Chironomid larvae produced the growth-retarding and toxic factors when they were kept under an extreme overcrowded condition in the laboratory. These factors were isolated with the TLC of silica gel and identified as calcium nitrite by means of IR spectroscopy. Accumulation of calcium nitrite in the ovecrowded breeding water was detrimental particularly to the younger instar larvae. Bioassay of the authentic nitrites, nitrates and the related compounds showed that ammonium nitrite and hydroxylamine were also toxic to the same extent. The possible oxygen-deficient condition created by the reduction and decomposition of the accumulated nitrites and nitrates, and the methemoglobinemia caused by calcium nitrite would be responsible to the toxic and growth-retarding actions against Chironomid larvae.

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The toxicity of diphacinone (2-diphenylacetyl-1,3-indandione) to rats and mice was determined for its possible use as an indirect anticoagulant rodenticide. The values of oral acute LD_<50> against the males and females of albino rat were 43.3 and 22.7mg/kg, and those against the males and females of laboratory mice were 30.0 and 28.3mg/kg, respectively. The death usually occurred in 1 to 5 days and the increased dose shortened the survival period. In the case of subacute toxicity of diphacinone against mice, 60 to 100% mortalities were obtained after the successive administrations of diphacinone baits ranging from 0.0005 to 0.02% for six days. No appreciable relationship between the mortality and the total intake dose was found in the range from 0.6 to 200mg/kg. Whereas, the subacute toxicity of diphacinone baits against the albino rats was approximately the same as that of coumatetralyl. Majorities of the mice and rats in these subacute toxicity tests died in 4 to 6 days and 4 to 7 days, respectively. The acceptance of the diphacinone baits was good in mice and rats. The oral acute and subacute toxicities of several indirect anticoagulant rodenticides were discussed in comparison.

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The stage composition of P. japonica populations overwintering outdoors in Niigata Prefecture was investigated. The populations consisted of two groups in terms of their developmental stage, final instar nymphs and much younger ones. More than 50% of the latter were second instar nymphs. The results obtained here would substantially support the speculation of Tsuji and Mizuno (1972).

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Insecticide susceptibility of 4th instar larvae and adults of Culex tritaeniorhynchus summorosus was studied using dipping method and topical application method. The mosquitoes of OK7 strain were reared and maintained from eggs laid by wild-caught adults in Osaka district, 1967. The following results were obtained. 1. LC_<50> of 13 insecticides were determined and may be divided into four groups as follows in descending order : 1) dursban, karphos, abate, Dowco 214 and methyl-parathion 2) fenthion, pp'-DDT and trichlorfon 3) fenitrothion, fenchlorfos, diazinon and malathion 4) γ-BHC. Gamma BHC was most inferior to above chemicals. 2. The larvae of OK7 strain were highly resistant to DDT and BHC. The LC_<50> of pp'-DDT in OK7 strain was ten times more than that of Okayama colony, and that of γ-BHC 250 times more than that of Jindaiji colony. From the data of insecticide susceptibility of C. tritaeniorhynchus summorosus larvae reported by several workers from various localities in Japan, this mosquito seems to have developed more and more resistance to DDT and BHC with years. 3. Refering to the degree of susceptibility to the organophosphorous compounds, the OK7 strain seems to stand at the medium position among the strains reported. 4. The effect of temperature on the toxicity of insecticides was tested with larvae. The toxicity of pp'-DDT and γ-BHC was showed to increase with lower temperature and that of fenitrothion and fenthion to behave reversely.

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Injuries by stings of unknown agents have been reported to occur among the swimmers in the rocky seaweed-growing seashore areas of Niigata Prefecture. The stings were seen among the bathers and the seaweed-collecting divers in summer season and caused the local initial skin lesions in most cases. Usually a variety of general symptoms followed. In order to investigate the causative agent of this sting, the clinical, epidemiological studies and the toxicological experiments have been carried out since July, 1970. The results obtained so far are as follows : 1) The stings took place during the period from the middle of June to the end of August with the greatest number of cases occurring in the second and last decades of July. Most victims were under twenty years of age but the cases of the woman seaweed collectors were older. The severe cases were observed especially in these woman divers. 2) The stings occurred mainly on the skin of the trunk covered by the swimming suit. At the site of sting, usually the initial pain was present and the localized erythematous patch up to several cm in diameter followed. 3) The general symptoms consisted of severe pains in the various groups of muscles, oppression of chest, coughing, lacrimation, serous rhinorrhea, nausea, vomiting, fever etc., and in general the recovery occurred in 1 or 2 days. In severe cases the victims were sent to hospital because of severe pains and dysbasia, and had to receive approximately one week's medical attention. The same symptoms were occasionally seen by eating a kind of seaweed Nemacystus decipiens (Suringar) in raw condition. 4) The etiological investigations have been made to find out a small poisonous jellyfish in the rocky seaweed-growing locality where the victims were stung, since such clinical and epidemiological aspects seemed to refer to the sting by it. Consequently, a small jellyfish measuring 5&acd;15mm in diameter Gonionemus oshoro Uchida has been discovered in accordance with the seasonal occurrence of victims. 5) Some victims have told us to see a small jellyfish-like agent at the sting site under the swimming suit. It is also possible that such a jellyfish got between the swimming suit and the skin of trunk may result in simultaneously discharging the venom of numerous nematocysts into the skin of victims. 6) The assaying of the venom of nematocyst extracted from G. oshoro showed that some signs similar to human cases were produced when the extract was intraperitoneally inoculated into mice and guinea pigs. 7) Two Japanese monkeys showed some symptoms similar to human cases when three G. oshoro were applied to the skin of both superior palpebral regions and one side of buccal region, respectively. 8) Finally a G. oshoro was applied to the skin of the anterior cubital or medial brachial region of five volunteers, respectively, and three persons exposed produced the local and general symptoms corresponding to those mentioned above, while two remaining persons showed only a slight local symptom. 9) Other epidemiological date also have suggested that G. oshoro must be responsible for this injurious effect. The severity of the victims may be modified by sensitivity of the individual to venom, and a hypersensitivity phenomenon encountered occasionally in the woman divers could be an anaphylactic reaction produced by the recurrent stings. On the other hand, the similar symptoms observed in people who ate N. decipiens in raw condition are probably due to swallowing of G. oshoro with such a seaweed. 10) G. oshoro appears to harbor mainly in a seaweed Sargassum confusum Agardh, and it is indicated that these stings may occur widely along the rocky seaweed-growing seashore areas in northern Japan.

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The harbouring behaviour of three species of cockroaches, Periplaneta americana, P. japonica, and Blattella germanica, was studied experimentally using rectangular paper-pipe shelters of 12cm×4cm×different heights (2cm, 1cm, 0.5cm) or those 3cm×2cm×different heights (1cm, 0.5cm). These shelters were placed side by side in a test container. The results of the experiments can be summarized as follows. I. Periplaneta americana and P. japonica : Single adults of these species preferred the height of shelters in a descending order of 1cm>2cm>>0.5cm, but the preference of single nymphs was 0.5cm>1cm. When tested at the same time, two adults, as well as two nymphs of the 3rd to 5th instar stage, tended to enter into separate shelters. The preference of 1st instar nymphs between 1cm and 0.5cm shelters was not so clear, but 1st instar nymphs were usually found in couples in either of the two shelters. These results indicate that the harbouring behaviour of the two species is similar to that of P. fuliginosa reported before (Tsuji and Mizuno, 1972 and 1973). II. Blattella germanica : The preference of single and two insects of this species may be expressed as 0.5cm>1cm in height of the shelters. However, considerable number of tested insects were found out of the shelters, suggesting that the harbouring behaviour of this species is somewhat different from that of the other two species. When three shelters of 2cm, 1cm, and 0.5cm heights were exposed to single adults, 90% of them were out of the shelters. While 75% congregated in 0.5cm shelter when 16 adults were tested at the same time. This density-dependent harbouring and congregating behaviour of adults may not be due to interattraction between two individuals, but to conditioning effect produced density-dependently in the suitable (0.5cm height) shelter, because two adults, when tested in the same container, were usually found in separate shelters or out of them. Two 3rd to 5th instar nymphs were usually found in separate shelters or out of them too. Two 1st instar nymphs, however, tended to coexist in one of the shelters.

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The investigation on the mosquito populations collected with the pig baited trap and the dry ice baited trap was carried out on the paddy field area of Natori City, Miyagi Prefecture during the three years, 1965-1967. The results obtained are summarized as follows : 1. Of all the trapped specimens, more than 99 percent belonged to the unengorged females of the following five species-Culex tritaenior-hynchus summorosus, Anopheles sinensis, Culex pipiens pallens, Aedes vexans nipponii and Armigeres subalbatus. 2. The species compositions show remarkable difference between the pig baited trap and the dry ice baited trap in relative abundance of Culex tritaeniorhynchus summorosus, Anopheles sinensis and Culex pipiens pallens. 3. After the peak of seasonal abundance the numbers of mosquitoes decrease abruptly in all the mosquito populations when sampled by the dry ice baited trap. This might be caused by the difference of the age structure of the mosquito population attracted by different kinds of baits. 4. The seasonal succession of the mosquito population structure is almost identical between both traps. However, Anopheles sinensis as dominant species in the population appears in the pig baited trap later than in the other. 5. Moreover, annually the seasonal prevalence of each species and the seasonal succession of the mosquito population structure changed considerably in the both traps.

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By topical application, Hokota strains was 63 times as resistant as susceptible NAIDM strain to diazinon, and 38 times to diazoxon. Resistance of Hokota strain to diazinon, on the other hand, was about 54 times, when the insecticide was injected. Acetylcholinesterase preparations from both Hokota and NAIDM strain were affected similarly by diazinon or diazoxon, in vitro. (In)_<50> values for acetylcholiesterase of both strains were respectively 8×(10)^<-7> M to diazinon and 4×(10)^<-10> M to diazoxon. By topical application of ^<32>P-diazinon, it was revealed that diazinon penetrated the integument of NAIDM strain more rapidly than that of Hokota strain. Consequently, greater quantities of chloroform extractables were found in the susceptible flies than in the resistant flies. Diazoxon contents in chloroform extractables in Hokota and NAIDM strain were 0.3 and 6.4%, respectively, which were equivalent to 0.20 and 8.77mμg/fly, 1 hr after topical application of 1μg/fly diazinon. The higher diazoxon level in susceptible strain, which was immediate cause of death in susceptible flies, seems to depend partly on rapid diazinon penetration through the integument, but mainly on the other mechanisms, such as lower rate of degradation of the insecticide.

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We have evaluated lethal activity of 19 synthetic juvenile hormone analogues against of Culex pipiens pallens. All tests were conducted in 300ml glass vessels containing 200ml of water provided with a small amount of food. Thirty of 3rd or 4th instar larvae were introduced into each vessles. Tested juvenile hormone analogues were mixed with 30% of a emulsifier, and certain amount of the mixture was added into the vessels to make emulsions with known concentration of JH analogues. The number of dead larvae and pupae were recorded daily until all test insects have emerged out. All compounds tested were characterized by their inhibition of pupation and adult development, but not by toxicological kill. With many compound tested at 10ppm a high percentage of the larvae gave rise to abnormal pupae resulting in their death. Compounds No. 17 and 19 were most effective in blocking adult development of the 4th instar larvae, giving (LC)_<50>'s as 0.04 and 0.03ppm respectively. The results are of special interest to control the mosquito larvae which has become resistant to all conventional insecticides, and as the alternative control agent of the conventional insecticides in respect of enviromental pollution.

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The redescriptions of the adults of Hirstionyssus apodemi Zuevsky, 1970 and Hirstionyssus tatricus Mrciack, 1958 and descriptions of the deutonymphs of both species were presented in this paper. Nippon-ashibuto-dani for the former species and Yachi-ashibuto-dani for the later one were proposed as the Japanese names of these mites.

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