The cross-section of the malpighian tubules often shows 2 or 3 relatively large epithelial cells, resting on a thin basement membrane. Basal, intermediate and apical zones of each cell exhibit a characteristic structural appearance. The basal zone, where many mitochondria and vacuoles are located, is characterized by infoldings of the cell membrane, namely, a basal striation. The intermediate zone contains a number of vacuoles of varying sizes, and lime granules are 0.1 to 3 microns in diameter. Each of these granules is constructed of 2 to 7 layers. In addition, many mitochondria and coarse endoplasmic reticulum are seen near the apical zone. Clods of electron-dense granules, about 400Å in diameter, are scattered in the basal and intermediate zones. In the apical zone which forms the brush border, a multitude of vertically arranged protoplasmic processes are seen. Each process contains a mitochondrion whose cristae run mostly parallel to the process.

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The observations were made on the bionomics of larvae and on the blood-sucking behaviour of adults of the deerfly, Chrysops suavis Loew, in Kozu pasture in Gunma Prefecture. Most of the larvae of Chrysops suavis were found in 5cm depth from the sandy soil surface in an artifitial pond and usually 40cm apart from the edge of the waterbody. No larva found in swamps or streams in the pasture. Its pupal period on an average, was 10.13±2.76 days. It took roughly 1 to 2 minutes for the molting of pupae. The emargence took place during 9 to 11 a.m. and 3 to 5 p.m. in many cases. The diurnal rhythm of blood-sucking activity of Chrysops suavis apparently had two distinct peaks, one in the morning and the other in late afternoon, as shown by the number of flies on cattle hosts. The adults of Chrysops suavis attack mainly on the scrota of the ox and the horse. The adults attack neither on the back nor the side of the animals.

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Observations were made on the horse fly, Tabanus iyoensis Shiraki, at Nakanokouchi, Toyama Prefecture, in early fall of 1968, using the collection methods with dry ice light traps and insect nets. The results were as follows : 1. Carbon dioxide gas was found to have a remarkable attracting effect on the female horsefly and large numbers of them could be collected in the dry ice traps shown in Fig. 3. Remarkable increases were seen in the number collected in the trap with dry ice during the daytime from 10 a.m. to 7 p.m. in comparison with the control trap without dry ice. 2. No consistent differences were seen between the numbers collected in the traps covered with black or white sheets. 3. The horse fly was observed to be attracted to electric light (fluorescent lamp, green and blue light) in the evening. 4. Their flight activity was found to be enhanced by the movement of a vehicle, and by waving of insect nets. Large numbers of the horse-fly could be collected with the insect net particularly in early morning and at dusk. 5. Preliminary studies on the population density and the flight range of this species of horse-flies were conducted by the mark and release method, in which about 1 and 5 percent of the population were recaptured with the dry ice traps and the insect nets at the two trials. 6. The flight and the biting activity of the horse-fly were observed in the temperature range of 20°to 26℃ and during the daytime under illumination of 10 to 1, 000 lux, but not at temperatures below 15℃ nor in complete darkness. In this connection, their activity was found to be the highest in the morning and at dusk in midsummer, and at the daytime in the autumn season.

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Field observations were made during the summer seasons of 1967 and 1968 in a swamp area of Okayama Prefecture on the biting activity of the mosquito Culex tritaeniorhynchus summorosus, the principal vector of Japanese encephalitis. The nocturnal rhythm of its biting activity was estimated by various methods, such as the counts at half an hour's intervals on pigs, on human baits, and those on plates or tapes set near dry ice baits. Large numbers of the mosquito were found to be attracted to pigs in this area, and the total number of the mosquitoes that engorged from a pig per night was estimated to exceed 50, 000 in the middle of July at its peak of seasonal activity. The nocturnal biting rhythm of the mosquito as seen from the counts on a pig or human body was almost constant throughout the night, usually with two inconspicuous peaks, one at about 9 p.m. and the other at about 2 : 30 a.m. Such a pattern seen with C. t. summorosus was similar to that observed with Anopheles sinensis under the same condition, but was quite different from that of Culex pipiens pallens (one peak at about midnight) or of Armigeres subalbatus (two peaks, at about sunset and sunrise time). C. t. summorosus was found to attack all body parts of the pig almost evenly, while A. sinensis was seen to attack predominantly on the bellylegs and head, and only rarely on the back and sides of the pig. The same group of mosquitoes were attracted to dry ice placed on the ground surface, and their nocturnal rhythm could be observed also by counting the numbers resting temporally on plates set near the carbondioxide source, or those trapped on adhesive fly paper. In these observations activity of the female C. t. summorosus was seen to have two peaks also during the hours from 8 to 9 p.m. and from 2 to 3 a.m., which were more sharply defined than observed from the direct counts on animal baits. The numbers of mosquitos recorded on the plates or tapes decreased in relation to the distance from the carbon dioxide source, roughly with an inverse proportion.

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1. A seasonal study was carried out on the mosquito population breeding in rock pools in the river bed of Nagatoro, Saitama Prefecture, during the period from January 1966 to February 1968, with emphasis on the bionomics of the little known mosquito species Aedes hatorii Yamada, 1921. 2. As the results of 50 times of collections made during the period, a total of 53, 148 larvae belonging to 10 species in 3 genera were identified. Among them, Aedes hatorii was the predominant and constituted 84.7% of the larvae and pupae collected, while Aedes japonicus was the next common species with 9.7% of the total collections. 3. The population density of Aedes hatorii was the highest during the summer season from July to September, while Aedes japonicus was almost absent in the summer and was found to be breeding most abundantly in early spring. 4. The two species were shown to survive the winter in egg and or mature larval stages. 5. The principal breeding places of Aedes japonicus were rock pools in shade, while Aedes hatorii was found almost in every pool including those in open areas.

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A series of experiments were carried out on the effects of some insecticides on the tropical rat mite, Ornithonyssus bacoti, in the laboratory for the screening tests of antifilarial drugs using the cotton rat filaria, Litomosoides carinii. For this purpose, it is necessary to breed large numbers of the mite in the laboratory to serve them as the intermediate host, but on the other hand, it is also important to get rid of the mite from the animal room to avoid spontaneous infection of the animals. As preliminary experiments to find out the effects of insecticides under simulated conditions, cotton, wirescreen and the cotton rat's body surface were treated with 0.3, 0.1, 0.03, 0.01 and 0.003 percent emulsion in water of the five insecticides, malathion, fenitrothion (Sumithion), diazinone, dichlorvos (DDVP) and lindane. Certain numbers of the mite were released on these materials treated under various conditions, and the mortality after one to 24 hours were recorded. Among the insecticides thus tested, fenitrothion and diazinone were the most effective, and nearly 100 percent mortality was seen even at the lowest concentration of 0.003 percent, while the other two organophosphorous insecticides, malathion and dichlorvos were effective up to 0.01 or 0.03 percent. No satisfactory effect were seen for lindane even at the highest concentration of 0.3 percent. At applications on the cotton rat's body, some toxic effects were seen in diazinone, dichlorvos and lindane. The residual effects of the insecticides were also tested at various time intervals from applications of 0.03 percent emulsions on various materials. In general, the longest effects were observed for all the insecticides when cotton was used as the substratum, and nearly 100 percent mortality was seen even after 32 days in fenitrothion, malathion and diazinone, while the effects were shorter when the insecticides were applied on wirescreen. The effects of the insecticides applied on the cotton rat's body surface were much shorter, and were found to be lost almost completely after 8 days of the application for all the insecticides. Among the insecticides tested, fenitrothion showed the longest residual effects in all the cases, and malathion was the next in the order. In the practical use of insecticides for the control of the tropical rat mite in animal houses, spray of 0.01 percent emulsion of fenitrothion or malathion on animal cages gave satisfactory results, and no toxic effects were seen in the animals. In general, fenitrothion is considered to be the choice because of its higher effectiveness, longer residual effects and lower toxicity. However, in our special animal rooms in which the rats are used repeatedly as the hosts for the mites, malathion has been used to remove the mites from animal cages for the sake of safety for the following biting experiments, since the compound has shorter residual effects than fenitrothion.

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A series of laboratory tests were carried out to estimate the contact toxicity of some insecticides and acaricides against the tick, Argas japonicus collected from nests of the swallow, Delicnon urbica. The compounds tested were DDT, lindane, dieldrin, DDVP, malathion, fenthion (Baytex), fenitrothion (Sumithion), EPN, Kelthane, Phenkapton and Akar. Emulsions of the compounds were diluted with deionized water to concentration 1.0, 0.1, 0.01 and 0.001 percent, and were impregnated in filter papers at a rate of 50ml/m^2. Mortality of the ticks was recorded after being exposed to the residual deposits for 48 hours. The comparative toxicity of the compounds tested by this method was by the order of lindane, dieldrin, DDVP, Sumithion=malathion and EPN, and the other compounds were shown to be almost ineffective, as shown in Table 1. Hundred percent mortality was observed with lindane at 0.1 percent and with dieldrin and DDVP at 1.0 percent. At the observations on the knock down percentage of the ticks in relation to the time of exposure to deposits of 1.0 percent emulsions. KT-50 value was by the order of lindane (93 minutes), DDVP (165 minutes) and dieldrin (460 minutes).

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Ces dernieres annees, la generalisation des bombes aerosole insecticides est bien remarquable au point que tous les insecticides pour l'usage domestique adopte le type decrit ci-dessus. Il est donc necessaire de constater une methode simple, rapide et assez precise pour permettre une mesure relative de l'efficacite insecticide des bombes aerosols commerciaux. En generale, la methode de Peet-Grady est, jusqu'a present, utilisee en Europe et en Amerique mais elle ne serait pas toujours la meilleure. Dans ce note, les auteurs rapportent les resultats obtenues apres avoir verifier quelques methodes pour constater une methode valable ci-dessus. Les auteurs ont utilise les trois methodes : celle de Peet-Grady appliquee aux pays europeens et en Amerique; celle de l'appareil du type Boite a 0.5m^3 decrite dans le guide d'Insecticide (1965); enfin celle du type DS prepare par la Station de Phytopharmacie de l'Etat, Gembloux (Belgique). Les bombes utilisees sont les aerosols contenant du Neopynamin a 0.2% en solution dans l'eau et l'huile. L'insecte-teste est effectue chez la mouche domestique (Musca domestica vicina Masque, la souche Takatsuki) eleve de generation en generation au laboratoire et adulte agee de 5 jours apres l'emergence. Les resultats obtenues sont la suivante. 1°Parmis trois methode, il est en evidence que la methode du type DS a la plus grande efficacite pour le teste insecticide. L'appareil au type Boite a 0.5m^3 suit celui du type DS. 2°Au point de vue economique, l'appareil au type Boite a 0.5m^3 est moins couteux que celui a DS. 3°Quant a l'effet de solvant, on a observe la difference entre l'aerosol a l'huile et celui aqueux; l'efficacite de la methode ne subit pas sur sa efficacite. 4°Les auteurs concluent qu'il estev desirable d'utiliser simultanement la methode du type DS et celle du type Boite a 0.5m^3 pour proceder a l'etude de l'amelioration des insecticides.

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