In order to evaluate the blackfly control, the comparison was made for the efficacy of the CO_2-traps with 2kg of dry ice or with the different discharge rates of CO_2 gas (250,500,1,000,2,000ml/min). Mini-CO_2-traps with 1kg dry ice operated by battery were also tested for the collection of the blackfly, Simulium ochraceum, in the endemic area of onchocerciasis in Guatemala. The species composition of adults collected with the CO_2-traps was similar to that of larvae from the nearby breeding place. The number of blackflies collected by the CO_2-traps varied greatly with discharge rates of CO_2 gas. Seasonal trends of blackfly density obtained by the CO_2-traps at the rates of 1,000 and 2,000ml/min and dry ice were similar to each other. But the traps with less than 500ml CO_2/min didn't produce satisfactory results to demonstrate the trends. The species composition by the mini-CO_2-trap was similar to that by a human bait catch, but the number of blackflies by the former was less than one tenth of that by the latter.

View full abstract

Microencapsulated diazinon (MC) showed superior residual effect to emulsifiable concentrated diazinon (EC) against the German cockroaches. The observation of the body-cleaning behaviour of cockroaches, the chemical analysis of diazinon and the microscopic observation of the MC proved the easy attachment of the MC to their body surface and the massive ingestion into their digestive tracts. Thus, the MC in the guts of cockroaches plays an important part of its killing activity as the MC on the body surface does. Due to this bimodal entry, the short-contact and residual toxicities of MC are fortified over that of EC.

View full abstract

In the last several years, the number of tsutsugamushi disease (scrub typhus) patients began to increase throughout the mainland of Japan, not excepting Aomori Prefecture in the northern district. By analysing the data on distribution of chiggers, the outbreak of cases, and the isolation of Rickettsia in Aomori Prefecture, the author discusses the epidemiological aspects of the new type (spring and autumn type) tsutsugamushi disease, in which species other than Leptotrombidium akamushi (Brumpt) play the role of vector. Including the data from Sasa (1956) to the author (1979), 3 sub-families, 9 genera and 28 species of chiggers have been recorded in Aomori Prefecture. Of these, L. pallidum (Nagayo et al.) is one of the dominant species, and it is distributed widely and shows the peaks of occurrence both in spring and autumn in this district. After finding a suspected case reported in 1961,15 cases were found in Aomori Prefecture during the years 1971-1981. These cases were limited in spring and autumn, and some regions (Noheji, Shichinohe, Sannohe and Namioka). This led us to a new understanding of the "noxious areas" in this district. Strains of Rickettsia tsutsugamushi (Rt) were isolated from rodents trapped at the restricted locations in the Noheji and Namioka regions where patients had been infected. Especially in Namioka, where a lethal case occurred, the Rt positive rate in rodents was as high as about 57%, and one series of L. pallidum recovered from a Rt positive rodent was positive for Rt. The above observations suggest firmly that L. pallidum plays the role of vector of the new type tsutsugamushi disease in the noxious areas in Aomori Prefecture.

View full abstract

In the screening for insecticidal antibiotics with mosquito larvae (Culex pipiens pallens) as a test insect, the author isolated Streptosporangium albidum strain (TI-1) that produced a substance with highly insecticidal activity. From the results of the examination on cultural conditions for producing the larvicidal antibiotic in vitro, the dilutions of the culture filtrate of 1/8,000-1/10,000 to kill 50% of 1st instar larvae were considered as an extremely active titre. It might be supposed that the antibiotic has not contact insecticidal ability but stomach toxicity, because it was inactive against the mosquito pupae.

View full abstract

High, intermediate and low transmission efficiencies for Japanese encephalitis virus were differentiated among 7 colonized strains of Culex tritaeniorhynchus from different geographical areas when they were infected with a large dose of virus and incubated at 30℃. Two strains from Japan (Amami and Nagasaki) were highly efficient transmitters. One strain from Japan (Kyoto) and another from Taiwan were intermediate transmitters. Three strains from Pakistan were susceptible to JE virus, but their transmission efficiency was low. When mosquitoes were fed with a small virus dose and maintained at 25℃, salivary gland infection rates and transmission efficiency were low in the intermediate and the low transmitters. Susceptibility to virus infection and ability of the mosquito to transmit virus seem to be regulated by independent genetic mechanisms. The role of susceptibility of each secretory part of salivary glands on transmission efficiency of mosquitoes is discussed in connection with the geographical distribution range of JE virus in Asia.

View full abstract

An ecological study was carried out on distribution, movement and change in the body weight of Culex pipiens pallens Coquillett during their overwintering. Overwintering population of Cx. p. pallens was distributed aggregatively in a cave (air-raid shelter). More mosquitoes were found in the inner room of a 3-room shelter and gathered on the lower part of the wall. The degree of such aggregations changed with fluctuation in the temperature and humidity inside the room, and became maximum in January. The movement of mosquitoes was influenced by air temperature : It was least frequent in February when the temperature was lowest. The movement was least frequent on the lower part of the wall. The mobility rate (percentage of mosquitoes which changed their resting positions) was about 70% on average. Mean body-weight of mosquitoes before and after overwintering was 1.271mg and 0.708mg, the reduction rate being 44.3%.

View full abstract

Atylotus kakeromaensis n. sp. is described based on the materials from Amami-oshima Islands, Japan. This species is easily distinguished from other related species by the slender middle callus on frons and the light yellowish orange abdomen with an indefinite darker median stripe.

View full abstract

Hybomitra takahasii, n. sp. is described based on specimens collected in Hokkaido, Japan. This species is closely allied to Hy. bagheera Violovich recorded from Sakhalin, but differs from it by the black hairs on palpal segments and on abdominal tergites.

View full abstract

The biological activity of methoprene (Isopropyl (2E, 4E)-11-methoxy-3,7,11-trimethyl-2,4-dode-cadienoate) and its slow-release formulation, Altosid[○!R] 10F which contains 10% methoprene, were evaluated against the chironomid midge, Chironomus yoshimatsui Martin et Sublette in both the laboratory and the field. The biological effects of Altosid[○!R] 10F on C. yoshimatsui were similar to those on mosquitoes, resulting in pupal death, failure of emergence and abnormal adults. However, it was a unique phenomenon that pupation was inhibited at higher concentrations in chironomids as compared with mosquitoes. The IC_<50> values of methoprene and Altosid[○!R] 10F to the last instar larvae of C. yoshimatsui were 0.00065ppm and 0.0025ppm, respectively. As C. yoshimatsui larvae inhabit flowing water in drains, a test with short exposure to Altosid[○!R] 10F was undertaken. The IC_<50> value under 2hr exposure to Altosid[○!R] 10F was 0.0044ppm. The field test was conducted during autumn, 1980,against natural populations of C. yoshimatsui and Chironomus sp. in a Tokushima City drain. The concentration of Altosid[○!R] 10F was 0.59ppm of active ingredient/flowing water volume in the drain during treatment time. Then, after Altosid[○!R] 10F was diluted 200-fold with water, the solution was poured into the upper course of the drain for 15min. It was effective for a long period ; neither C. yoshimatsui nor Chironomus sp. emerged for more than 30 days.

View full abstract

Drift of invertebrates following the applications of temephos and fenitrothion was studied in a small stream. Drifting pattern was markedly different among species and between insecticides even in the same species. A large number of Anisogammarus annandalei drifted immediately after the passage of each insecticide, but Surber samples taken three days after the applications indicated the continuous presence of this species in both cases. Although Baetis sp., Nemouridae, Epeorus sp., Perla quadrata and Simulium sp. showed a similar drifting pattern each other in both insecticides, the beginning of the drift and the peak of the drift in these species were earlier for fenitrothion than for temephos. Dolophilodes sp. drifted lastly in the case of temephos and did not drift with fenitrothion. Arctopsyche sp. and Geothelphusa dehaanii were not affected by these insecticides.

View full abstract

Preliminary field study on larvicide formulations for onchocerciasis vector control in Guatemala was carried out in two rivers, Lavederos and Pajal, both located in San Vicente Pacaya, Department of Escuintla, in 1978. Temephos was more effective than fenitrothion against the larvae of Simulium ochraceum at the dose of 1ppm (AI) for 10min water discharge. Using temephos, no marked difference was observed in efficacy among the three formulations, namely 50% EC, 50% WDP and 10% solid. A solid formulation of temephos was considered to be the most convenient in field operation for its easiness in transportation, usage and safety in handling. Within two weeks after application, no mature larvae and pupa appeared in controlling area. A fortnightly application interval was selected, based on this result.

View full abstract

The effects of six organophosphorus insecticides (Fenitrothion, Dichlorvos, Diazinon, Propetamphos, Chlorpyriphosmethyl, Fenthion), one carbamate insecticide (Propoxur), one chlorinated insecticide (γ-BHC) and one pyrethroid insecticide (Permethrin) to a colony of Blatta lateralis were investigated by the topical application method. Dichlorvos and Permethrin were most effective; Fenitrothion, Diazinon, Propetamphos and Chlorpyriphosmethyl were moderately effective, and Propoxur, Fenthion and γ-BHC were less effective. When compared with the LD-50 values per insect of other two species of cockroaches, B. lateralis was more susceptible than Periplaneta fuliginosa but less susceptible than Blattella germanica. Males were more susceptible than females in respective species. On the basis of the effectiveness of the same body weight, B. lateralis was most susceptible to all the tested insecticides. The females of B. lateralis and B. germanica were less susceptible than males, while the effects of P. fuliginosa varied with insecticides.

View full abstract

Including the first two cases of human infestation with ixodid ticks that were reported by Ogura and Takada (1925) in Hokkaido, a total of 10 cases have been reported until the present time. The author adds the other 7 cases of human infestation with females of Ixodes persulcatus Schulze : case 1,left scapula; case 2,left inguen; case 3,lower part of right nipple on breast; case 4,lower part of right occipital region; case 5,parietal region; case 6,inside of left forearm; case 7,left side of waist. Tick species found from these 17 cases were 12 Ixodes persulcatus, 3 I. ovatus, 1 I. nipponensis (?), 1 I. ricinus (?). Of these 17 cases, 2 cases were found in late May, 7 cases in June, 3 cases in July, 1 case in August and 2 cases in September; 2 cases were unknown of their month of occurrence.

View full abstract

The larval habitats of tabanids were surveyed in the Noto Peninsula in 1979. In total tabanid larvae of 9 species were collected from 5 different habitats. The main breeding places of Tabanus trigeminus, T. takasagoensis, and T. kinoshitai were in paddy fields, while T. chrysurus mainly inhabited on mountain streams.

View full abstract