[in Japanese]

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A study of the control has been made on Warfarin for house-rats in specified area. The chemical is consumed most by animals 3-4 days later, and dead animals are found most 6-7 days later baiting. Graphically the curve of consumption is parallel with that of the number of fatality. It implies that the baiting of this chemical must be carried out over rather a long period.

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1. Mosquitoes were collected by a New Jersey type light trap throughout a whole year from May, 1952 to April, 1953 at the backyard of Yasui Primary School, Uzumasa, Ukyo-ku, Kyoto, Japan. 2. The station where the trap was set locates on the boundary zone between the town area and the cultivated land, and is surrounded by rice-fields except on the north side which is crowded with houses. 3. The whole night sampling which was made 41 times during the period mentioned above yielded 8, 655 individuals classified into 5 genera including 19 species. 4. Of the species obtained, Culex pipiens (32.6%), Culex tritaeniorhynchus (29.0%) and Anopheles sinensis (26.0%) are outstandingly large in individual number, while such species as Culex vishnui (9.0%), Culex bitaeniorhynchus (1.4%), Culex rubithoracis (0.7%) and Armigeres subalbatus (0.4%) constitute, though rather small in number, components which cannot be ignored. The other species are less than 0.1%. 5. Culex pipiens : Wintering females are captured scatteringly in March and April and males appear from about the middle of May. Then mosquitoes are captured almost continuously till the end of November. This species has, therefore, the longest interval of activity, the maximum occuring towards the end of June. 6. Culex tritaeniorhyncus : Females first appear towards the end of May and males in the middle of June. There is the maximum about the end of July and sudden disappearance late in September. 7. Anopheles sinensis : Females are captured scatteringly in March and April and males first appear in the middle of May. An abrupt increase in number is seen early in July and disappearance early in October, the maximum being attained towards the end of July. 8. Culex vishnui : Females appear late in June and males early in July. There is the maximum in the middle of August and disappearance about the end of September. 9. Culex bitaeniorhynchus : Females are captured first early in June but not for about a month that follows. This species is seen almost continuously from the middle of July to the end of September, the maximum being attained toward the end of July. 10. Culex rubithoracis : This species is captured by small numbers almost continuously from the middle of July to the middle of September. Males become considerably large in number during the later part of October. 11. Armigeres subalbatus : This species is captured from the end of August to the middle of October. The largest numbers were obtained about September 20. 12. The other species were obtained only discretely by small numbers and it is difficult to describe definitely the general modes of seasonal variation. 13. There are appreciable differences among the periods of maximal appearance of various species, and, on the whole, there seems to be a tendency of species to segregate seasonally their appearance. 14. Comparing the present results with those that have been hitherto published, it is concluded that the seasonal variation of appearance in the adult mosquitoes may differ under different environmental conditions around the station and by different methods of sampling, and that it cannot be interpreted in terms of the latitude or climate. 15. Since investigating the seasonal variation of the mosquito population aims ultimately at finding out the causal relation between it and the seasonal variation of the environmental factors, the latter should be approached not through summarizing the common aspects but through analysing the different features of succession obtained of each species by different methods and at stations of different environmental conditions. 16. In addition, general methodological consideration was made on the light trap sampling.

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In the summer of 1954, the observation on the diurnal rhythmic activity of the unattached larvae of Trombicula akamushi (Brumpt, 1910), the vector of Tsutsugamushi disease, was made in a certain wood along the Omono River in northwestern Honshu, Japan. The number of the mites crawled up on nine black bakelite-plates, which had been set on the ground surface two days before the observation, was counted every hour for 37 and 11 consecutive hours. Four counts were made in each hourly observation at intervals of five minutes. According to the results, the mite count was the highest at 3 : 00 or 4 : 00 P.M. and a less inconspicious increase was seen at 11.00 A.M. In the night time from 7 : 00 P.M. to 6 : 00 A.M., the mites seemed to be much less active than in the daytime. Such environmental factors as the air temperature and the relative humidity 2cm above the plate, the soil temperature 10cm beneath the soil surface and the light intensity on the plates were measured at each time of the counts. It was revealed that the number of the mites observed on the plates showed significant positive correlation to the soil temperature or the light intensity, and significant negative correlation to the relative humidity, but that between the number of the mites and the air temperature was not significant. Among the numbers of the mites in four counts at each observation, the first counts were usually the lowest, and was the highest the last counts. The difference between average numbers of the first and the second, and that between the second and the third were statistically significant, but that between the third and the fourth was not significant.

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To make investigations on the repellents against rats (Rattus norvegicus var. albinus), we tried to experimental repellents of rats with several chemicals : 1. γ-BHC (crystal)-Ortho-DichloroBenzene mixed solvent has made the most effective to their repellents in the case of using trial chemicals this time (after solving γ-BHC of 20g. into acetone of 70g., 20cc. ortho-dichlorobenzene together with 1cc. eugenol added to the above and it was made of 100cc. in total quantities). 2. Mixed chemicals composed of 1.8l. creosote, 400g. naphthaline and 180cc. gasoline, being used for hare's repellents in general are shown effectivelly against to the most.

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The murine lice in Japan known untill May, 1955 were composed of nine species belonging to two genera; they were Polyplax spinulosa, P. serrata, P. abscisa, P. reclinata, Hoplopleura affinis, H. acanthopus, H. oenomydis, H. longula and H. intermedia. As for the hosts of these lice, ten species of rodents and Suncus murinus, which belonged to the family Soricidae, were recorded. Host-parasite relationships, records of specimens and brief differential descriptions, together with a key to these Japanese lice were given in this paper. Although the characters of paratergal plates were fairly different among the three groups of specimens collected each from Microtus montebelli, Eothenomys smithii smithii and Clethrionomys rufocanus bedfordiae, the author, for the time being, identified all these speicmens as Hoplopleura acanthopus. Hoplopleura oenomydis collected from Rattus rattus in Honson, Nijima-island, Honshu, provided with the very larger spiracles on paratergal plate than those of the specimens collected from other places in Japan. Hoplopleura akanezumi Sasa, 1950 was included in Haplopleura affinis in this report, because these two species related very closely in many respects except for the slight difference of convexity on the process of sternal plate. Pending problems described above will be cleared in future when the author is able to obtain more specimens.

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Using small model pots, the effect of various insecticides was observed against the fly-maggots which are the main pest in the excrement-pot of our native-type lavatories. The result agrees rather well with the one obtained by a careful practical test which is an extremely laborious work. The obtained dorsage-mortality regression line was examined to be satisfactory by x^2 test. The effective concentration for ortho-dichlorobenzene emulsion was revealed to be 50-100 times dilution of the original emulsion, and for lindane 200-1000 times. If the dosage is sufficiently high, o-dichlorobenzene emulsion, lindane emolsion, lindane-o-dichlorobenzene mixed emulsion and linda ne powder have nearly equal efficiency. In a highly diluted concentration lindane emulsion still shows a high efficiency. It was also confirmed that the effectiveness is strongly influenced by the condition of the excrement, that is, whether it is liquid or solid, as well as by the amount of used toilet-papers in the pot. So far as a practical effective dorsage of the emulsion is concerned the maggots fled from the pot due to the stimulation of the emulsion were considered to be negligible in considering the mortality of maggots. A practical effective concentration should be decided by a careful examination of the condition of each lavatory.

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The experiments on the effect of o-dichlorobenzene emulsion against the larvae of Sarcophaga spp. were carried out in the laboratory and in the pots of lavatories comparing to that of lindane emulsion. As presented by Toyama and Suzuki (Botyu-Kagaku, 19, 115-121, 1954), lindane was effective in higher dilutions than o-dichlorobenzene by such method in the laboratory, but the latter chemical had a comparatively high insecticidal efficacy. In the present experiments, the test insects (3rd instar larvae of Sarcophaga peregrina R.-D.) dipped in the emulsion of the chemical for 24 hours were kept in the other petri-dishes till some of them pupated and emerged, and the number of pupae and emerged adult flies were counted. In the experiments of lindane emulsions, the retarted lethal effect was sometimes seen in the advanced stages, some larvae being incapable of forming pupae, some pupae died in situ, or newly emerged adults were seen to survive only a few days. In o-dichlorobenzene or DDT, such retarded effects were not observed. In the experiments in the petri-dishes, the action of o-dichlorobenzene was more rapid than that of lindane so far as the sign of intoxication of the larvae appeared. However, the lethal action of the latter chemical was more rapid than the former. Through the field experiments, the standard amounts of the insecticides required for the practical control of fly larvae in the lavatory pots were concluded as follows : o-dichlorobenzene emulsion, 2 liters of 30-100 times dilution per square meter; lindane emulsion, 2 liters of 100-300 times dilution per square meter. It was also observed that the more the contents of the pots were solid, the larger was the amount of the insecticides required.

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[in Japanese]

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[in Japanese]

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In the present papers, the authors report on the new findings pertaining the ecology and the mechanism of attaching to the hosts of the unengorged larvae of Trombicula scutellaris Nagayo et al., the vector of Shichito-type Tsutsugamushi disease or winter-autumn scrub typhus. In Hachijo Isiand, they were found to appear on the surface of rocks forming large patches soon after the observers approached. Through the laboratory experiments using models (corn made of Plaster of Paris, trianglar paper, etc.), the larvae sho-wed negative pboto and geotaxis and stayed still forming a cluster near the top and opposite to the light when they were not stimulated. Then, an important fact was discovered that the resting larvae were immediately stimulated by the exhalation of human or rats and began to move around the top until they attached to the hosts or rested still in the original position after about half an hour. The factor in the exhalation to stimulate the larvae was certified to be certified to be carbon dioxide, as it was absorbed by alkali and the same effect was exhibited by the application of the air containing up to about 0.000008% of chem ically prepared carbon dioxide.

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