or 20 days. On the other hand, 0.025% Nankor emulsion was sprayed on the floors of cattle sheds at rate of 1l/m^2, and in the latrins 2l/m^2, both once a week. As the synerthetic effect of these treatment, the population of house flies remarkably decreased from 15 to 20 days after the first application. This was more remarkable in cattle sheds than in human dwellings. The decrease was suposed to be attributed mainly to the effect of larvicide applied on the floors of cattle sheds. To the lavae in latrins, the application of 0.025 to 0.05% Nankor emulsion at rate of 1l/m^2 once a week was effective. However, as the larvae reappear after 4 to 7 days, the application should be repeted at intervals of 7 or 10 days for practical control.

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Field test of aerial application of dipterex was made for flies and mosquitoes of sanitary importance in rural area of Takasago city, Japan. Three kilogram of 4 per cent concentrate of dipterex in dust per hectare were applicated by Bell 47 G helicopter. In the result, remarkable reduction was observed even in the dwelling species of Musca domestica vicina and Fannia canicularis. Temporary but remarkable reduction was observed on the adults of the mosquitoes of Culex and Anopheles, and also, on the larvae of the same genera in open breeding sites.

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From March 1955 to January 1956, surveys of trombiculid mites at six points, each eleven times, covering five areas in Okayama districts were carried out. Total number of the mites taken from 40 rodents of 6 species were 2, 851. About 88% of them were Trombicula fuji which might be the dominant species in the districts. Others were T. kitasatoi, Gahrliepia saduski, T. murotoensis, T. kochiensis, T. kuroshio, T. miyajimai, T. daisen (?) and T. tanaka-ryoi.

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