Seasonal prevelence of mosquitoes were studied during the period from 1952 to 1953, in Yonago City. 1. Four genera, 14 species of adult mosquitoes were collected in the houses and Culex pipiens, C. tritaeniorhynchus and Anopheles sinensis occupied the great majority of the specimens (80-90%). 2. In 1952, the peak of seasonal population curves of C. pipiens lied on the latter part of July, while in 1953, it lied on the middle or latter part of June. 3. Of C. tritaeniorhynchus and A. sinensis, it lied during the period from the latter part of July to the middle of August.

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The work here reported concerns biting-midges collected during the period from May to October, 1956, in Niigata Prefecture, Japan. Culicoides collected are 14 species (See the list of species). C. arakawae has been widely found over the plains and the hilly regions. C. circumscriptus has been prevalent along the seashore and the area of the saline hot-springs. While, C. matsuzawai was prevalent amongst Okutadami, the mountainous district. According to our observations on C. circumscriptus at Matsunoyama-village, the larvae have been abundantly found in the slime of the gutter draining, the water which contains 3% Sod. Chl., 37°, pH 8.5-10.0 and was constantly discharging from the saline hot-spring. And the adults attack violently against human beings and their main biting activity reaches a distinct peak at dusk.

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The effects of larval population density on the body weight, the length of pupae and on the duration of pupation using larvae of the common housefly, Musca domestica vicina MACQ. are presented in this paper. As the culture medium of larvae, mixture of 25g of powdered Oriental Compressed Diet for Experimental Animals (for a mouse, rat and hamster), 25g of wheat bran and 50cc of water kept in a petri dish measuring 9cm in diametar and 6cm in height were prepared. The population of larvae were chosen in twofold steps as 20, 40, 80 160, 320, 640, 1280 and 2560 individuals respectively and some middle scales as 960 and 1920 were added supplementally. Second day's batches of larvae were transferred to dishes and all pupae were served for measurement after 7 days which were cultured at 25℃. Frequency curves of body weight were biassed towards lighter side of the mode in lower population densities. As population densities increase, their forms approached to the normal distribution. The curves moved towards the lighter side in a remarkable degree when densities were 640 or more individuals (Fig. 1). The maximum value of body weight was obtained at the density of 40 individuals, and the body weight decreased gradually as the increase of population density up to 320, but it decreased remarkable when the density rose to 640. It seemed that the lowest level was kept within certain limits of fluctuation in higher population densities. Mean lengths of pupae were longer and their standard deviations were smaller in a range of wider population densities compared with Nagasawa's result using "okara" (residual product of bean-curd) medium (Fig. 2). The pupation was accomplished from 5 to 9 days after the oviposition in the population densities between 20 and 320 individuals, but the duration prolonged from 5 to 16 days when the population density attained over 640. The mass weight as well as the number of pupae recovered at various population densities were plotted on the double logarithmic scales. The value fitted well in linear regression in the range of from 20 to 320 larvae in the former and from 20 to 640 in the latter, but were dislocated from them in higher population densities, suggesting there existed another phase of population effects (Fig. 4). Furthermore, a significant negative correlation was seen between the number of pupae recovered and their body weight in the dislocated part. From the ecological concept, the productivity of culture medium will be expressed as density-proportional to the biomass until the population density reaching 320 individuals, as density-independent when over that densiy it sustains constant biomasses for a results of intraspecific competition which would been occurred by the population pressure. The population density of 320 individuals was assumed the optimum for mass culture of the common housefly under this culture condition from the following facts. Under this population density, no distinct decrease in the body weight was demonstrated comparing with those of lower populations. The rate of pupation in the density of 20 to 640 increase in some degree, but 320 group showed the best reproducible results. Until 320 individuals, duration of pupation little varies in the increase of the population density.

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The surveys on larval habitats of flies of medical importance were carried out on July 1957, at the residential quarter of Mitsubishi Kogyo Co. in Ashibetsu City, Hokkaido and the most important habitat of the larva, Fannia canicularis, the dominant species in houses of this district, was found in steeper of 'Takuwan', Japanese pickled garden radishes using rice-bran and salt as media. F. can. was found in steepers of 56 families and Muscina stabulans was found in 28 families out of 112. While, by the general surveys following species of fly larvae were collected.. Garbage box : Phaenicia sericata, Ophyra leucostoma, M. stabulans (these three species occupied the majority number of individuals), F. can., Sarcophaga peregrina and Lucilia illustris.; Lavatory : Calliphora lata, S. pereg., S. similis (those three showed majority number), F. can., F. scalaris and M. stab.; Pig-pen : M. stab. and Lucilidae sp.; Chicken house : F. can. and O. leuc.; Rabbit house : O. leuc.; Vegetable manure heap : Sarcophagidae sp.. Number of individuals collected from animal sheds was few. From the results obtained by the surveys in Ashibetsu, similar surveys on steepers were carried out at several districts in Hokkaido, Akita, Tokyo and Kanagawa on July, August for comparison. High popularized rate of 'Takuwan' was observed in rural and fishery villages than town district and high occurrence rate of F. can. was found in northern part of Japan than the south. The larvae found in Takuwan steepers were swarms of F. can. alone or mixture of F. can. and M. stab. and no swarm of M. stab. alone was found. The occurrences of the two species mentioned above differ by the conditions inside of steeper, i. e. M. stab. seems to like more water content in the media than F. can.. Although the most important habitat of F. can. larvae in Hokkaido is 'Takuwan' steeper, but habitats as lavatory and animal shed may have also importance in town district of Honshu and southern part of Japan. The control method for steeper was discussed in this paper, but the problems of other habitats and their control will be studied and discussed in the future.

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In order to estimate the residual effect of several organic insecticides using adult German roach a model method designed by the author was introduced. The residual effect was judged by the knockdown percentage, at intervals up to six months after the application. It has been shown that the efficient duration of the test insecticides as shown by 95% knockdown, was in the following sequence : 0.5% Dieldrin oil solution, six months; 0.5% Diazinon oil solution and mixed with 5% DDT plus 0.2%γ-BHC oil solution, two months; 0.5% γ-BHC oil solution, fifteen days. 5% DDT oil solution gave no 95% knockdown. Even in the initial toxicity DDT was lower than any of the other compounds, but, throughout the duration of experiment, it showed a residue persistence at about 77.5% knockdown in average.

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For the purpose of estimating the population size and home ranges of the house rat Rattus norvegicus, an investigation was made in a laboratory animal shed. The effects of snap-traps as the control measure on the rat were also observed after the above stated experiments. The mark and release operation were carried on for successive 8 days, untill no unmarked rats could be recovered. The number of total marked rats attained was 41. Estimation of the population size by the graphic method using the linear equation (E)Y=(N-x)P resulted in 40, thus showing a coincidence between the theoretical and actial sizes. (Y : the ratio of marked individuals to the total number captured in a single operation. N : the number captured. x : the cumulated number of captured rats. p : probability of capturing a rat) The real population size, however, was estimated to be larger, because of the presence of individuals not exposed to the cage-traps. During course of the snap-trap collections made later, 13 unmarked rats were trapped besides 19 marked individuals. The probabilities of capture for unmarked (P) and the marked (π) were calculated as 0.357 and 0.196, respectively. It was presumed in this case that rats, once captured, showed the behaviour to be less easily trapped than the unmarked. The average distance between the localities of the successive captures in each individual was calculated as 6.53m for a male and 4.96m for a female. Home ranges of 50% of the males were estimated as less than 36.1 square meters, and as 33.5 square meters in the females. The males seemed to cover more areas than the females.

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Surveys on the ectoparasites of the wood mice, Apodemus speciosus, at several plots in Wakayama Prefecture have been carried out by the authors since 1954. And part of their results were already reported and analysis on the relationship between species of chigger mites distributed in this district and environmental factors were made in this paper. The name of plots surveyed and dates are as follows : Kimi (Hashimoto-Shi, Feb., 1955), Wakayama-Castle (Wakayama-Shi, Nov., 1954), Tsugi (Hirokawa-Cho, Arita-Gun, Feb., 1956), Karao (Hirokawa-Cho, from July, 1954 to June, 1955), Minabe (Minabe-Cho, Hidaka-Gun, March, 1954), Nishitonda (Tanabe-Shi, March, 1954), Ryujin-Mura, Hidaka-Gun, Apr., 1955), Oshima (Oshima-Mura, Higashimuro-Gun, March, 1956), Nachi (Nachi-Katsuura-Cho, Higashimuro-Gun Aug., 1954), Kitayama (Kitayama-Mura, Higashimuro-Gun, March, 1956). Almost similar results were obtained through the surveys except Kimi area, i. e. similar species were observed and dominant species in each plots were T. fuji and T. kitasatoi. While at Karao area where the seasonal occurrences of larval chiggers were recorded, the dominant species in warm season is T. kitasatoi and T. fuji in cold season. No remarkable differences were found in vegitation and agronomical factors in each plots, but climatic factors, such as average temperature and rainfall of each month, affected on the seasonal occurrence of the larval chigger mites. The chiggers in most of all plots form up rainfall type and the species in colder plots, such as Ryujin and Kitayama, correspond to that of colder season in Karao, the plots where no difference in temprature and more rain are observed, such as Oshima and Nachi, correspond to that of warmer season in Karao, and the plots where no remarkable differences in temperature and rainfall are observed, such as Tsugi, Minabe and Nishitonda, correspond to that of similar season in Karao respectively. Differences in climatic and geographical factors may affect on distribution of the species in Kimi, where the species differs to the other plots.

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Observations on the differences in several species of rodents as the host of Trombicula scutellaris were made in February, 1957, at Hachijo Island, south of Tokyo, where Shichito-type Tsutsugamushi disease was prevalent. Four species of rodents, Mus musculus (laboratory white mouse), Rattus norvegicus (laboratory white rat), Microtus montebelli and Meriones unguiculatus were used as the experimental hosts for comparison. As was reported in the previous papers, unengorged larvae of Trombicula scutellaris were found to form clusters on the soil surface, especially on tops of rocks or stones, in very season of the year. Infestation of the mites on the hosts were caused by contacting the rodents directly with the clusters. The hosts were kept separately in cages shown in Fig. 1, and the number of mites dropped off from hosts were counted every 6 hours. From Mus, Rattus and Meriones, considerable numbers of unengorged larvae were recovered during the first 6 hours, and engorged larvae could obtain between 12 to 78 hours, with a peak at 30 hours. In the case of Microtus, the time required for engorgement of larvae was found to be considerably longer than in the former species, and the peak appeared about 24 hours later, some being still attached even after 78 hours. The ratio of number of engorged larvae to the unengorged one was also higher in Microtus than in the other species. The results seem to have solved at least a part of the question why Microtus in the fields harbour more mites than other rodent species collected in the same localities.

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I. During the investigations of the chigger prarasites of the Japanese hares (Lepus timidus brachyurus, L. t. lyoni, L. t. angustidens) in several Prefectures of Japan, such as Shizuoka, Saitama, Tokyo, Chiba, Yamanashi, Kanagawa, Gunma, Niigata and Fukushima, there were found ten species of chiggers, Trombicula scutellaris, T. fuji, T. pallida, T. palpalis, T. kitasatoi, T. sp., T. japonica, T. ngayoi?, Euschongastia miyagawai and Neoschongastia shiraii, and one undescribed species of the genus Gahrliepia (Walchia). Of these, E. miyagawai was the commonest, for example, 5, 000 specimens of this species were examined on a single host in Shizuoka Prefecture in January. The summary of collection records of the chiggers in the surveys are shown in table 4. II. The species of Gahrliepia (Walchia) is described and named G. (W.) masoni in appreciation of the favor extended to the author by Dr. Richard P. Mason, the Director of the Walter Reed Army Institute of Research, U.S.A. It is characterized by the following features : Galeal seta usually nude, rarely barbed. Palpal femoral, genual, dorsal and ventral tibial setae feathered ; lataral tibial seta usually nude, rarely barbed. Scutum tongue-like, about 1.6 times as long as broad, and much prolonged posteriorly behind the level of posterolateral setae. Usual scutal setae rather slender, with short branches on the entire surface. Sensillary setae capitate, with many fine barbs on the swelled apex. For scutal measurements see table 1. Dorsal setae similar to the usual scutal setae, and arranged typically as 2-6-8-6-6-4-4-2, and about 36 to 38 in number. Sternal setae 2-2. Coxae untisetose. Nude or sensillary setae on legs arranged as in figure 2. It is of interest to note that a microspur is situated proximad of a spur in tarsus I, and tarsus II is absent in a pretarsala, while femur III bears a femorala-like seta having only one or two fine barbs. Types are preservd in the writers' collections which were taken from Lepus timidus brachyurus, L. t. lyoni, L. t. angustidens in Shizuoka, Kanagawa Niigata and Saitama Prefectures. This species is somewhat related to G. (W.) turmalis Gater, 1932, but differs in having branched setae at least on palpal articles II and III. This work is aided in part through a Grant in Aid for Scientific Research under Cont. No. DA-92-557-EFC-23, 611 between Dr. Takeo Tamiya and Office of the Surgeon General, U.S.A.

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1. A new species of chigger mite, Mackiena smadeli n. sp., is first described in this paper. The material consists of five specimens taken from a Japanese hedge-sparrow, Prunella rubida rubida, at Chichibu district, Saitama Prefecture, Japan, on December 24, 1955. This species is named in honour of Dr. Joseph E. Smadel, Acting Director of the National Institute of Health, Bethesda, Md., U.S.A., for his encouragement and favor extended to the study of Tsutsugamushi disease in Japan. 2. This new species is easily distinguished from the known species of the genus, M. empodiformis Traub et Evans, 1950 and M. todai Kamo, 1953, by a nude galeal seta, a nude ventral seta of palpal article IV, concave posterior margin of scutum, sensillae situated anteriorly far beyond the level of posterolateral setae, and also by the arrangement of dorsal and sternal setae, 4(5)-6-6(4)-4(6)-2(4)-4(2)-2 and 2-2-2 respectively. 3. Observations are extended to the other Japanese species of this genus, M. todai, which prove the presence of "terminalia" on each of tarsi I and II in opposition to Kamo's original description. On the other hand, it is ratified that the tarsus I is lacking in "parasubterminalia" in M. todai as well as in M. smadeli. 4. In connection with the description of M. smadeli, additional measurement units are proposed here for a previous set of "standard measurements or data of scutum". Those units are devised if possible to clarify the relative positions of scutal setae as follows : AMA-Distance between bases of anteromedian and anterlateral setae AMS-Distance between bases of anteromedian seta and one sensillaly base AMP-Distance between bases of anteromedian and posterolateral setae This work is aided in part through a Grant in Aid for Scientific Research under Cont. No. DA-92-557-FEC-23, 611 between Dr. Takeo Tamiya and Office of the Surgeon General, U.S.A.

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For two years from 1954 to 1955 we collected the fauna of fly using the various traps in Osaka City, it was recognized that the catch feature of fly was different in each traps, and therefore it is necessary to the absolute numbers of fly in a certain area is determined to considered the kind of the traps.

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[in Japanese]

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