The characteristics of spermatozoon of Culex pipiens pallens, have been observed by the electron microscope. The measurment of spermatozoon is approximately 220μin length and 0.6μ in maximum diameter of the whole body. The nucleus which occupies the anterior part of a spermatozoon, is the most electron dense. The nucleus is surrounded by a ring of a row of microtubules whose axis is parallel to the long axis of the cell. The minute plate-shaped head cap located in the anterior end, is about 130Å in thickness and about 0.5μin diameter. The posterior nuclear groove is connected to the axial filament complex which extends to the posterior end of spermatozoon as axis of the tail. The flagella has a 9+1 pattern in the filament of axial filament complex. Finally, the characteristic pattern of these filaments is lost and the filaments disappear at the posterior end of the spermatozoon. The small centriole-like body abuts on the posterior end of the nucleus but in this observation no small body could be identified. Two cords of mitochondria extend along the axial filament complex from the posterior end of the centriole like body towards the posterior end of the spermatozoon.

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An ecological study was made on the larval populations of mosquito overwintering in Kagoshima City, southern Japan. The purpose of this report is to show the mode of overwintering habits of several mosquito species from the view point of seasonal change in population size and larval age structure. 1) Larvae of Uranotaenia bimaculata, Aedes japonicus and Tripteroides bambusa survived winter season, and their population size increased during winter months with appearance of the younger larvae and reached to a maximum in January, February and April, respectively. The older larvae and pupae became dominant in spring months, when a considerable number of pupal exuviae was observed. These facts apparently indicate that eggs of these species hatch in the course of overwintering and that the first adult populations of the next year originate mainly from the newly hatched larvae. 2) Population size of Armigeres subalbatus diminished gradually from December to March. Through these months, only the fourth stage larvae were observed except in March, when a number of pupae appeared. The larval population became extinct in April and a small number of pupal exuviae remained. These indicate that the fourth stage larvae survive the coldest months and pupate in March and that adults emerge in spring months. 3) Population size of Culex pipiens s. l. diminished gradually from December to March. During these months, however, a number of the fourth stage larvae grew to pupae and a few pupal exuviae were observed. Early in April, population size reached to a maximum with appearance of the first stage larvae, which hatched from the egg masses newly laid in March. These indicate that most larvae and pupae become extinct during the coldest months, even if a few of the pupae emerge into adults. So, the first adult population must be originated from the newly hatched larvae. 4) None of Aedes albopictus larvae and pupae was observed in the coldest months. The first population of younger larvae started in March and older larvae became dominant in May, when a considerable number of pupae and pupal exuviae were observed. These show that this species can not survive the coldest months as larvae and that the first adult population originates from the newly hatched larvae.

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From April to October 1967, some ecological surveys and experiments on Culex tritaeniorhynchus summorosus were carried out with wild-caught mosquitoes, which were collected by light trap method in a pigpen and a neighbouring henhouse in the suburbs of Yokohama. The collections of the mosquitoes have been done successively for the whole night every day. Throughout the experiments, all developmental stages of the mosquitoes have been reared in a room under the conditions of room temperature and natural day length, without any heating or cooling and lighting. The average bloodsucking rates of the female populations were calculated as 59.0% in the pigpen and 22.3% in the henhouse. In the former, however, the rate in July was below average (45.7%) owing probably to the whole sprayings in the pigpen. In rearing cages, the ovipositing activities of engorged females collected every month in the pigpen could be seen successively from the end of May to September and, in September, the ovipositing rate was higher than that in the preceding months, being more than 50%, especially 70% in early September. No females laid eggs in April and October. The average egg number of about 300 rafts which were laid during the period from June to October was checked. In June, 227.5 eggs per raft was counted and this was the highest throughout the seasons. From this month, a gradual reduction in the number of eggs was noted during the following four months, namely 195.7, 185.5, 177.3 and 148.6 eggs per raft respectively. The hatcheabilities of these egg batches were comparatively uniform, 95.1% in the average rate. The parous rate of the female population in the pigpen was almost similar to that in the last year, 1966. The rate was the lowest in May and it increased gradualy toward the end of the season and, in October, the population consisted mainly of parous females, being the rate 89%. This shows that there was a just reverse relationship between the parous rate and the average egg number in seasonal prevalences. A dissociation of ovarian development of F_1 females developed from the engorged wild mosquitoes which were collected in the pigpen were observed after a feeding on mice from June to October. The first gonotrophic dissociation was recognized in some individuals (11.8%) emerged at the beginning of August when the threshold of day length was about 14 hrs. Since the mid-September, when the length of day was 12 : 30-12 : 20 hrs, those individuals rapidly increased, more than 80% in the rate of gonotrophic dissociation. However, when the mosquitoes have just started larval developments, the thresholds of photoperiod should be larger than those given above. According to these results, it was quite probable that the hibernating adult population involves the following two groups of mosquitoes : 1) some individuals of gonoactive generation developing during the period from September to October, 2) all individuals of gonoinactive generation derived from the former during the same periods. The latter should be the main hibernating mosquitoes in general.

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The ecological studies of vector mosquitoes of Japanese encephalitis virus were carried out in the suburbs of Izumi City, Osaka Prefecture, since 1963. Mosquitoes were collected by nets and sucking-tubes at a cow-shed and by dryice baited traps in paddy fields. 1. The most abundant species was Culex tritaeniorhynchus, which was over 90% of all collected. There was no significant difference in species composition between mosquitoes collected at the cow-shed and those in the paddy fields. 2. Major occuring season of the Culex tritaeniorhynchus is in July and August by counting the number of mosquitoes collected by the light trap of New Jersey type, but peak of emergence of this species varied both from place to place and from year to year at the cow-shed during three years (Fig.3). 3. Observations of the mosquitoes breeding in the paddy fields were made in 1965. Culex tritaeniorhynchus was the dominant species, and a few other species were also found ; Anopheles hyrcanus sinensis (3.4%), Culex pipiens pallens (2.3%) and Culex vishnui (0.09%). Seasonal prevalence of immature mosquitoes is shown in Fig. 7. Culex tritaeniorhynchus appeared in the beginning of July, reached the peak in the middle of the same month, and disappeared in the end of August. 4. Blood-sucking rate of C. tritaeniorhynchus collected inside the cow-shed was examined. The seasonal change in the blood-sucking rate of this species is shown in Table 3. The rates were 74 to 97% during the period from the middle of July to the beginning of August. Although the rate decreased slightly in the middle of August, it was kept on the level of about 50% until the end of September. Mosquitoes collected in April were presumed to belong to a overwintered population, and the blood-sucking rate of this population was shown to be about 50 per cent. Later, the newly emerged mosquitoes began to appear in the middle of May, and the rate became low suddenly. 5. Observations of the swarming of Culex tritaeniorhynchus were made near the cow-shed in 1965. The swarming was formed usually at a height of 3 to 5 meters. The seasonal change in the sex composition of the swarms of Culex tritaeniorhynchus is shown in Table 4. The percentage of males to the total number was in the range of 24 to 59 from the end of July to the middle of August, and thereafter, the male rate became higher. In the end of September, in spite of the absence of females, the males still continued to swarm. 6. Physiological age was determined for each lot of specimens according to Detinova's method. The species collected at the cow-shed were compared with those collected by the dry ice-baited trap in the paddy field. The parous rate of mosquito population collected inside the cow-shed was higher than in the paddy fields. And also, the rate of mosquito population collected inside the cow-shed was higher than that collected outside. The parous rates of the fed and unfed females collected inside the cow-shed showed no difference. 7. Seasonal changes in the age composition of the mosquito population were observed. Considering the seasonal changes in the parous rates, it was suggested that the adults appeared at first at the middle of May, and that the adults of the last generation appeared at the beginning of September. 8. Virus isolation from the females of Culex tritaeniorhynchus was carried out during 1963 to 1966. As shown in Table 6, the isolation rate of mosquitoes collected in the cow-shed was higher than that in the paddy field. The time of appearance of the infected mosquitoes varied from year to year. Since the size of the human epidemics may depend largely on the population density of the infected mosquitoes, the density of mosquito population during the period of the virus-amplifying cycles was suggested to be a critical factor for the epidemic size.

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Larvae of a sarcophagid fly Parasarcophaga harpax (Pandelle, 1896) were collected from a one day old new-born female in Tokyo, causing otomyiasis. This is a new report of otomyiasis in Japan since 1945, and the first report of the disease caused by this species of the fly. Of three larvae collected from the patient and kept in saline, one was mounted on a slide and two were cultured in horse meat. One male and one female adult flies emerged and both were identified as the above species. The patient was born in a women's hospital on 25 June, 1968, and her mother recognized three larvae coming out of her year in the next morning. At the examination by a phisician in the same afternoon, three more larvae were found in the outer auditory canal, and two other larvae were seen in the tympanic cavity through a hole on the tympanic membrane. Detailed descriptions and discussions were made on the clinical signs observed, and the taxonomic status of the specimmens of the fly obtained from the patient. This case is noteworthy in that she was only one-day old newborn, and that the species of the fly was new as a cause of myiasis.

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The repellency fo the commercial pyroligneous liquors was observed against the flies gathered on meat and the slugs. Also the toxicity of commercial pyroligneous liquors was examined against the slugs. The results obtained were summarized as follows. (1) Flies averted odours of neutral, basic and phenolic fractions of the pyroligneous liquor set aside fish meat. The repellency of mixture of these three fractions is more effective than each single fraction. The sun-drying fish treated with the above mixture is tested the repellency to flies. (2) The pyroligneous liquors and the liquors adjusted pH with alkaline showed both marked toxicity on the Japanese native slug, Incilaria confusa Cockerell in contact tests. Organic acid and carbonyl fractions of the above liquors showed more effective to kill slug than basic, neutral and phenolic fractions. (3) Slugs averted odours of the pyroligneous liquor.

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As reported in a previous paper (1965), growth of the housefly larvae (Musca domestica vicina) seems to be greatly affected by pH value of rearing media. To clarify the relationship between pH value of the medium and growth of the housefly larvae, a series of experiments, in which egg, 1st, 2nd and 3rd instar larvae were transplanted and reared in the media of various pH, was carried out. PH value of the medium was adjusted by addition of hydrochloric acid, oxalic acid, caustic soda and ammonia water to basic medium (moistened "Dry mixed food for rat and mouse"). The oviposition rates on hydrochloric acid media were also observed. The results are summarized as follows : 1) In the media of which pH value was 5 to 10, the larvae grew normally, giving high emergence rates. In the pH value of less than 5 or more than 10, larval growth was remarkably disturbed, particularly in acidic side. 2) Emergence rate of the housefly on the hydrochloric acid medium varied with developmental stages of the inoculated larvae. The last instar larvae were more resistant to the acidic media, but about 50% of these larvae could become to adult without any food. 3) It was observed that the houseflies undout-edly refused laying eggs on highly acidic media.

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[in Japanese]

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