The following ability of Marietta carnesi, a secondary parasitoid of diaspine scales, was suggested for host discrimination by investigation of materials collected from natural fields and laboratory experiments. The female of Marietta carnesi was able to distinguish between healthy Chrysomphalus bifasciculatus and those already parasitized by primary parasitoids, and selected the latter for oviposition. It was also capable of distinguishing between various developmental stages of the primary parasitoid, Comperiella bifasciata, developing within the secondary hosts, and selected scales containing pupae of the primary parasitoid for oviposition. Sometimes, however, it also deposited eggs on scales containing larvae of the primary parasitoid when densities of pupae of the primary parasitoid were decreased. Ovipositing females of Marietta were also able to distinguish between healthy pupae of Comperiella and its own species, avoiding autoparasitism. Finally, Marietta discriminated healthy pupae of Comperiella and those already parasitized by its own species, and avoided superparasitism. Nevertheless, superparasitism sometimes occurred when the densities of Comperiella were decreased.

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Linear multiple regression models to predict the population of summer and autumn generations of the arrowhead scale, one of the important citrus tree insect pests in Japan, were constructed. The population density at each specified developmental stage of the insect, average temperature, precipitation in each month of observation, etc. were used as variables in these analyses. These data were accumulated from 1960 to 1972 at experiment stations in Kanagawa, Shizuoka, Hiroshima and Kumamoto. The following two types of model were built up by statistically and/or biologically significant variables. ‘Type 1’: 4 separate models constructed for respective locations by using data obtained at each of the experiment stations noted above. ‘Type 2’: A common model constructed by using all data from the 4 experiment stations. In these five cases, the multiple correlation coefficients of the regression attained at least 0.8. These five models were used to predict the arrowhead scale population density in the two years following the observations used in the analysis, i.e., 1973 and 1974. The results show that the Type 2 model had high predictability but the Type 1 models did not have high predictability. This is because the Type 2 model was constructed by using data covering various different environments. Although the Type 1 models fitted thier own specific situations well, they were not sufficient to forecast future conditions because these models did not incorporate diverse experiences which might occur in the future. Hence, it is concluded that a multiple regression type model can have very high predictability, if it is built by using data obtained in various locations and many seasons, as was the Type 2 model in this study.

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The development and life history of the satyrid butterfly, Mycalesis gotama fulginia, which is an endemic insect pest of the rice plant, were studied in the laboratory, and life tables were developed in the paddies in 1976 and 1977 in Kochi and Aichi. The thermal threshold and thermal constant were 10.3°C and 777 day degrees, respectively. The diapause was induced in the 4th instar larva under short-day conditions of less than 13hr day-length. The growing stage of host plants significantly influenced the development of the larvae. The life tables showed that the mortality rate from egg stage to emergence of adults was quite low, i.e. 81.4%, when the eggs were laid on the young rice plants, but higher, i.e. 96.4%, in the ear forming stage. In the latter case, over 70% of the individuals died before the 2nd instar due to the failure of settlement of the hatchlings on the leaves. Natural enemies were not particularly effective. The satyrid butterfly has three generations in a year and the female adult can lay about 130 eggs on rice plants or gramineous grasses. The survival rates in paddies are high. Thus, the potential growth rate of the population on rice plants seems to be high. Nevertheless, the insect remains a minor pest of rice plant. The reason for this has not yet been determined.

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The seasonal fluctuation of pheromone trap catches indicated the fact that the oriental fruit moth repeats five generations a year in Okayama Prefecture. But twig injuries by fifth generation larvae were negligible in the peach field. The observational development zero and total effective temperature were calculated as 11.1°C and 383.7 degree-days from the number of days and average temperature interval between peak of emergences by the pheromone trap records. The second and subsequent emergence peaks coincided with that forecast time by the observational degree-days and accumulative effective temperatures. The result obtained in various districts indicated that the peak of primary generation was correlated with the temperatures during September through March and also with the annual average temperatures. The second and subsequent peak generation times at the seasonal prevalence in various districts coincided with that estimated time by the observational degree-days. The number of generations assessed with pheromon traps coincided with that estimated by dividing the cumulative effective temperature from April to September by the observational total effective temperature; a high correlation with the annual average temperatures was also demonstrated.

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In order to establish simple and rapid testing methods for antibiosis of the rice plant to the green rice leafhopper, three testing methods, germinated seedling, young seedling and leaf blade method were studied. A germinated seedling in a test tube was used for the first method. A young seedling in a plastic cylinder was used for the second method. A cut leaf blade in a test tube was used for the third method. The survival ratio of the nymphs fed on test plants was examined in these tests. Although it fluctuated largely, it was shown that resistant varieties can be distinguished from susceptible varieties. Both testing methods using the seedlings seemed to be suitable for the screenig of resistant varieties in any season, but unsuitable for the selection of crossing progeny because it was difficult to use the rice seedling for supplementary examination or breeding after testing. The leaf blade testing method could be used for various tests with attention to the survival ratio fluctuation, namely, screening of varieties, selection of crossing progeny. Consideration of the merits and demerits of each method is necessary for effective testing.

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The mature larvae of Echinocnemus squameus could not pupate and mortality increased with the lapse of time under flooding conditions. However, larvae transferred to the drainage condition pupated one week after the transfer. The critical soil condition related to pupation was about 80% water content, which corresponds to pF 0.8. When the water content of the soil was reduced, pupation was accelerated. There are six paired dosal hooks on the lateral side of the larvae. The spiracles were changed into these dosal hooks. Under flooding conditions, the larvae gathered around the rice roots and pressed the dosal hooks on them. They died within one or two days without the roots. These results suggested that the larvae obtained oxygen from the roots. When the soil was drained, the larvae parted from the roots and utilized gaseous oxygen in the soil. In the paddy, the emergence time of adults was affected by the time of drainage and the amount of rainfall. The early drainage accelerated pupation and hastened the emergence of adults. The injury of the hullcracked rice in the latter part of the ripening stage was caused by the adults of this insect.

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Adults and nymphs of Eurydema rugosum MOTSCHULSKY were reared on dried rape seeds and water. Dried rape seeds adhered to a gummed tape which was then hung within a container. Water was supplied to the bugs from the tip of a filter paper which was dipped into water. The containers were kept under conditions of 25°C and 16 to 17hr illumination. A container 8.4cm in diameter and 11cm high contained 10 pairs of the adults which laid about 200 eggs every 5-7 days. Eggs were deposited on the surface of the piece of paper placed inside the container wall and on jute strings hung beside the gummed tape with the rape seeds. The eggs hatched in 6.5 days and the nymphs grew to be adults in about 30 days, with a survival rate of about 92%. In the container, the piece of gummed tape of 115cm² fixed with rape seeds was able to supply food for about 300 nymphs throughout the whole nymphal period.

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In addition to practical applications in the control of rice blast disease, isoprothiolane (Di-isopropyl 1, 3-dithiolane-2-ylidene-malonate) is effective in reducing the population density of rice planthoppers, Nilaparvata lugens and Sogata furcifera, in paddies by submerged application for about one month at 360-400g of active ingredient per 10a. The experiments showed that isoprothiolane killed early instar larvae 6-10 days after the rearing on food plant containing the compound. Other effects, such as shortening of longevity and suppression of oviposition were also observed in adults of Nilaparvata lugens that had been reared since the 3rd instar on food plant containing isoprothiolane. The suppression of population growth of planthoppers in the field seems to depend on the multiplication of these effects caused by isoprothiolane.

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Ovicidal activity of cycloprate (ZARDEX^(R), ZR-0856, hexadecyl cyclopropanecarboxylate) against the Kanzawa spider mite, Tetranychus kanzawai KISHIDA, was investigated in relation to the age of eggs and compared with that of chlordimeform and tricyclohexyltin hydroxide. The effectiveness of cycloprate for malathion- and dicofol-resistant strains was evaluated. The selection by cycloprate was also made for 7 generations. Cycloprate inhibited the hatching and lethally affected the hatched larvae. The ovicidal activities decreased with the elapsed time of egg stage, in contrast with the activities of both chlordimeform or tricyclohexyltin hydroxide. Cycloptrate was effective on both malathion- and dicofol-resistant strains as well as susceptible ones. The egg susceptibility decreased by about 1/5 in both the 1st and 2nd selection, but it became almost constant after the 3rd selection.

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An egg-seeding method shown in Fig. 1. has been established. Under this method the eggs can be dispensed within 20 minutes on the media for producing one million mature larvae. This method may be further developed into a fully automatic method provided some improved dispensing nozzle is used and handling of trays of larval media is mechanized.

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