1. In the late spring of 1968,nuisance and biting problems by an unusually great number of adult mosquitoes took place in a suburban area of Kagamigahara City, Gifu Prefecture, Central Japan. Through a request of the city authorities, a series of field investigations were made on the population dynamics of the pest mosquitoes. Chemical and environmental control measures were also planned. 2. A pool which was receiving most of the raw wastes of a starch and woolen factories was found to be the main breeding source of the bothering mosquitoes. This pool was located at the river beach neighboring the residential quarter and had an extent of approximately 80 ares and an average depth of 0.2 meters. Population density of mosquito larvae and pupae at the station P selected in the pool was estimated by the removal method, and age structure of these aquatic stages was also analyzed. Imaginal population size in the residential district about 200 meters apart from the breeding source was estimated with light trap collections. These investigations were continued on the weekly basis during the period from June to November, 1968. 3. As the results, it was known that the overall species composition of mosquitoes of this area was very unusual for such a typical suburban habitat surrounded by many paddy fields; more than 90 percent of the collected adults and larvae were the house mosquitoes, Culex pipiens pallens Coquillett. This uncommonness was further ascertained by the comparison with the results of our mosquito surveys simultaneously performed in other two areas with similar topographical features. For the correct identification of the species, examinations were made of ommatidial number in females as well as DV/D value in males randomly sampled from the above "C. pipiens pallens" population. The results revealed that the autogenous house mosquito, C. pipiens molestus, was not intermixed. 4. Population dynamics of the C. pipiens pallens was studied by analyzing the seasonal change of larval population size and age structure. It was presumed that the adults had four definite peaks of emergence in late June, mid and late July, and early August on the bases of precursory ageing in the larval population. The actual number of adults collected by light traps and the above presumption were proven to be in good agreement. 5. Details of the control measures taken to cope with the outbreak were described, and several problems in the planning of insecticide application along with the merit and demerit of the environmental control of the pest mosquitoes, particularly of the construction of drainages, were discussed in relation to the pollution of inland water.
Using the Tullgren funnel method, we surveyed for trombiculid larvae around dwellings and in mandarin orange groves on the slopes of Sengenyama and Maruyama, Yamakita Town, Kanagawa Prefecture, Japan, during the period between 8 October 1992 and 8 January 1993. In total, 6,690 trombiculid larvae, consisting of 6,669 Leptotrombidium scutellare (Nagayo, Mitamura, Tamiya & Tenjin), 13 L. fuji Kuwata, Berge & Philip, two L. himizu (Sasa, Kumada, Hayashi, Enomoto, Fukuzumi & Obata), two Neotrombicula japonica (Tanaka, Kaiwa, Teramura & Kagaya), one Gahrliepia saduski Womersley, and three Walchia ogatai Sasa & Teramura, were taken from 240 soil samples (40 samples, six times at intervals of 2–4 wk). From the above species composition, L. scutellare is suspected to be the sole vector of scrub typhus in the survey area, where the disease is known to be caused by two serotypic strains of Rickettsia tsutsugamushi Ogata, Kawasaki and Kuroki. L. scutellare larvae rapidly increased in number in late October to form an acuminate peak of abundance in early November, followed by a gradual wane.
Based on the previous data (Uchikawa et al., 1994), we presumed that Leptotrombidium scutellare larvae were distributed widely in man-made environments around densely populated areas inwestern Kanagawa Prefecture, Japan. Employing modified Suzuki's visual sampling method (Uchikawa et al., 1993), this assumption was examined during the period between November 4 and 6, 1993, in Yamakita Town and Minamiashigara City, Kanagawa Prefecture. The above assumption was verified, indicating at the same time that the method was appropriate for our purpose. Many L. scutellare larvae were frequently found on shaded and humid places but not on dry soil surface. Very heavily infested places were encountered in mandarin orange groves and, unexpectedly, in a young kiwi fruit orchard surrounding the center of Yamakita Town with crowded dwellings, and in mandarin orange groves on gently rolling hills of Minamiashigara City. As many as 9, 658 unfed larvae to use in other analyses were taken on sampling and collecting pieces of black cloth during the survey. These larvae were observed to have stayed still in clusters on the cloths sealed in plastic bags that had been kept in a container since the previous day.
A case-report of oral-stings by spermatophores of a squid, Tadorodes pacificus was described. The male patient was one of the authors of this report, aged 26 years, who was injured in his oral cavity immediately after eating uncooked internal-organs of a squid by mistake. He complained of severe pain and foreign-body sensation in the oral cavity. On examination, more than 15,small spindle-shaped stings stuck in mucous membrane of the tongue, soft palate, and upperlip. Stings were removed surgically in hospital, and they were identified as squid spermatophores by their shapes and containment of sperms. In addition to this case, two other cases with similar symptoms were identified as oral-stings by squid spermatophores. These cases suggest that fresh squids should be carefully prepared before eating them as "sashimi" or in raw.
