1) In the present study, a newly devised ethyl ether/carbon-tetrachloride mixed solvent floatation-fractionation method was developed for the extraction of the mites in the house-dust, and the extractive efficiency of this method was estimated. The most extractive fraction was IV (1.5>specific gravity≧1.45), and the accumulative composition from I to V was 96.8% in number of the mites. According to the divergency of the mite fauna, however, the most extractive fraction varied from II to V. Of all mites extracted, live mites with the appearence of complete shape was composed of 11.3%. The problems of the extraction method of the house-dust were raised comparing the present method with Spieksm's method. 2) The mite fauna of the house-dust, collected from eight districts of Japan and one of Taiwan, were examined. The entire mites number collected from nine samples of one-gramme unit material was in total 9, 489, for one unit sample, 1, 054.3 in average varying from 435 to 2, 050. The mites belonging to Pyroglyphidae Cunliffe, 1958 were classified into five species, Mealia pteronyssina, M. passericola, M. farinae, Euroglyphus maynei and Malayoglyphus intermedius, and were not only present in all samples but the largest in composition, 43.5% in average. The glycyphagid mites, Glycyphagus privatus, Chortoglyphus arcuatus and Blomia sp., were dominant in three samples, respectively. As a whole, more than 36 species of the mites referable to 17 families were distinguished. Of all of them, some were considered indigenous species as characteristic house-dust dwellers or their predators, another were considered incidental intruders. 3) With some Numerical Taxonomic Methods, these nine mite fauna were compared and classified. It was recognized a relationship in the similarities among the mite fauna, and it could be evaluated and classified by that Methods. 4) The significance of the mites and their excrements in the house-dust as the inhalant allergen to the house-dust sensitive patients with brochial asthma was discussed. The cross- and specific antigenicity of the mites, which are seen in the clinical studies, were accounted for in connection with the mite fauna of the house-dust.

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The gonotrophic dissociation in Culex tritaeniorhynchus was commonly observed when mosquitose were exposed to out-door conditions in autumn through early winter, even if the larvae were maintained at high temperature and long day. The ratio of the gonotrophic dissociation in mosquitoes experienced out-door conditions from the pupal stage increased in accordance with the advance of the seasons. Mosquitoes transferred to the out-door after the emergence into adults showed neither the high ratio nor the seasonal elevation of the gonotrophic dissociation. Four types of the follicle development were designated by the observation : the complete absence of the follicle development (complete gonotrophic dissociation), the suppression of the follicle maturation (incomplete gonotrophic dissociation), the maturation of one or a few number of follicles (incomplete gonotrophic concordance) and the complete maturation of a number of follicles (complete gonotrophic concordance). The temperature at the time of pupal stage was not linearly correlated with the ratio of the gonotrophic dissociation indicating that other factors are relating on the appearence of the phenomenon. The photoperiod was considered to be the most regulative factor other than the temperature.

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The majority of resting C. p. fatigan adult do not move much in daytime, but it becomes restless during 18.00-19.00 hr. The density in morning and afternoon, as well as the density in daytime and 19.00-22.00 hr. were similar values. However, no correlation was found in the number caught in each house in daytime and 19.00-22.00 hr., though it correlated between morning and afternoon. Number of occupants, construction type of houses and size of house could not be correlated significantly with the resting density. The distance of the houses from the breeding site was significantly related to the number of resting mosquitoes, as more resting ones were collected at the short distance houses from the breeding places. Observations on resting showed that 44.1-60.3% of mosquitoes were on hangings. Then 58.9-63.9% of the detected population were collected using a sucking tube in 5 minutes. Three different periods of spending time per house, 5, 10 and 15 minutes, do not give significant difference in the density. One hour catch can give 2.6 to 4.8 times of mosquitoes of 5 minutes collection. Removal method to estimate the absolute population in a house was tested. Total estimated was about 3 times of the first 5 minutes catch. By comparison of the biting and resting catch, it is found that the number caught at each house by resting collection does not correspond to the number biting in the house. However there is a relationship between the resting density of an area and the biting density there. A comparison between random sampled houses and total houses examination was made. There is no significant difference regarding the density, but not enough female adults to determine filaria infection rate were available from the random collection. Therefore, 100 houses were selected, to that sufficient adults could be obtained to dissect, although this catch is not a true measurement of the overall density of the population of C. p. fatigans of the area. Rough resting density was indicated through the study of negative house ratio and male proportion in an area.

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Field tests were made to evaluate the effects of the wide application of tabletized or granulated baits compounded in the same way as previously reported (Tsuji and Ono 1969) on field populations of the German cockroach at 5 stations. Population surveys at 4 stations gave the following results. 1) Considerable increases in mortality of cockroaches were produced by the bait treatments, while the bait removal tried at a station gradually decreased the mortality. 2) After the bait treatments, populations markedly declined within 2 weeks at 3 stations, and within 3 weeks at another. 3) The proportion of nymphs to total cockroaches was always exceptionally large in rapidly growing populations, and the bait treatments had no common effect on the age distribution in all populations. The bait treatment was effective in controlling the German cockroach also at another station where no trap survey was made. Further improvements of the baits seem to prepare one of the hopeful approaches to cockroach control in future.

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Study on the relations between diazinon-resistance and esterase activity in Culex pipiens pallens larvae was carried out by the thin layer electrophoresis developed by Ogita. Esterase activity of the 4th instar larvae revealed by β-naphthylacetate hydrolysis was separated into 4 bands. Diazinon-resistant colonies showed marked higher E_2 and E_3 esterase activities than susceptible strain. The E_2 or E_3 esterase has an ability to hydrolyse phenylacetate and methyl-n-butyrate, but not acetylcholine.

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In order to observe some ecological habits on seasonal oviposition and ovarian development of Culex tritaeniorhynchus summorosus, laboratory surveys and experiments were made with wild-caught engorged mosquitos which were collected every month by a light-trap in a pigpen in the suburb of Yokohama during the periods from June to September 1968 and 1969. The survey on the seasonal oviposition was performed with adult females isolated individually in glass pots, 8cm high and 9cm in diameter, while 30-50 females were kept in a cage of 30cm cube as a control of the single rearing. The mosquitos were reared under uncontrolled climatic conditions and divided into two lots of the sugar water supply with respective concentrations of 0.5 and 5.0%. The sugar solution was renewed every day or on alternative days. In the single rearing it was found that in the mosquitos given 5% sugar solution only 60-70% of those oviposited by the 7th day after rearing in June and July as compared with about 90% in the 0.5% sugar lot. It was accordingly obvious that ovipositing activities in the former were more delayed than those of the latter. In August and September, however, there was no significant difference between the two lots in their ovipositing processes and, especially in September, all the females laid rafts during the shortest period within 8-11 days after rearing. On the contrary, in the cases of mass rearing in cages, ovipositing activities were very much delayed even in the mosquitos fed on 0.5% sugar solution compared with those of the single rearing. Also in the cases of single rearing, the oviposition rates of lots given 0.5% and 5% sugar solutions were calculated as 94.2% and 96.2% respectively on the averages throughout the seasons from June to September. The average egg numbers per raft of primipars were counted as 233.3 eggs for the 0.5% sugar lot and 239.3 eggs for the 5% one respectively. Since these differences were not significant, it was suggested that sugar solution did not affect the oviposition and egg formation of mosquitos engorged. Twenty five per cent of the females retained eggs after the oviposition without any relation to the sugar concentration and, in some cases, "separate oviposition" could be seen in the females which had a great number of retaining eggs after their first and incomplete oviposition, i.e. these mosquitos laid rafts twice or thrice up to the complete oviposition of all their retaining eggs. Including laboratory oviposition, biparous or multiparous females of the wild-caught mosquitos increased seasonally, being the rates 3.2%, 6.1%, 40.5% and 64.4% in respective month of June through September. The survey on the ovarian development after feeding on mice were performed using F_1 females reared in the laboratory from rafts obtained from the wild-caught mosquitos. The gonotrophic dissociation appeared in almost the same patterns from the former report (Harada et al., 1968) and, regardless to the sugar concentration, 70-80% of the females emerged in late August or early September failed to develop their ovaries after the blood meal. It was reconfirmed consequently that, in nature, the larvae which will give rise to hibernating females start their life at a day length of 13 hr or less in Yokohama area. In the adult females which were put continuously in an insectary (28-30℃) from the pupal stage, however, only about 17% failed to develop their ovaries even under the short photoperiod of 12 hours owing probably to the high temperatures during the pupal and adult stages.

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A series of field investigations were carried out during the summer of 1967 in a village in Okayama Prefecture on the resting behavior of the adult mosquitoes of Culex tritaeniorhynchus summorosus Dyar, 1920, the principal vector of Japanese encephalitis in Japan. A special type of cubic mosquito net traps (exactly 1.5 meters square in size) were constructed by covering the top and the side walls of frame works with white cloth, with the bottom left open. The traps were set at different times of a day on various types of possible resting places, such as thickets near pigsties, sweet potato fields and rice paddies. A large sucking tube connected with a vacuum sweeper operated by a portable electric generator (Honda Super-watt-300) was used for catching the adult mosquitos from inside of the mosquito net trap, and the population density per 1.5m^2 as well as their composition at certain times of a day in certain resting places was recorded. Laboratory and field studies with other methods were carried out also to supplement the information necessary for estimating the daily rhythm of their activities. As a result, it has been shown that the adults of this species of mosquito are nocturnal in activity as the principle, and take various types of vegetations as their daytime resting places, especially under low and flat leaves of densely growing plants, such as in sweet potato and strawberry fields. The adults were found to emerge from pupae at night with a peak at about the midnight, and the newly emerged males and females mostly stayed on nearby plants at least until the next morning. The mating was estimated to take place on the second night, the blood sucking of females in or after the third night, and the first oviposition during the sixth or the following nights. The females successfully engorged with blood were found to be resting during the night on nearby thickets, but moved to more suitable daytime resting places at dawn such as under leaves of thickly vegetated sweet potato fields. Large numbers of both males and females (including all gonotrophic stages) were found to be resting during the daytime in such a type of vegetations, but most of them flew away into the air after the sunset.

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An ecological study was made on the larval population of mosquitoes in Nagoya district, central part of Japan, from July to November in 1967. The purpose of this report is to elucidate population dynamics of important species in a paddy field and irrigation ponds from the view point of seasonal change of population size and larval age structure, and to estimate relative abundance of newly emerged adults at population level. 1) The number of larvae and pupae sampled from a paddy field was 5, 238, of which 83% were Culex tritaeniorhychus, 16% Anopheles sinensis and the rest were Culex orientalis, Culex vishnui and Culex pipiens pallens in descending order of abundance (Table 1). In irrigation ponds, 19, 024 individuals were caught ; nearly all of which (97%) were C. tritaeniorhynchus and the rest were C. pipiens pallens, A. sinensis and C. vishnui in descending order (Table 2). 2) In the paddy field, the larval population of C. tritaeniorhynchus was observed from July to September, and the population size reached its peak at the middle of July (Table 1). The change of larval age structure had been analyzed, and adult emergence at population level was thought to occur at least four times, of which the first one (early to middle July) was estimated to be the largest on the basis of the foregoing abundance of the fourth instar larvae and pupae (Fig. 3). In the irrigation ponds, the larval population of the same species was observed from the last part of June to the first part of October and a sharp peak of the population size appeared later in July (Table 2). During the period, adult emergence at population level was recognized four times, of which the second one (middle to later July) was the largest (Fig. 4). 3) The larval population of A. sinensis was observed from July to the middle of October, and a peak of population size appeared later in July (Table 1). During the season, adult emergence at population level occurred five times, of which the first one (early to middle July) was the largest (Fig. 3).

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A description was presented of two kinds of artificial devices which were found useful in feeding for biting midges and mosquitoes on blood and virus suspensions. 1) A feeder invented for Culicoides puncticollis was a dome-shaped cage made of nylon cloth attached to the edge of a celluloid ring 8.5cm in diameter. The bottom of the ring was covered with a piece of gauze. A group of biting midges which was introduced in this cage fed with a highly engorged ratio through the gauze which had been put upon absorbent cotton impregnated with some blood containing sucrose and African horse-sickness virus suspension. 2) A device invented for mosquitoes was composed of a cage and a tube introducing circulating warm water for the maintenance of temperature. A membrane derived from the crop of a chicken covered the surface of the tube. The cavity between the tube and the membrane was filled with liquid for feeding. Blood containing Japanese encephalitis virus virus was fed efficiently by females of Culex tritaeniorhynchus summorosus through the membrane having a wide surface area than those of the streched membrane types.

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Twenty arthropod species found in nests of the Japanese house martin, Delichon urbica, were presented in Table 2. Among these, blood-sucking ectoparasites, free-living Psocoptera and nidicolous mite, Dermatophagoides passericola, were abundant. The fauna also contained predatory species such as cheyletid and bdellid mites in considerable numbers. Further nest examinations will add to the fauna numerous species including parasites on the birds and other arthropods which may be carried accidentally either by the birds or with nest materials. Because of the close association of the nest sites to houses, some arthropods have been reported to creep into the room and at times regarded as nuisant pests. In this respect, moderate sized species such as fleas, hippoboscid fly and argasid tick have already been incriminated. However, medical significance of Psocoptera, blood-sucking and nidicolous mites occasionally found in the nests have so far been ignored, since they are scarcely noticed. The fairly durable nests of D. urbica are used repeatedly during the successive breeding seasons. This may furnish the nest dwelling arthropods with favorable external conditions to propagate themselves. It is recommended to remove the nests built on houses during the overwintering season of the birds for depopulating the remaining arthropods. Insecticides may be applied additionlly on the cleared nest sites.

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In order to analyze molar wear for age determination, the albinos, Rattus norvegicus albinus, have been reared in small cages with rats-mice crackers and some vegetables for two years since May 1966. Fifty five of them (♂21, ♀34) which were 1 to 24 months old were used successively in this study. The anterior crown height of the lower first molar was measured tentatively and it was found that the crown height decreased in inverse proportion to age in months, but there was too large deviation in each age group to be used for age determination. On the contrary, there was a large correlation between wear-area of one upper molar (Y__-, in square mm) and log of age in months (X__-), showing the coefficients 0.946 for males and 0.963 for females respectively. Regression lines of Y__- on X__- were as follows : male Y__-=4.61X__-+1.68 female Y__-=3.98X__-+1.57 It must be considered, however, that the deviation was larger in old rats than in young one, e.g. wear-area (within the (mm^2) rat age in months range of S. E.) 2.5 1.1-2.0 male 2.5 1.3-2.2 female 6.5 8.4-14.8 male 6.5 13.6-22.2 female

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A new synergistic substance named Tropital was studied with three pyrethroids to the Takatsuki strain of the housefly, Musca domestica vicina Macqu. Tropital showed the practical synergistic activity for pyrethrins but the degree of increase in toxicity was not so remarkable as in the case of piperonyl butoxide.

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