The effect of insecticide application on the density of larvae of the rice stem borer and spiders was studied from 1970 to 1973 in Akita. Below an economic injury level which corresponds to about one injured stem per hill, the density of the old larvae and pupae of the rice stem borer in the 1st generation was about equal between the plots applied with an insecticide and ones not applied. From these facts, the high emergence of the 2nd generation was not expected even when an insecticide was not applied in the 1st generation below the economic injury level. The density of the old larvae in the 2nd generation was high in the plots below the economic injury level. Therefore, it was impossible to dispense with insecticide application even when the injury by the 2nd generation was below the economic level if the emergence of next year's 1st generation was apprehensive. When insecticides were applied at ordinary concentration to the 2nd generation, they affected the density of spiders which seemed to be the important natural enemies of hoppers. The effects of BHC, EPN, PMP and MEP on spiders were large, but those of Cartap and chlorophenamidine were comparatively small. The application of 50-100ppm chlorophena-midine, that was 1/5-1/10 of an ordinary concentration, indicated satisfactory control of rice stem borer with little effect on the density of spiders.

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The fine structure of the cytoplasmic-polyhedrosis virus (CPV) of the silkworm was studied with special reference to the spherical particle (SP) attaching to the top of projections of the virions. The SPs were observed in both liberated and free CPV which were purified with a cushion of 50% sucrose from freshly prepared samples. These SPs were homogeneous in size and shape, and attached only to the top of projections but not to the other parts of the CPV. The size of SP was about 12nm in diameter. After treatment of CPV with fluorocarbon (50%), ether (50%), DOC (0.5%) or trypsin (0.5mg/ml), SPs could not be detached from the top of projections. Some copolymer-like structures of SP (or SP-like particle) were also observed. Their overall size were about 60-70nm, apparently smaller than that of CPV (about 100-110nm). They appeared to be a subunit structure as hexamer or higher co-polymer, consisting of SPs, projection-like structures and large spherical particles. Sometimes, such polymer existed on the top of projections of CPV. Nothing has been known about the nature and role of these polymer for the CPV infection in the silkworm.

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During the adult and a part of pupal stages, the dorsal vessel in insects pulsated in three phases; the rapid, the rest, and the slow phase according to its difference in pulse-frequency. In the rapid phase the pulse wave moved toward anterior along the dorsal vessel, normal pulsation, while in the slow phase toward posterior, reverse pulsation. The point of automatism, at which the pulse wave occurred, transferred after the rest phase. The transfer of the point occurred also after a lack of one pulse or a conflicting pulsation, and stopped temporarily after a fluttering or a movement of the body. The pulse wave recorded as a cardiogram showed the expanding or the contracting movement of the dorsal vessel. During the normal pulsation a rapid contraction was followed by a slow expansion, while during the reverse pulsation a rapid contraction returning back to the initial dimension occurred after an expansion in a wider degree.

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Diapause in Oligonychus ununguis (JACOBI) at Hiratsuka, Kanagawa Prefecture, was broken by chilling the eggs at 10°C for 75-100 days, at 15°C for 100-120 days, at 4.5°C for about 120 days, or at 0°C for over 120 days. Winter eggs of this mite were collected from a chestnut orchard of the Fruit Tree Research Station at 15- or 30-day intervals from early November to mid-March and incubated at 25°C. It was found that most winter eggs failed to hatch before January, but their hatchability increased in the later season and reached the maximum between late February and early March. From these results, it was assumed that diapause in O. ununguis is terminated by early March. The relation between temperature and velocity of development of the eggs was linear between 15 and 27°C after the termination of diapause. Based on this relation, the threshold of development was estimated at 5.6°C and the total effective temperature for development from the termination of diapause to hatch was 270.3 degree-days. The hatching time of the winter eggs, predicted by the sum of effective temperature above 5.6°C from March 1 at Hiratsuka, coincided well with the observed dates of 50% egg hatch, April 27 in 1969 and May 2 in 1970.

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The maturation process of the granulosis virus in fat-body cells of Plutella xylostella was observed electron-microscopically and the maturation sequence of the virus was suggested as follows: (1) appearance of nucleocapsids associated with the endoplasmic reticulum; (2) regular stacking array of nucleocapsids; (3) random release of nucleocapsid from the cluster to the cytoplasmic matrix; (4) envelopment of nucleocapsid with a membrane which originated from de novo membrane morphogenesis in the cytoplasmic matrix; (5) encapsulation; and (6) completion of inclusion body formation. The enveloped nucleocapsid was distinguishable morphologically: the anterior part had no structural characteristics, but the posterior part had a spicular structure at the end of envelope. Initial deposition of inclusion body protein always started at the anterior part of the enveloped nucleocapsid, and encapsulation was never seen at both ends of the enveloped nucleocapsid. At an advanced stage of the infection, some characteristic structures were observed in the host cells. Homogeneous fine granules appeared inside of the curved endoplasmic reticulum. Ring-shaped structures also appeared associated with the endoplasmic reticulum. However, these structures disappeared with degeneration of the endoplasmic reticulum. Compact clumps of material appeared in the area of sequestration of cell organellae. The figure of this compact mass was quite similar to the “virogenic stroma” which had been reported in other granulosis.

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Movement behavior of the final instar larvae of M. brassicae and S. litura from a food plant to another was experimentally investigated. In both solitary and crowded (5 or 10 larvae) conditions, M. brassicae larvae hardly emigrated from a leaf of Chinese cabbage or Chinese mustard, but tended to emigrate from that of sweet potato. On the other hand, S. litura larvae scarcely emigrated from any leaves when tested under the solitary condition. The order of feeding preference of M. brassicae larvae was Chinese cabbage>Chinese mustard>sweet potato, and that of S. litura larvae was sweet potato≈Chinese mustard>Chinese cabbage. Thus the emigration of M. brassicae larvae seems to occur depending less on the larval density during the experiment, more on difference of the species of food plant. However, the emigration of S. litura larvae may be more dependent on the larval density during the experiment. When a larva of one species was mixed with four or nine of the other, the former scarcely emigrated. This suggests the existence of some species-specificity in both the density-dependent stimulation and the larval susceptibility to such stimulation. When 20 larvae were released on a central plant of 25 Chinese mustard plants in a mimic field (in a wooden pallet, 1m×1m), M. brassicae larvae showed concentric consumption on the central several plants, but S. litura larvae showed a dispersed infestation almost all over the plants after a few days.

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The fauna of predaceous insects was studied at 37 citrus orchards in various parts of Japan including Amami-Oshima, Shimabara, Omura, Yamaguchi-Oshima, Ehime and Arita. Among 16 species of the predaceous insects, Cybocephalus gibbulus, Saula japonica, Pseudoscymnus hareja, Scymnus hilaris and Stethorus japonicus are important predators of citrus pests. C_λ-index (MORISHITA, 1959) indicated a complete dissimilarity of the fauna of predaceous insects between Amami-Oshima and other parts, and a tendency of the reduced similarity among various parts other than Amami-Oshima as the latitude differed. The predators' density had a tendency to rise with the increase of pests' density. The higher density of predators was revealed at the orchards where no pesticide had ever been applied than at those applied. Locality difference of the spider fauna could not be found clearly because of the shortage of collected material, nevertheless the result suggested some difference.

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From the rearing experiment of A.l. corvina on the leaves of lettuce under different temperature conditions from 10 to 32°C, it was estimated that the developmental zero point for the larva and pupa was 6.5°C and 8.5°C, respectively. The effective day-degree required for the development from the first instar larva to pupa was also estimated to be 840. According to the light-trap record, the moth capture was shown by a curve with two peaks in spring and autumn, suggesting biannual occurrence. However, this suggestion was wrong since it had been revealed that the adult aestivated in summer. In the early summer, the adults assembled to the particular aestivation sites, hid under panels of a building or in crevices of walls, and stayed there for 30-50 days. After awakening from aestivation, they moved away from the place for oviposition in the middle of autumn. Such aestivation sites were found not only in mountainous place but also in plain region of Mie Prefecture. The aestivation of adult was terminated when they were kept at 20°C with 11-hr lightening. The peak times of the moth capture coincided with the seasons when they assembled to and departed from the aestivation sites. Therefore, it is concluded that this insect occurs only once a year.

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The relation between the ovarial development and the copulation was examined with the green rice leafhopper, Nephotettix cincticeps (Jassidae), the brown planthopper, Nilaparvata lugens, the white back planthopper, Sogatella furcifera, and the small brown planthopper, Laodelphax striatellus (Delphacidae) by vivisecting the insects reared in a laboratory. The ovarial development in the three species of delphacids progressed more rapidly than in N. cincticeps, that is, the earliest females having full grown eggs appeared on the 3rd day of emergence in the delphacids, while on the 6th or 7th day in N. cincticeps, at the same temperature of 25°C. However, the speed of ovarial development varied widely even in the same species and more than 20 percent of females examined possessed undeveloped ovaries even at the 15th day of emergence in N. cincticeps and at the 10th day of emergence in N. lugens and L. striatellus. In the delphacides, copulation began on the second to the 3rd day of emergence and most females completed copulation by the 4th or 5th day of emergence, though more than 10 percent of females remained uncopulated throughout the observation period of 8 to 10 days. On the contrary, the copulation of N. cincticeps began on the 4th day of emergence and all the females copulated by the 9th day of emergence. Many females of N. cincticeps copulated successfully before the ovarial maturation, while in the delphacid females having no full grown eggs seldom copulated successfully. Thus, N. cincticeps differed from the three species of delphacids in the time of copulation in relation to the ovarial development.

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Two pairs of newly emerging Cadra cautella females and males were confined in a glass pot (11-cm diameter, 7-cm height) with a pheromone holder impregnated with 100μg of cis-9, trans-12-tetradecadien-1-ol acetate (c-9, t-12-TDDA), the synthetic sex pheromone of C. cautella. The oviposition into the pheromone-treated pot was delayed for ca. 2.8 days from that into the untreated pot, and the total number of eggs laid in the treated pot was decreased, though this difference was not significant. However, the oviposition of more than 5 pairs in a pot was not delayed with 100μg of c-9, t-12-TDDA. When 2 pairs of C. cautella were confined in a pot with the different amounts of c-9, t-12-TDDA (12.5, 25, 50, 100 and 200μg respectively), the number of laid eggs was significantly decreased from that in the untreated pot for the first 3 days, except the case of 12.5μg. However, there were no significant differences among the total numbers of oviposited eggs, though their decreasing tendency was apparent. Therefore, the mating of C. cautella was disturbed more or less even in a limited space such as the glass pot with the synthetic sex pheromone. The reason why the mating disturbance was not attained to 100% was possibly ascribed to the population density in the pot. The synthetic sex pheromone may have no effect on the eggs laid by the mated females, because of normal adults emerging from them.

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cis-9-Tetradecenyl acetate (cis-9-TDA) and cis-11-tetradecenyl acetate (cis-11-TDA), components of the sex pheromone of the smaller tea tortrix moth (Adoxophyes fasciata Walsingham), showed the potent inhibitory effect on mating of the tortricid moth under the laboratory conditions, when the compounds were presented individually or in combination. Aereal concentrations of cis-9-TDA, cis-11-TDA, and a mixture of the two (cis-9:cis-11=7:3) for more than 90% inhibition of mating were 3, 0.3, and 3μg/l, respectively. trans-Isomers of 9- and 11-TDA were far less active than the cis-isomers as mating inhibitors. Distribution of the sex pheromone or the individual components in the field strongly inhibited the orientation behavior of male moths to a virgin female-trap (VF-trap). However, cis-11-TDA, the best mating inhibitor under the laboratory conditions, showed only weak repressive effect on the attractive power of a VF-trap in the field, when the compound was attached to the VF-trap. cis-9-TDA was more potent than cis-11-TDA, and the trans-isomers were more active than the cis-isomers, as a represser of male attraction in VF-traps.

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To determine the feasibility of using radiation for the disinfestation of timbers, the radiosensitivity of three species of ambrosia beetles, Xylosandrus germanus, Xylosandrus compactus and Xyleborus semiopacus was studied. Lethal doses on the female adults determined on 12 days after gamma irradiation showed the LD₅₀ and LD₉₉ to be 39krad and 73krad for Xylosandrus compactus, 50krad and 91krad for Xylosandrus germanus and 94krad and 130krad for Xyleborus semiopacus. Doses required for inhibition of adult emergence of three species were 3krad for the 5-day-old eggs, 5-7krad for the 3rd-instar larvae and more than 10krad for the pupae. The sterilizing dose was 2-4krad for all developmental stages of three species. When the female adults mated soon after emergence were exposed to 2-4krad, Xylosandrus germanus and Xylosandrus compactus were found to produce only males in the next generation. The ambrosia beetles were sterilized with considerably lower doses than the bark beetle, Cryphalus fulvus was. Boring capacity as well as F₁-adult emergence appeared to be effectively inhibited when adults and pupae of the ambrosia beetles were irradiated with 10-30krad.

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When a definite amount of the filtrate obtained from the haemolymph of an infected larva of the silkworm or from the culture of Spicaria prasina (MAUBLANC) SAWADA was injected into the 3rd- or 4th-instar larvae of the silkworm belonging to the four-molter hybrid, many larvae became precocious pupae without larval molting. The ratio of precocious pupae was higher when the filtrate was injected to the younger larvae than the older. On the contrary, either pupation from the 5th-instar larva or emergence from the pupa was inhibited by the injection of filtrate of the fungus culture. The active substance in the culture filtrate was extracted from water layer with organic solvents, such as ether, chloroform, petroleum ether, and n-butanol. While, the substance could not be extracted with methanol, ethanol, and ethylacetate, and was precipitated with acetone. The substance was inactivated by heating at 50°C for 10min, even though no activity was lost following the treatment with buffer solution at pH 1.7 or 9.7 at about 23°C for 1hr.

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The leaves of 117 plant species were extracted with methanol. After evaporation of the solvent, each aqueous residue was separated into chloroform-soluble and water-soluble fractions. The chloroform-soluble fraction was added to an artificial diet which was composed of mulberry leaf powder (50%), defatted soybean powder (24%), cellulose powder (15%), citric acid (4%), agar (5%), L-ascorbic acid (1.5%), sorbic acid (0.5%) and distilled water (2.5ml/g solid). To the diet, after evaporation of the chloroform, was added the water-soluble fraction. The diet thus prepared was fed to the 4th-instar larvae of the silkworm, Bombyx mori L., which were grown at 25°C for 6 days.
Plants tested were classified into the following five groups according to their effects on the growth of larvae. Group 1: all of the larvae died during the test period. Groups II, III and IV: strong, moderate and weak retardation of the larval growth were observed in the order of numerals. Group V: no significant effects were observed. Thirty-four species of plants were assigned to group I, and 16 to II, 19 to III, 22 to IV and 26 to V, respectively. Plants belonging to Rutaceae, Ericaceae, Taxodiaceae, Magnoliaceae and Araliaceae were found to be the most effective. The methanol extracts of 25 species showing marked efficacy were fractionated into ethyl acetate-soluble acidic, neutral and basic fractions, and ethyl acetate-insoluble aqueous fractions. The biological activities were mainly observed in the neutral fraction.

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