The incidence of Japanese encephalitis (JE) in Japan has decreased in recent years as a secondary consequence of modernization of the agricultural system in this country. The population of the vector mosquito, Culex tritaeniorhynchus has decreased in ricefields where new methods for rice cultivation have been applied. Nowadays, ricefields have small amounts of water due to technology which controls the management of intermittent water supply, new varieties of rice have been developed to shorten the period of cultivation, and pesticides are extensively used. These facts have transformed the ricefields into inadequate places for mosquito breeding. The following reasons also contribute to the drastic reduction of the vector mosquito with consequent decrease in incidence of JE : very few teams of animals are raised in the farms, the large-scale pigsties are located far from human habitation, and modern construction methods of houses and pigsties hamper the entrance and feeding of mosquitoes. Recently, projects for development of ricefields and pig breeding are promoted in Southeast Asia with the purpose of increasing food production. Such promotion is giving rise to spread of JE in Southeast Asia and this is, therefore, imported to Japan. Moreover, the global warming, the changes in environment and emergence of insecticide-resistant mosquitoes increase the risk of epidemic in Japan and other Asian countries at any time. Therefore, the development of additional methods for vector control and strengthening of the alert attitude by health professionals and scientists are needed.

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This study shows the effectiveness of house modification for the control of Chagas' disease vectors in natural and artificial conditions. Wall plastering and paint were evaluated for the control of population of Chagas' vector by assessing vector numbers in man-hour collection before and after modifications in 1993. We evaluated 29 houses, from three small villages in Villa Canales, located in the Department of Guatemala; eighteen of them had some kind of modification or improvement. In the houses covered with plastered of cement and lime, we found a 92% reduction of the total vector population in the following year. Other houses with partial modification and paint with lime showed a reduction of 53% and 35%, respectively. In houses without improvements, the number of vectors remained the same. We collected Triatoma dimidiata Latreille (1911), and T. nitida Usinger (1939) in the houses; the infection rate with Trypanosoma cruzi was 21% and 50%, respectively. After the house modifications no significant changes occurred in the parasitic ratio. There was no statistical difference in longevity of T. dimidiata when kept in artificial conditions (simulation of wall plasters) compared to research in the fields.

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The number of Triatoma dimidiata found per man-hour of collection in each of the three mud-walled houses were 4,1 and 37. In the third house 8 of T. nitida were also collected. When the walls of these houses were dismantled, an additional 114,141 and 307 of T. dimidiata were collected along with 34 of T. nitida in the third house. In the palm-thatch roofed huts only Rhodnius prolixus were collected. The numbers per man-hour collected were 11,27 and 26. When the roofs were dismantled and searched 75,449 and 978 bugs were found in the respective houses. These results indicate that the numbers collected by the traditional method did not accurately reflect the population density in the houses. The collections indicate that the hiding places of T. dimidiata and R. prolixus were very limited within the houses. An average of 31% of T. dimidiata were collected in only two dismantled block sections (2m^2) which were close to the beds and chicken nest and 40% of R. prolixus in the last house were obtained in the lower section of the palm-thatched roofs just above a bed. This area occupied only 4.2% area in total space of the house. These results suggest that insecticidal treatments would be most effective if they focused on the places where more bugs concentrate.

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When a harbourage shelter occupied by marked cockroaches was placed in one of two compartments divided by a partition with a small hole through which the cockroaches could come in and go out in a test container, and another new and vacant shelter was placed in the other, the movement frequency of male adults from one compartment to the other was much higher than that of female adults. The movement frequency of male adults increased with the increase of population density more sensitively than that of female adults. When female adults were released into a test container where only one shelter fully occupied by male adults had been placed, most of the male adults in the shelter were replaced by the female adults within 10 minutes. Female adults having fully occupied a shelter, however, were not replaced by introduced male adults. These results indicate that female adults prevail over male adults in their interaction for a suitable harbourage space, while male adults tend to seek new space more actively than female adults.

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More than 2 thousand field-collected specimens were morphologically examined to clarify the taxonomic status of Anopheles saperoi saperoi and An. saperoi ohamai. No specific or subspecific difference was detected between the two subspecies in the larval and pupal chaetotaxy. Anopheles s. saperoi reared under low temperature and short day-length (15℃, 10h) in the larval stage had longer wings, longer subcostal pale spots and shorter apical pale spots than the ones reared under high temperature and long day-length conditions (25℃, 15h). These variations also were confirmed in both subspecies obtained in the fields at various seasons. We consider that the differences in the subcostal and apical pale spots between these two subspecies are due to seasonal variation occurring in both subspecies. Thus, An. ohamai is degraded to a mere synonym of An. saperoi.

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Parasitological and histopathological examinations were carried out on 13 wild raccoon dogs, Nyctereutes procyonoides, having severe dermatitis captured in Tomioka-Kanra district, Gunma Prefecture. All of the raccoon dogs examined were infected with a great number of Sarcoptes scabiei, but not with Demodex. Histopathological examinations of the autopsy specimen demonstrated prominent hyperkeratosis, acanthosis and papillomatosis and numerous cross-sections of S. scabiei in the horny layer. S. scabiei were considered to be the cause of the dermatitis of these wild raccoon dogs.

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Neopeace^<(R)> adhesive was evaluated for trapping synanthropic flies at a garbage dumping ground in Malaysia. Majority of fly species were trapped by the adhesive compared to the fly traps (P<0.001). Thus, the adhesive could be utilised in fly control programmes.

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Anopheles minimus larvae from Ishigaki Island, and An. saperoi and An. sinensis larvae from Okinawa Island, Okinawa Prefecture, were tested for insecticide susceptibility. The LC_<50> values of organophosphates (malathion, fenitrothion, dichlorvos and temefos) examined were low for An. minimus. Against p, p'-DDT, 6 organophosphates and permethrin tested, An. saperoi showed low LC_<50> values. For An. sinensis, the LC_<50> values to 5 of 7 organophosphates were high, being 19.2ppm to malathion, 15.5ppm to fenitrothion, 9.7ppm to dichlorvos, 8.3ppm to diazinon and 73.0ppm to trichlorfon, respectively. Furthermore, the values were high to p, p'-DDT and permethrin.

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Lucilia bazini Seguy is newly recorded from Peninsular Malaysia based on a male specimen preserved in the Zoological Museum of Copenhagen University. A revised key is provided with all Malaysian species (7 spp.).

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A collection of larvae and pupae of Simuliidae (Diptera) made for the first time on Iki Island, Nagasaki, Japan, in March 1998,has disclosed the breeding of the following six blackfly species : Simulium (Simulium) aokii, S. (S.) arakawae, S. (S.) bidentatum, S. (S.) nikkoense, S. (S.) rufibasis and S. (Nevermannia) uchidai. Also, one female adult of S. (N.) uchidai was collected by a hand net on Tsushima, an adjoining island, representing the first record of this species from this island.

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The effects of photoperiods on host-feeding and development in Haemaphysalis flava nymphs were observed at 25℃ under four different photoperiods (10L-14D, 12L-12D, 14L-10D, and 16L-8D). The rate of engorgement was significantly reduced by exposure to 10L-14D or 12L-12D photoperiods from the egg to the unfed nymphal stages. The development of the engorged nymphs was also retarded or arrested by exposure to 10L-14D or 12L-12D photoperiods. These results suggest that diapause occurs in the unfed and engorged nymphs that have been exposed to short-day or 12L-12D photoperiods from the egg stage. However, the rate of engorgement of the nymphs was relatively high when they were reared under a short-day photoperiod of 10L-14D. In addition, evidence of commencement of apolysis (the developmental change in the cuticle) was found in the engorged nymphs at a 10L-14D photoperiod. Thus, the diapause of the nymphs appears to be light. Although the diapause of H. flava nymphs is light, most of those that are molted from the engorged larvae in autumn may not develop to adults within the same year.

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