Insecticide susceptibility in two colour forms of the green peach aphid, Myzus persicae (SULZER), was evaluated using the potato leaflet dipping method. Susceptibility to acephate (Ortran) was higher in the green-yellow form than in the red form: the average LC₅₀ with 95% confidence limits was 25.7±10.6 ppm (5.768.1 ppm) in 13 clones of the green-yellow form and 79.4±21.2 ppm (22.3-273.5 ppm) in 12 clones of the red form of the aphid collected from potato fields. In the field investigation, the rate of the red form to whole green peach aphids caught by yellow pan water traps was over 30 % throughout the potato cropping period. The results indicate that insecticide susceptibi-lity of the green peach aphid should be tested in each colour form.

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Bacteriological and serological characteristics of the two Chinese strains of Bacillus thuringiensis, B. thuringiensis subsp. ostriniae and subsp. wuhanensis, were investigated. By serological test using 8b H factor serum, it was shown that all isolates of B. thuringiensis serotype 8 obtained from the sericultural farms in Japan belonged to subsp. morrisoni (serotype 8a:8b). Saturation test of subsp. ostriniae H antiserum with subsp. morrisoni revealed that the H antigenic structure of subsp. ostriniae was 8a:8c. O agglutination tests indicated that subsp. ostriniae shared common O antigen(s) with the reference strains of subsp. finitimus, subsp. alesti, subsp. aizawai, subsp. morrisoni, subsp. tolworthi, and subsp. darmstadiensis. It also appeared that subsp. wuhanensis belonged to kurstaki-galleriae-aizawai group with respect to the O antigenic structure. The parasporal inclusions produced by subsp. ostriniae showed no toxicity to the silkworm larvae, Bombyx mori.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Oviposition, development and sex ratio of the Oriental fruit fly, Dacus dorsalis HENDEL, were investigated, and changes of punctures by oviposition on the plum fruit, Prunus salicina LINDL, were observed in relation to the degree of maturity of the host fruits. The females laid their eggs on the plum fruit irrespective of the degree of maturity. It took 140 seconds on average to complete one ovipositing action, during which 5 eggs were laid on average. The number of eggs laid per ovipositing action increased as the times required for the action became longer. The newly-hatched larvae developed more rapidly and the total developmental period from egg to pupa was shorter when they inhabited the fruits in more advanced stage. There was no significant difference between sexes in the total developmental period on every fruit investigated.Survival rates from egg to adult emergence were about 30% on uncoloured fruits and 50% on coloured ones. Sex ratio was always about 1:1. In the course of time, the punctures by oviposition turned coloured, dented slightly and expanded like steeped oil on every injured fruit observed. The punctures of oviposition were easily distinguished from those marked with an insect pin, as the pin-point punctures did not exhibit further changes.

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[in Japanese]

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Torymus (Syntomaspis) sp. has been said to be the most effective species among indigenous natural enemies of the chestnut gail wasp, Dryocosmus kuriphilus YASUMATSU because the former has a synchronous life cycle with the latter. The present study aimed to clarify how the oviposition period of the parasitoid synchronizes with the vulnerable gall stage of the host cynipid. Field censuses were made at three stations in Fukuoka city and its suburbs in the spring of 1978. The female parasitoids emerged in the latter half of March from the withered galls formed in the previous year, and oviposited in the cells of newly growing galls in which the matured cynipid larvae inhabited in the first half of April. Emergence and oviposition occurred simultaneously at these three stations. On the contrary, the vulnerable times of galls were different among the stations and trees. Thus, the parasitoid synchronizes with the host in many cases, but do not in a particular tree. It was suggested that the effectiveness of this parasitoid as a biological control. agent should be evaluated with the consideration of heterogeneity of gall development on each tree.

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The toxicity of 15 fungicides which are common to the control of citrus diseases upon the predacious mite, Amblyseius deleoni MUMA et DENMARK, was evaluated to determine the selective fungicides least toxic to the predacious mite in the integrated chemical and biological control programs. The tests were carried out on direct toxicity and residual toxicity for adult females in the laboratory at 25°C and 80-90% R. H. The toxicity was assessed by the mortality, the fecundity and the developmental rate of eggs laid during the test periods. A. deleoni exhibited tolerance to 6 compounds including Difolatan, streptmycin, Daconil (tetrachloroisophtalonitrile), dithianon, oxine copper (copper 8-quinorate) and Kocide (copper hydroxide + CaCO3 0.5%). Maneb, mancozeb and propineb were highly toxic. Zineb, colloidal sulfur and be' nomyl were low toxic to the adult females, but highly toxic to the immature stage for a long time. Depression of mite fecundity was caused by benomyl, thiophanatemethyl and thiophanate. The influence of Bordeaux mixture was observed only in the case of direct application.

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In order to determine the relation between the dispersal of Pteromalus puparum (L. ), a pupal parasitoid of Papilio xuthus L., and percentage parasitism by it, releases of the parasitoid were made four times within an area covering a space of 18m by 50m and containing four citrus groves where hosts were placed artificially. After the releases, parasitism percentage markedly increased in the groves where the releases were made, but it was negligible in the other non-released groves. Observations of the released parasitoids on and near the hosts were made two or three times a day for 8 days after one of the releases. From the results of the observations, it is suggested that a large portion of the released parasitoids emigrated from the area soon after the release, but that the rest stayed for more than a week.

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Changes in the foraging activity of P. chinensis antennalis PEREZ in relation to its colony development were investigated. under field conditions. Changes in the numbers of cells, 3rd to 5th instar larvae and workers in relation to the colony development were also investigated. When the numbers of cells and 3rd to 5th instar larvae were small before the emergence of workers, both hunting activity and foraging activity for liquid food were low. After the first worker emerged, hunting activity increased with a rapid increase in the numbers of cells, 3rd to 5th instar larvae and workers. When 3rd to 5th instar larvae and workers became numerous, the hunting activity reached a maximum. Thus, the hunting activity was high during late June to early August. The foraging activity for liquid food, however, was lower than the hunting activity in this period. Once the first male emerged, cell development ceased and the number of 3rd to 5th instar larvae decreased rapidly. Workers in this postmale substage expended more labor for collection of liquid food than for hunting. It is suggested that some colony factors such as the numbers of 3rd to 5th instar larvae and workers in a nest strongly affect the hunting activity.

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