In order to obtain the fundamental data for the mosquito control operation, successive studies on the seasonal prevalence of larvae and pupae of mosquitoes were carried out during the whole period of 1962 under the almost same conditions as explained in the previous paper 1962. Stations were divided into three groups as follows : AB group : 8 stations, dominant species is Aedes albopictus (Table 3) CD group : 11 stations, dominant species is Culex pipiens (Table 4) E group : 7 stations, dominant species are Culex tritaeniorhynchus and Anopheles sinensis (Table 5) As a whole, 21, 259 mosquitoes belonging to 3 genera and 6 species were collected (Table 1). C. pipiens occupied 90%, C. vorax occupied 3% of whole collection respectively and other species decreased as compared with the result of the previous paper. Larvae decreased remarkably in number with stages advanced as in the previous paper. C. pipiens decreased considerably from July and on the contrary C. vorax increased in the same period (Table 2). An obvious antagonistic relation has been observed among the above-mentioned two species. Larvae of C. pipiens existed under -3℃〜-6℃ in atmospheric temperature and were observed from April 14 to December 29 in 1962 (Table 4 and 6). C. pipiens was found in all stations except bamboo stumps and other species are going to loose their breeding places in the residential area in Tokyo. C. pipiens is now the most medically important species in suburban area in Tokyo.

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Successful results in preparing chromosome specimens of Culex pipiens complex were obtained by modifying the methods reported for Drosophila and Anopheles. For preparation of the salivary gland chromosomes, 4th instar larvae were dissected in 0.1% solution of sodium oxalate and the glands were isolated from between head and thorax, soaked in freshly prepared fixative for two minutes, stained in 2% orcein solution in the equal amount of the mixture of 85% lactic acid and acetic acid glacial for 3 to 4 minutes, rinsed with the acetic acid and lactic acid mixture, and were squashed under a cover-glass with adequate pressure of a finger. The fixative was prepared by mixing 25 parts of 85% ethanol, 23 parts of 50% acetic acid, one part of 11% formaline and 25 parts of distilled water. Materials of ovaries were prepared by dissecting either 4th instar larvae or pupae at the joint between 6th and 7th abdominal segments, while those used for the study of testes were obtained from pupae since larval testes were immature and too small. Similar techniques as above were applied for the preparation of reproductive organs, but the organs isolated in 0.1% solium oxalate solution were transferred directly into the stain without treating in the fixative.

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Towards making a research of fauna of Acarina on the floors of school buildings during the summer season, a new method was tested. This was done by means of examining the dust collected within vacuum-cleaners by using a mixed solvent (ethyl-ether/chloroform or ethyl-ether/carbon chloride combination). The schools where this new method was tested were : 6 public schools (3 Grade, 2 Junior High, and 1 Senior High) and 3 private girls' schools. The mites collected totalled 6, 766 spp., all belonging to 29 different families (or 20.5 WMI, which means the whole number of mites per one gram of dust). The WMI figure of the mites, as broken down according to schools, is as follows : 66.6-Private Girls' Schools, 7.9-Public (Senior High) School, 4.5-Public (Grade) Schools and 1.9-Public (Junior High) Schools. The numbers of families of the mites are : 23 families in Senior, 20 families in Grade, 19 families in Junior High and 15 families in Private Girls' Schools. The higher the ratio of the number of Acaridiae is, the higher the ratio of the number of active live mites is. The ratio of this particular cohort according to different types of schools is as follows : 98.6% in private Girls', 72.9% in Public Senior High, 47.5% in Grade and 43.1% in Junior High Schools. As for the Oribatids ratio, the above order of schools is reverse. As for Mesostigmatids and Trombidiformids, the orders of schools are as that for the Oribatids ratio, except that Junior High and Grade Schools are reversed. It is considered at this stage of the research that the different floor cleaning methods are contributing factors for the difference in WMI figures and the suborders. It is added that the numbers of mites were the highest for retarded pupils' classrooms and sewing-rooms. No statistic significance of difference was noted in the average WMI among the schools of the same age groups (e.g. among the three Public Grade Schools). The difference was noted, however, between the three grade schools and the two Junior high schools and also between the public and private schools. Both Dermatophagoides farinae Hughes, 1961, and Dermatophagoides scheremetewskyi Bogdanow, 1864 (Epidermotidae), are definitely dominant species on the floors of the school buildings aforementioned. They comprise 89.9% in the Acarina fauna on the floors. It seems that they act as agents for pruritic dermatosis (insect bites) for the reason that there are many reports on the relationship between D. scheremetewskyi and dermatosis. The symptoms of these bites at the above-mentioned schools were seen on the exposed feet and arms of the pupils accompanied by itching red papules each ranging from several millimeters to several ten millimeters in diameter, and no one recognized the agents, although 78% of the pupils in a girls' schools suffered from the bites. This indicates that the agents might have been too small to be visible. Mites other than described heretofore were found as follows : 91 spp. of Cheyletids (1.3%) (percetage of mites total), 87 spp. of Melichares sp. (1.3%), 68 spp. of Acarids (1.0%), 66 spp. of Tetranychids (1.0%), 61 spp. of Hypochthoniids (0.9%), 38 spp. of Glycyphagids (0.6%), 38 spp. of Hypoaspis sp. (0.6%), 33 spp. of Lohmanniids (0.5%), 20 spp. of Tarsonemids (0.3%), 18 spp. of Ornythonyssus bacoti (0.3%), 16 spp. of Pyemotids (0.2%), and others. Meanwhile, as a result of this new testing method, not only the mites but also other arthropods such as Insecta, Araneina, and Cheliferidae were found. Hemiptera, an order of Insecta (larvae of shell worms and jumping plant lice), totalling 120 spp., which was 1.8% of the mites total. 30 spp. of larvae of beetles (0.4%), 21 spp. of book-lice (0.3%) and 16 spp. of thrips (0.2%) were found also. The latest investigation by the Educational Committee of Yokohama shows that 56 out of 216 public schools (26%) have suffered from both rodents and mites

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1. Nine species of mosquitoes which commonly attack the human in the endemic area of filariasis in Amami Island, southern Japan, were experimentally tested for the susceptibility against bancroftian filarial worm. The 3rd stage or infective larvae were examined in four species of mosquitoes; Culex pipiens fatigans, C. tritaeniorhynchus, C. bitaeniorhynchus and Anopheles sinensis. Aedes albopictus, Aed. riversi, Aed. vexans and Armigeres subalbatus were non-susceptible and Aed. Japonicus failed to feed on microfilarial carriers. 2. The majority of ingested microfilariae failed to develop in the early phase, even in C. pipiens fatigans which was shown to be the most efficient host, a large number of microfilariae were lost during the first 36 hours after intake. However, during the same period, only a small part around 4.2% of microfilariae could be found in dejectas. This fact suggests that the loss of ingested microfilariae were mainly due to some processes other than dejection out of the mosquitoes. 3. The rate of infected mosquitoes and the rate of infective mosquitoes increased linearly in accordance with microfilarial density of the donor's blood. The regression line of the former is Y=41.654X+48.735 and that of the latter is Y=25.178X+48.735, where Y is the rate and X is the logarithm of microfilarial density. 4. Host efficiency of C. pipiens fatigans was tested at various densities of microfilaraemiae. Host efficiency of An. sinensis at the density of 1.21 Mf/cmm was 0.076 and that of C. tritaeniorhynchus atthe density of 1.32Mf/cmm was 0.010, whereas, those of C. pipiens fatigans at both densities were 0.75 and 0.67 respectively. This fact shows that C. pipiens fatigans is much more efficient as the host of bancroftian filarial worms than the other two species. 5. Mortality of C. pipiens fatigans increased with the increase of the number of larvae ingested, and it was particularly remarkable when the mosquitoes fed on the blood donor having the microfilarial density over 5.0Mf/cmm. For the most part of the mosquitoes, deaths occurred when the larvae reached to the 3rd stage and started to migrate through the body tissues of the mosquitoes. 6. The indices of the experimental infection were calculated after Kartman (1954) with C. pipiens fatigans at various numbers of intake of microfiariae. The highest ndex was obtained around two to three microfilarial intake per mosquito. Therfore, it was shown that the microfilarial carriers with the microfilarial densityof blood appropriate to serve the above mentioned number of microfilariae to mosquitoes are most dangerous as the reservoirs.

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The differential susceptibility of the sexes of the German cockroach, Blattella germanica L., to the lethal effect of carbaryl was compared by the method estimating the dosage-mortality curves from the individual records that some test insects die from the application of carbaryl while others survive, and the experimental results showed that the female cockroach was about 2.33 times less susceptible to carbaryl than the male.

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Control tests of the diazinon-resistant house flies with Sumithion and DDVP were carried out during September 25 to October 30, 1964, in Mihara area of Hokota Village, Kashima-gun, Ibaraki Prefecture. In late 1960, it was found that a remarkable diazinon-resistance had developed in the houseflies of this area. As residual sprays 0.5% Sumithion・0.2% DDVP emulsion was treated in three areas, while 0.33% DDVP emulsion was treated in one area. In the case of a mixture of Sumithion and DDVP, the fly population estimated by ribbon traps decreased markedly through the period of the experiment. On the other hand, the effect of whole DDVP emulsion was rather unsatisfactory.

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The experiments on the separation of a dieldrinsusceptible and -resistant colony from a field population of Culex pipiens larvae were conducted using seven populations collected in Japan. The separating methods adopted here were as follows : For the separation of the susceptible colony, the larvae from an egg-raft were reared to 3rd or 4th stage, then some of them were tested by the discriminating dosage, in most cases 0.02ppm. The batch of the larvae some of which showed higher mortality were pooled in a bat and the next generation was obtained. This was repeated for three to seven generations. For the separation of the resistant colony, similar method was adopted using the discriminating dosage of 0.3ppm and the discriminating mortality of over 80% to 100%. The usual method of the selection by the pressure of dieldrin was also adopted for this purpose. After the results, the separation of the susceptible colony succeeded in Koniya and Furuichiba populations, and that of resistant colony in Koniya, Furuichiba, Denken and Kawasaki populations. The ld-p lines of the separated colonies showed straight lines and these were in good accord with the estimated ld-p lines by "ld-p line tests" shown by Suzuki et al. (1964). The trial of re-separation of the separated susceptible colony with the discriminating dosage of 0.004ppm ended in failure which proved that the colony obtained here was the most susceptible colony, and more susceptible colony could not exist. The LC-50 of dieldrin to the susceptible and resistant colony obtained here were 0.004-0.006ppm and 0.5-0.8ppm, respectively.

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In order to know the effects of several organophosphorus insecticides against the last instar maggots of the flesh fly, Sarcophaga peregrina Robineau-Desvoidy, an investigation was carried out in the laboratory. Emulsions of eight insecticides, diazinon, malathion, dichlorvos, ronnel, trichlorfon, naled, fenitrothion and trichlorfon were tested through "the dilution contact method" which applies a thin layer of dilutions of insecticides. An explanation of this method will be published elsewhere. It was confirmed that three insecticides, trichlorfon, fenitrothion and dichlorvos, are most excellent in the (LC)_<50> value, and diazinon comes next, the others are in the following sequence, i. e., trichlorfon, ronnel, naled. Malathion may be applicable but it did not show the lethal effect to the maggots so far as these dilution rates are concerned.

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