[in Japanese]

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Successive studies on the seasonal prevalences of mosquitoes were carried out during the period of three years from 1954 to 1956 at two or four places in Yonago City using light trap and at a place using exhauster in 1954 especially, and following results were obtained. 1. Number of mosquitoes collected were 4 genera, 12 species, 8, 793 individuals in 1954, 4 genera, 13 species, 16, 514 individuals in 1955, and 3 genera, 11 species, 4, 684 individuals in 1956 respectively. Culex pipiens, C. tritaeniorhynchus, and Anopheles sinensis occupied the great majority of the specimens (approximately 96 to 98% each year). C. pipiens decreased number of specimens collected from 1954 to 1956, i. e. 75, 56, and 19% respectively, while C. tritaeniorhynchus increased percentage gradually (11, 28, and 75%) and became top of the species in 1956. 2. The tendency of decreasing number of individuals was observed in 1956 than 1955, especially C. pipiens decreased remarkably. And number of C. tritaeniorhynchus collected at Nishi Machi also decreased to approximately half of individuals in 1955. These phenomena may be caused by artificial changes of habitats, such as spray of insecticides, etc. 3. The male of C. pipiens collected always more than the female and A. sinensis showed almost similar tendency, but no such fact was observed in C. tritaeniorhynchus. 4. The seasonal prevalences of the species mentioned above were as follows : C. pipiens : First collection of female and male were in the middle of March and at the beginning of May respectively and ended in the middle or the end of November. The peak of population curve was observed from the middle of June to the beginning of July. C. tritaeniorhynchus : Appeared in the middle of June or at the beginning of July, came to the peak at the end of July or the beginning of August, and ended at the end of October. A. sinensis : Appeared at the beginning or in the middle of June, became peak in the middle of July to the end of August, and ended at the end of October. 5. The patients of Japanese B encephalitis appeared 10 to 30 days after the peak of C. tritaeniorhynchus.

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1) The observation on the seasonal prevalence of mosquitoes has been made at a cow barn in Kamo City, Niigata Prefecture, from March 1956 to May 1957 with the exception of winter season. 2) This collection has been made two or three times in each 10 days during the period using an insect net, and the total number of mosquitoes obtained was 3, 366, consisting of 52.5% Aedes vexans nipponii, 26.6% Anopheles sinensis, 11.6% An. sineroides, 6.8% Culex tritaeniorhynchus, 2.2% C. pipiens pallens, 0.3% Armigeres subalbatus, and 0.0% Aedes albopictus (Table 1). 3) Each of these species had their own seasonal prevalence as shown in Fig. 1 and 2. An. sinensis and An. sineroides appeared early in April and could not collect at the end of November. An. sinensis exhibited two definite peaks in occurrence, on the contrary An. sineroides showed nearly three peaks. Ae. vexans nipponii appeared in the middle of May, and disappeared in the middle of October, exhibiting two distinct peaks, the highest one was formed early in June. C. tritaeniorhynchus and C. pipiens pallens appeared early in July and disappeared late in September. 4) C. tritaeniorhynchus showed a small peak in occurrence early in August, on the contrary C. pipiens pallens did not show any peak.

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Observations were made on the attracting effect of carbon dioxide in the atmosphere to mosquitoes in the field where the population was exclusively composed of Aedes albopictus (Skuse, 1859). Types of mosquito traps were deviced with which numbers of the mosquito attracted could be counted under various conditions. Physical and chemical factors, such as carbon dioxide, radiating heat, humidity, which would be generated by a host and might act as the attractant of the mosquitoes, were tested by using the traps. The first type of traps was desinged to count the numbers of mosquitoes flying around or staying on a metal can; as for the source of carbon dioxide, a piece of dry-ice covered with a few layers of gauze set on the can was found to be most satisfactory; the effect of heat was observed by placing a glass bottle containing hot water in the can; effects of the surface materials and of the humidity on the number of mosquitoes rested on the traps were tested by covering the can with two layers of gauze soaked in water. Comparative studies were made using several traps with or without setting the factors mentioned above. The second type of traps was constructed to collect the mosquitoes attracted around the equipments placing dry-ice, warm bottles either exposed or covered with gauze layers in a large box, the opening of which could be closed when an observer wanted to finish the experiment. The number of mosquitoes trapped in the box was counted by narcotising them with ether. The results showed the following conclusions : 1. CO_2 exhibitted a remarkable attracting effect on the mosquitoes. If it applied alone without combining other factors, the mosquitoes in the field were attracted and flew around in the range of a few inches from the dry-ice, but did not rest on the surface. 2. Temperature in itself did not attract the mosquito, but obviously increased the number when applied in combination with carbon dioxide; in other words, it acted as the auxiliary attractant. 3. The numbers of resting mosquitoes found on a surface of equipments after attracted by the above stated factors were much influenced by their characters; metal can or glass bottle did not allow the mosquites to rest on the surface, but if covered by gauze, many of them were found to land on it and exhibit biting actions using their proboscis. No significant differences were seen between the numbers of mosquitoes attracted on dry and on wetted gause. Through the above presented results, it is assumed that the mosquitoes are first attracted towards the source of carbon dioxide, then arrested by a heat source of adequate strength, and further select of the surface to rest on will be made by its external characters. Attraction of the mosquitoes showing their biting actions was thus demonstrated by using a model simulated as human body, and a part of the mechanisms of their parasitic activities were analysed.

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The author found the larvae of Aedes rossicus in the wooden tank at Tsuta-Onsen, Towada, Aomori Prefecture, could rear in the laboratory, and obtained male and female specimens and their associated larval and pupal skins. The condition of adult specimens were not so satisfactory, that the male and female terminalia and larva, together with Stackelberg's description of adult were described. Thus all Palearctic species belonging subgenus Aedes (6 species) have been known from Japan, the keys to male and female terminalia and larvae were presented in this paper. Although the adults are hard to identify, presence of additional hairs on siphon of the larva, seta on the process of claspette, shape and number of submedian setae of 9th tergite are distinguished from known species of Japan.

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Experiments were made to estimate the population size and behaviors of commensal rats, Rattus norvegicus and Rattus rattus, by the amount of food consumptions experimentally distributed at various localities in certain buildings. In the first experiment made in an animal house with concrete floor, the amount of food consumed per rat was estimated. In an animal house with concrete floor, baits were distributed at about 20 different localities and the amounts of food consumption were weighed every morning for successive days. After that, collection of rats using snap-traps was made until no more rats could be trapped and no more rat signs were observed. The amount of consumptions at each bait-box varied greatly by the localities, and the home ranges of the rats could thus be estimated. The total amounts of food consumption per day were, however, fairly constant and was calculated as 8.1g per day per rat in ricebran, 9.8g in dog biscuit, 8.7g in cerials and 9.4g in the same cerial containing warfarin. Experiments repeated under similar conditions yielded values of related level. In the next stage of experiments made under the environments where it was difficult to trap all of the rats inhabiting the areas, the value of food consumptions per rat was estimated by comparing the differences of the consumed amounts before and after trappings with the number of rats killed by the traps. The results were 14 to 15g in one colony, and 30g in the other. In a laboratory observations made with nine brown rats with the average body weight of 134g, which were kept isolately in cages, the average amount of consumption of dog-food per day was 20g and that of water 27cc. Home ranges as well as the movements of colonies of the brown rats were observed in an laboratory-animal shed by applying the bait method and the trapping methods, under mark-and-release system or snap-trap system. In the first period of observations, the activities of a colony were confined to the east side of the house. After about 45 days, an invasion of a new colony took place in the other side of the building. Comparative studies were made with a number of diets composed of different mixtures of food materials. Maximum values of consumption was seen in the mixture of wheat flour, corn meal and cooking oil. The amounts of food consumption by rats are influenced by their body weights, the kinds of baits and also by the environments. Estimation of the population size as well as its movements may be estimated to certain extent by the above stated bait-method if such factors would be taken into considerations.

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1) The specimens of the black fly were collected in the city areas of Tottori and Yonago. 2) Eggs, larvae and pupae of the species were identified, and the morphology for all stages of its development was clarified and described. 3) This species was clarified to belong to the subgenus Boophthora Enderlein. 4) This species appears to be new, and Simulium (Boophthora) yonagoense was proposed as the new name. 5) Laboratory rearing of this species from egg to adult could be successfully carried out using the method similar as the rearing method of S. salopiense reported by Yoshida and Nakanishi in 1956. 6) The larval stage reared at 10 to 15℃ was for 26 to 31 days, and at about 20℃ for 13 to 24 days. 7) The pupal stage at about 10℃ was for 9 to 12 days, averaging about 10 days, and at about 20℃ for 2 to 6 days, averaging a little more than 3 days. 8) The size of the adults reared indoors from eggs was not much different from that collected in the nature. The sex ratio of the species generated indoors was also practically the same as that observed in the nature. 9) The present species is distinguished from S. argyreatum, S. heringi, and S. bujakovi of the same subgenus by the absence of spots and the presence of sparse silver-white pubescence on the mesonotum and by blackish brown color all over the femora. The present species is also distinguished from its morphologically similar species of S. tuberosum by the velvet black mesonotum, by the color of the pubescence of the mesonotum, and by the dendriform construction of the respiratory filament.

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The reactions of full grown larvae of S. salopiense and S. aokii to lindane and DDT were studied in the laboratory. The LD_<50> after 30 seconds exposure are 4ppm in lindane emulsion, 54ppm in DDT emulsion and 105ppm in DDT paste, respectively. The LT_<50> in 1ppm lindane emulsion, 10ppm DDT emulsion and 10ppm DDT paste are 1 minute, 1.7 minutes and 5 minutes, respectively. On this observations, moreover, considerable numbers of larvae have pupated after 30 seconds exposure in high concentration of insecticides. These results suggest that the Simulium larvae have no small resistance against these insecticides.

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In this paper it is given the result of one year's observation beginning April, 1956 on the prevalence of various Diptera collected from a poultry ranch in Kaida, Hirosima Prefecture, Japan. The poultry ranch and the breeding boxes surveyed are shown in Fig. 1 and 2. The flies were bred to the adults from a certain amount (each about 3kg) of chicken excrements. Fifteen species of flies were collected, these are devisible into 11 genera, which are classified into 8 families (Table 1). The dominant species were Tephrochlamys sp., Fannia sp. I, Fannia sp. II and Ptecticus tenebrifer. But, these are, as is shown by their behavior, the fly species of lesser public health importance. However, it is worthy to note from the view point of the fly control program, that there found flies of public health importance such as Musca vicina, Stomoxys calcitrans, Muscina stabulans, Fannia canicularis, Calliphora lata, Sarcophaga peregrina and etc., in a considerable number. The majority of them emerged out during May to September.

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One percent emulsion of malathion, dipterex and dieldrin were sprayed on manure heaps at the rate of 0.5 litre per square foot, and the effects against the house fly larvae were estimated by the ratio of the emergence. In all cases, the killing effects were from 80 to 100 percent. While 0.01% emulsion of malathion, dipterex and dieldrin were sprayed, the effects were only a few percent. One percent malathion emulsion was sprayed against the side walls of pens at the rate of 80cc per square meter and the effect on the house fly population was estimated by counting the number of adults found on hog bodies. The house fly population remarkably dropped for at least in a period of one week after the application. The residual effects, however, could be demonstrated for three weeks.

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The author has collected the oribatid mites in various parts of Japan. Three methods of collection were applied; Modified Berlese's funnel method (drying cone method), Watanabe's wood plate method and Direct collection technic. Berlese's funnel method was one of the best technics for the survey of the fauna of the mites. Direct collection method with badger hair brush was most simple but non-efficient technic. Watanabe's collection technic with wood plate was one of the effective and simple methods of collection for oribatid mites, especially Oribatula sp. (Or. -1). The author also collected this species by the same method. Tested woods were fresh cider and old pine plate. Many mites were collected on pine plate in the morning. Collected mites were kept in plastic vessel, which contained plaster of Paris and charcoal in the bottom. In this medium the adult mites lived for several months to one year. In the early autumn of 1957, the diurnal rhythmic activity of oribatid mites, Oribatula sp. (Or. -1), the intermediate host of Moniezia expansa in Japan was observed in a pine-forest in Kashiwazaki City, Niigata Prefecture, Japan. The number of the oribatid mites observed on the undersurface of old pine plates, which had been placed on the ground 12 hours before the observations were counted every hour for 26 hours. The number of observed mites on the undersurface of plates was about 70% of the total number counted on both sides of the plates. The ratio was almost constant in the daytime (from 7.00 A.M. to 10.00 A.M.) as well as in the night time (from 6.00 P.M. to 5.00 A.M.). The number of mites observed on cider plates were less in number than on pine plates. The environmental factors as the soil temperature 5cm beneath the ground surface, the air temperature and relative humidity 5cm above the soil surface, were recorded at the each time of observations. It was revealed that the number of the mites observed on the undersurface of pine plates showed significant positive correlation to the air and soil temperature.

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The investigations of the distributions of early stages of black flies in Nasu area, Kanto district, were made by the authors, in October, 1956 and January, 1957. The species collected in the area of about 500km^3, are shown in the list. The majority of the specimens collected were occupied by S. venustum, S. ornatum and S. bidentatum. The phenomenon of the habitat segregation in a stream (River Sabi) was observed. And according to the distribution of black flies, this stream seemed to devide into 3 habitat groups, consisting P. hirtipes+S. japonicum; S. venustum+S. bidentatum+S. ornatum+S. aokii+S. decorum+S. tuberosum+S. subcostatum+S. uchidai; S. bidentatum+S. venustum, respectively.

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