The 4th stage larvae (L₄s) of Gracilacus sp.² prior to lethsargus withstand unfavorable conditions for a longer time than lethargic L₄s and adults; for more than 42 months in soil kept in polythene bags and at least 80 days in water-saturated soil. For all thicknesses of cuticle, the ratio of the external cortical and basel layer of the quiescent L₄s was ca. 10% and 55%, respectively, being the largest in all stages examined. With the development of L₄s to adulthood, the permeability of cuticle increased. The intestinal cells of L₄s were filled with lipid droplets, which decreased in amount and some of which changed into the age pigment granules in adults. In the course of the formation of adult cuticle, electron dence balls appeared in the lateral hypodermis of the lethargic L₄s. Changes in survivability with development is discussed from an ultrastructural viewpoint.

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The compaound eyes of seven species of longicorn beetles were opbserved by electron microscope, and the relationship between the activity and the structure was considered. Changes ao organellas during light-dark adaptation were also observed on one of these species. Corneal nipples were found in Leptura. Two central retinula cells were surrounded by six peripheral cells. Each cell contributed to the rhabdom formation, but the two central cells apparently formed one rhabdomere. The configuration of the rhabdom and the orientation of its microbilli in the transverse plane were variable according to species and activity. In diurmally active species, especially in the group active under bright sunshine, peripheral rhabdomeres were small and separated from neighboring ones. However, in nocturnally active species, rhabdoms were large. The ratio of rhabdom to retinula cells in the transverse plane was higher than 48% in nocturnal and less than 31% in diurnal species. Both primary and secondary pigment cells contained pigment grains which varied in diameter according to speces but, as a whole, teh former larger grains than the latter. In Paraclytus, palisades appeared at the basel part of rhabdomic microvilli, and were especially conspicuous in central cells during dark adaptation. In the light-adapted state, however, they almost disappeared.

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The prey preference of the red fox on small rodents was studied by faecal analysis of foxes and a census of rodents in Hokkaido, Japan. The study area included the home ranges of two fox families which were dtermined by tracking in the snow. The number of foxes, a maximum of twelve and a minimum of three, varied depending on the season. It appeared that, from the census of small rodents, Clethrionomys rufocanus was dominat and mice of the genus Apodemus were also fairly abundant in teh study area. A total of 941 faecal sample of the foxes were analyzed and it was indicated that C. rufocanus constituted a very high percentage of the consumed rodents. Ivlev's index was calculated from the percentage of dry matter of each species in the feces and the biomass of each in the study area. It was suggested that the red foxes preferred C. rufocanus to genus Apodemus. The factors afecting prey preference were discussed on the basis of the relationships between the habitats of foxes and prey rodents.

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Hemocytic ractions in relation to larval development of the silkworm, Bombyx mori, were studied by injecting goose erythrocytes (GRBCs) into the hemocoel. Prior to this study, the changes in the total hemocyte counts (THCs) and available hemolymph volume (AHV) were studied using the larvae 3hr after moult in order to determine GRBC concentration and the volume injected at each instar. There was a gradual increase in THCs and AHV from the 1st to the 3rd instar, while THCs and AHV increased remarkably from the 4th to the 5th instar. The hemocytic reactions to GRBCs were readily observed 3 hr after injection, and the results showed that the ability to induce a primary respnse (cyto-adherence) increased during post-embryonic development. The hemocyte types involved in this cyto-adherence included plasmatocytes and granular cells. The latter, in particular, showed a high adherent ability. Since the number of granular cells was increasing with age, it seemed likely that an increase of hemocytic reactions to GRBCs was due to the increase of granular cells.

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In the transmission of rice waika virus (RWV) by the green rice leafhopper, Nephotettix cincticeps UHLER, transmission efficiency slightly decreased in old adults, but no difference in efficiency was demonstrated between sexes. Both acquisition and inoculation threshold periods were ca. 30 min. The rate of infective insects incresed as the acquisition feeding period was incresed up to 12hr. No definite latent periods in the leafhopper could be demonstrated. Nymphs lost their ingectivity after they molted. The leafhopper adults retained infectivity for a short period after the termination of acquisition feed. Infetivity decreased drastically with time, and the longest retention period was two days at 25°C. After losing infectivity, insects could become reinfective by fresh access to a diseased plant. From the various transmission characteristics, RWV is classified as a semipersistent leaffhopper-borne virus based on the definition by SYLVESTER (1969).

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The native chrysomelid beetle, Gastrophsa, is a possible agent for use in the biological control of dock, Rumex obtusifolius, which is a noxious grassland weed in Japan. Two dispersal tests were performed by releasing marked overwintered adults in grasslamd fields to assess their potential for biological control. The beetles dispersed an area with a radius of almost 50 m around the release point. The farthest destance at which a beetle was recoverd was 106 m from the release point. Based on this finding, two release points perhectare of overwintered adults would be sufficient for the establishment of a colony in virgin grassland or for increasing their numbers where there is a low population. Female adults dispersed to greater distances than the males. Beetles dispersed both by walking (crawling) and flying. Their flight was observed most often around noontime on warm, windless days.

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The metabolism of several indole compounds in the gut of the bug Lygus disponsi was investigated. Al the indole compounds were more or less metabolized in the gut. The metabolic patterns of IAA, indole-3-propionic acid and indole-3-butyric acid with -(CH₂)_n-COOH in the side chain were similar to one another. Also, the compounds with -CH₂- in the side chain (indole-3-ethanol, tryptamine, serotonine, gramine, indol-3acetonitrile and indole -3-acetaldehyde) were converted to several metabolites. The metabolites of indole-3-butyric acid had auxin activity. The metabolites that appeared in the excreta of the IAA-feeding bugs were probably the substances conjugated by attaching some molecules to hte side chain of indole nucleus. The significance of the auxin metabolism by the bug is also discussed.

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Laodelphax striatellus harbours intracellular yeastlike symbiotes in the fat body, transmitting them to the next generation through the female ovary. High temperature, 35°C, destroyed the yeastlike in the mycetocytes. Under the continuous high temperature no adults were obtained. The population of symbiotes in the 5th-instar nymphs, which were previously exposed to the high temperature for 3 days after hatching (heat treatment), was reduced; approximately one twentieth of that in the normal 5th-instar nymphs. These heat-treated insects showed poor growth in spite of sufficient sucking of rice plant juice. More than 70% of the heat-treated 5th-instar nymphs did not become adults and a number of them died. In some of them, the adult duticle was not only deposited in part. The high temperature also exerted an infuluence on fecundity of this species. The heat-treated insects seem to be useful for the further study to explore the role of the yeastlike symbiotes.

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When JHA (ZR-515) was applied to late lat instar larvae of Mamestra brassicae destined for pupal diapause, some of the resulting pupae failed to enter diapause. The roles of the brain and the prothoracic glands in these pupae continuing adult development were examined. Extirpation of teh brain within 10 hr after pupal ecdysis did not prevent adult development, but ablation of the prothoracic glands at the same stage disrupted metamorphosis. These result suggest that the brain does not play an important role in the prevention of pupal diapause by JHA application. Brains from JHA-treatd pupae which failed to enter the diapause had enough prothoracicotropic hormone (PTTH) activity to cause pupation of dauer larvae. Brains with no PTTH activity could not be activated by in vivo culture in the haemocoel of isolated pupal abdoments to which JHA was then applied. However, the pupal inactive brains did acquire PTTH activity when β-ecdysone was injected into the pupae. It is proposed, based on these results, that an increae in the PTTH activity of teh brain is elicited by ecdysone from prothoracic glands activited by JHA. It is concluded from these results that JHA applied to the last instar larvae are maintained even at the pupal stage and activates the pupal prothoracic glands to secrete ecdysone, which the ecdysone plays an important role to prevent to enter the pupal diapause. Furthemore, the ecdysone also activates the diapause pupal brain to secrete PTTH which in turn activites the prothoracic glands; probably this hormone secreted in this way takes part in the induction of diapause prevention.

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Biological studies of three spider mite species, Oligonychus ununguis (JACOBI), Panonychus citri (MCGREGOR) and Tetranychus urticae KOCH, were conducted under fairly constant temperature (25°C) and moisture (52% RH) conditions. The total developmental time was shorter in T.urticae than in the other two species, and the total fecundity and average egg production per day were significantly grater in T. urticae than in the other. The egg hatchability was generaly high in all the three species, while among these it was slightly lower in O. ununguis. Relatively high proportion of females, ca. 70 to 80 percent in P. citri and ca. 65 to 70 percent in T. urticae, was observed, but in O. ununguis it was ca. 50 to 55 percent. The intrinsic rate of natural increase (r_m), the net reproductive rate (R_o) and the mean generation time (T) were evaluated as follows : O. ununguis : r_m=0.178, R_o=24.72 and T=18.02. P.citri : r_m=0.162, R_o=24.36 and T=19.71. T. urticae : r_m=0.259, R_o=65.00 and T=16.16. It was concluded that T. urticae had significantly high reproductive petential, and postulated that this fact caused its high adaptability to its herbaceous host plants.

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Factors improving the attractivenness of traps baited with the synthetic sex attractant of Chilo suppressalis, i.e., appropriate mixture of Z-11-hexadecenal (HDAL) and Z-13-octadecenal (ODAL), were examined in teh field. Both rubber septa and polythylene capsules were good dispensers for loading of teh chemicals because they retained attractiveness for a long period. The amount of the attractant loaded on rubber dispensers was shown to be a critical factor. Attraction was shown by the dispensers loaded with 0.1-10mg of the attractant. Two mg was the best dispenser, having caught about 64% of the catch of virgin female traps. The ratio of the two pheromonal components was not so critical for attraction. Attractiveness was revealed by the mixutures rangeing in ratios from 20 : 1 to 1 : 1 (HDAL : ODAL). Among these, 3 : 1, 5 : 1 and 7 : 1 were more attractive than other mixtures.

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Two additional components of the female sex-attractant pheromone of the smaller tea tortrix moth, Adoxophyes sp., were isolated by a bioassay employing the release and trapping of male moths in a field cage. The two minor components isolated were identified as (E)-11-tetradecenyl acetate and 10-methyldodecyl acetate. Thus, the sex pheromone of this species is a four-component system comprising (Z)-9-, (Z)-11-, and (E)-11-tetradecenyl acetates and 10-methyldodecyl acetate in a ratio of 63 : 31 : 4 : 2. Besides the four pheromone components, seven acetates were identified as pheromone analogues. These are dodencyl, dodeceyl, tidecenyl, tetradecyl, 12-methyltetradecyl, pentadecenyl, and hexadecenyl acetates. A synthetic mixture of teh four pheromone components was competitive with live virgin females in the field with respect to attractiveness for males.

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The presence of Bombykol, 10-trans, 12-cis-hexadecadien-1-ol in female Bombyx mandarina Moore was demonstrated by comparing the pheromonal activity, UV-absorption and gas liquid chromatogram of crude female extracts with that of B. mori and with authentic Bombykol. The purified active compound (12 μg) was isolated from 399 females of B. mandarina, whose mass spectrum and chromatographic behaviours were completely identical with those of authentic Bombykol.

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