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In the preceding experiments, methionine was found to enhance the attractiveness of mice for mosquito biting when an aqueous solution was inpregnated on the body surface. Further experimentation on this was conducted by injection of 0.1ml. of 0.5% methionine into a mouse intraperitoneally. Since there was no significant increase of methionine in the blood serum of the treated mice, and since blocking the metabolic pathways of methionine by addition of ethionine cancelled the enhanced attractiveness, some metabolites rather than the intact methionine were suspected to be responsible for this effect. Following the metabolic pathways of methionine in vivo, various probable metabolites were tested, and glycine was found to enhance attractiveness significantly, and cysteine and pyruvic acid somewhat less. Other probable metabolic compounds, creatine, choline and cystine, and taurine and urea actually detected by chromatographic analysis of the blood serum did not contribute to increased attractiveness. Since the contents of glycine and cysteine did not increase significantly in the blood serum when treated mice exhibited the enhanced effect, further metabolic compounds of these are suspected to be responsible for this. The desulfulization process of cysteine to pyruvic acid could not be related to this effect.

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A series of studies on mosquitoes and their role as vectors of human diseases have been carried out by the members of our Department during the past ten years, and some of the results have been reported in connection with the epidemiology of filariasis in the Amami Islands. In this paper an account is given of a mosquito, Anopheles bengalensis, which was found in limpid waters of small streams, irrigation ditches, springs, stream beds, rock-pools etc. of lowland forests on Amami-oshima and Tokunoshima. These specimens are the northernmost collection yet of mosquitoes of the A. aitkenii group, which has not been collected from the other districts of Japan or from the Ryukyu Islands. Small, brownish and unspotted adult resembles A. aitkenii, A. fragilis and A. acaci. The dorsal lobe of the male claspette bears 2 club-like and 2 sword-like spines. The inner clypeal hairs of the larvae are 2 to 7 branched. Some morphological variations of the branches of inner clypeal hairs, abdominal lateral hairs III and the saddle hairs are shown in table 1.

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The seasonal occurrence of the "Habu" viper, Trimeresurus flavoviridis, was observed from 1959 to 1962 through the captivity of the snakes. The number of the snakes captured and offered to the Health Center showed one prominent peak in June every years. The seasonal occurrence of the snake bite showed two peaks; one in June and another in early autumn. The loose correlation existed between the seasonal occurrence of the snakes and the snake bite (0.01<P<0.05). The activity of the snakes observed in a snake pit was absolutely nocturnal. In the time difference of the snake bite demonstrated by Sasa, Tanaka et al. (1956), the bite occurred mainly in the daytime making two peaks at 10 a.m. and 8 p.m. The close negative correlation was found between the hourly change of the snakes' activity and the snake bite (P<0.005). The hourly change of the bite occurrence was assumed not to be influenced by the change of the activity of the snakes but to be attributable to the human activity in the field.

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Screening tests for various aerosol formulations of active insecticides necessitate a device which can deliver an accurate volume of aerosol insectisides at an extremely short period. For this need, an automatic mechanical device was invented. The present device is composed of a time gear which can be pre-set at any time between 0.1 sec. to 30 sec., and a magnet of which arm presses a nozzle button of an aerosol can with the constant pressure of 2kg/cm^2. A spring coil on the nozzle button, instead, pushes back the magnet-arm to cases spraying when an electric current is cut off automatically. By spraying the aerosol containing 0.3% DDVP, 0.1% pyrethrin and 1 mC of P^<32> in 90ml of xylene through 50cm long, and 9cm wide glass cylinder kept horizontally under a hood, 10 house flies were exposed at the other end of the cylinder for a test. Eight time repetitions were made for each spraying test pressed by either the device or a finger. At 10 seconds after puffing the aerosol, the air under the hood was ventilated and the number of house flies was counted. The doses of insecticide attached to house flies were calculated from the radioactivities picked up. The device was satisfactory on the following points and proved to be useful for testing aerosol formulations of active insecticides : 1) KT-50s increased proportionately with increase of the reciprocal values of time when sprayed by the device, however, irregularly by the finger. Especially, in such an extremely short spray as 0.2 sec. the finger could not control the time and tended to press longer. The standard deviations of the knock-down time were smaller when pressed by the device than by finger. This fact is of prime importance since the smaller deviations make the comparison among different candidate formulations more accurate. 2) The radioactivities, namely, the doses of insecticides picked by house flies also showed the proportional increase in accordance with increase of spraying periods when pressed by the device, but not so by finger. The standard deviations of the radioactivities of house flies were, however, indifferent between the tests by the device and by finger. There was a fine linear relationship between the log.-KT-50 and the log.-mean volume of insecticide attached to the house flies.

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Laboratory tests were conducted on sterilizing effects of the chemosterilants, metepa and hempa on a laboratory colony of the mosquito Culex pipiens, form molestus. The chemicals, mixed with sugar solution, were applied to the adults by a bait method and dissolved in water at given concentration to the larvae by a dipping method. Results recorded were; the numbers of egg rafts produced per female; the average number of eggs per raft; and the sterility rate of the eggs in total. After exposure of mixed populations of males and females to baits of sugar solutions containing 0.1 and 0.01 percent of metepa, the sterility rates were 83.7 and 78.2 percent, respectively, while little effect was seen with 0.001 percent solution of the same compound. A solution of 0.1 percent hempa applied by the same method was effective also, and caused of a sterility rate of 91.3 percent. However this compound at concentrations of 0.01 percent and less did not give satisfactory results. Another series of experiments were conducted for the purpose of observing the effectiveness of the compounds according to sex. Males and females were exposed to given concentrations of the chemosterilants in separate cases, and were released in other cages together with males and females, both either treated or untreated. In the population composed of males and females both treated with 0.01 percent of metepa, the sterility rate was almost 100 percent. In the populations with only the males or only the females treated, the rates were 92.4 percent and 92.6 percent, respectively. Metepa showed almost equal effects on both sexes, while hmeap was apparently more effective against the females than against the males. The 50 percent sterilizing concentration (SC-50) of metepa in treatments of both sexes was estimated to be between 0.001 and 0.01 percent under the above conditions, while that for hempa turned out to be around 0.01 percent. No noticeable reduction in mating activity was seen in males thus treated with chemosterilants. In the populations exposed to 0.01 percent solution of metepa and 0.1 percent of hempa for 24 hours in larval stages, remarkable reductions were seen in the number of egg rafts deposited, and the sterility rate of the eggs reached to 50.8 and 98.4 percent, respectively. However, few effects were seen with the solutions of lower concentrations for both compounds, while those of higher concentrations such as 0.1 percent hempa were also ineffective as chemosterilants because the mortalities in the larval stages were extremely high due to the toxicity of the compounds. It is therefore considered that practical application as larval chemosterilants might be difficult since the range of effective concentrations of these two compounds seems to be quite narrow.

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Sterilizing effectiveness of gamma radiation with Co^<60> or chemosterilants on the engorged female cattle tick, Boophilus microplus, was determined. Doses of 10 to 100 kr were inhibitory to oviposition. A 50% hatchability was shown by eggs deposited by females irradiated at a dose of about 0.5kr. Thiotepa was the most potent sterilant of the chemicals tested, and followed by apholate and metepa in this regard. Hempa was lower in the degree of effectiveness than any other chemicals tested. In these chemosterilants, a 50% sterilizing dose were in a range from 1.5 to 2500γ per gram of body weight by topical application. These results were similar to those obtained from many other insecti- and acaricides having an oviposition-inhibiting action upon the tick.

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An experiment on the insecticidal effect of the emulsion of BHC, Sevin, and of their mixture (1; 1, v/v) on the common housefly, Musca domestica vicina, was carried out in 1964 at Miki-cho, Kagawa Prefecture. The results were summarized as follows : 1) The effect of BHC-emulsion on the adult fly was much greater than that of Sevin-emulsion, and the mode of action of both insecticides to the fly seemed to be different from each other. 2) The equivalent mixture of BHC-emulsion and Sevin-emulsion did not show any particular action such as synergistic action, but showed only the independent joint action.

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The studies on the effect of some organophosphorus compounds against dieldrin-resistant and -susceptible colonies of Blattella germanica were carried out. The residue of diazinon, fenitrothion or fenthion was highly effective to the dieldrinresistant colony, as well as to the dieldrin-susceptible colony. The contact only for 10 to 60 minutes to the residue of 2.5g/m^2 of each compound was enough to kill all of the female cockroaches within 6 days after the contact. Meanwhile, dieldrin and chlordane were far less effective to dieldrin-resistant roaches. The continuous contact for 2 days to the residue of 2.5g/m^2 of both chemicals could kill only 23% of the resistant roaches, though the contact for 2 to 10 minutes was enough to kill all of the susceptible roaches. In the fumigating tests of lindane and of the mixture of lindane and dichlorophos, both of them were less effective to dieldrin-resistant colony than to dieldrin-susceptible colony.

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Susceptibility or resistance seen in each colony of Boettcherisca peregrina and Phaenicia cuprina collected in Fukuoka City, Japan in 1966, to DDVP, Dibrom, diazinon, ronnel, Sumithion, Baytex, Dipterex, malathion, tech.-DDT, lindane and dieldrin was assessed by topical application test. The LD-50's represented in microgramme per fly to Boettcherisca peregrina were as follows : DDVP, 0.035; Dibrom, 0.043; diazinon, 0.081; ronnel, 0.105; Sumithion, 0.119; Baytex, 0.182; Dipterex, 0.348; malathion, 0.938; tech.-DDT, 0.492; lindane, 1.027; dieldrin, 98.146. Those to Phaenicia cuprina were as follows : DDVP, 0.007; Dibrom, 0.013; diazinon, 0.020; ronnel, 0.023; Sumithion, 0.033; Baytex, 0.040; Dipterex, 0.065; malathion, 0.264; tech.-DDT, 0.429; lindane, 0.745; dieldrin, 2.896. Each colony of these species was concluded to be susceptible to organophosphorus insecticides, but to be highly resistant to lindane and dieldrin.

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