The oviposition site on orchardgrass of the armyworm, Pseudaletia separata WALKER, changed with the regrowth of grass after harvest. A lager number of eggs was laid on dead leaves than on living leaves on the day after harvest and about 40 days latter, but the situation was reversed about 20 days after harvest when the grass was regrowing rapidly. The greater part of the eggs was laid within the folds of unexpanded living leaves and dead leaves. After living leaves expanded, 21.9-88.3% of the eggs laid on them became exposed. No eggs on dead leaves were exposed until egg hatching. When eggs laid on dead leaves were placed on the ground in the grassland, the exposed eggs suffered a heavy mortality, while the eggs concealed within folded leaves were more viable due to protection. The mortality of the eggs which were attached to leaves at different heights above ground decreased in the order of 0, 15, 30cm. Among the egg predators concerned, an ant, Pheidole fervida SMITH, predominated over others in all the seasons tested. These results suggest that the oviposition preference of crevices by the female armyworm moths may play a role in their escaping from the attack of egg predators, especially when they laid eggs within folds of dead leaves.

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At a constant temperature of 20°C bugs reared under short-day photoperiod (SD) (12L-12D) regime from the first instar nymphs entered the diapause and exhibited the coloration change from green to brown in the adult stage. Transfer of adults from long-day photoperiod (LD) (15L-9D) to SD regime suppressed oviposition and induced the brownish coloration. After transfer from SD to LD regime adults started laying eggs and their coloration became green. In addition, the females which received for a longer period under SD regime tended to oviposit earlier after transfer. These results indicate that P. stali is sensitive to photoperiod even after adult emergence and that the diapause development proceeds under SD regime without the exposure to a low temperature.

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Life history parameters of the grape (Vitis vinifera L.)-adapted Tetranychus kanazawai population (Gp) and the bean (Phaseolus vulgaris L.)-adapted one (Bp) were investigated on grape and bean, and were compared between populations or host species. On grape leaf, as Gp showed a higher survival rate of immature stages, developed more quickly and showed a higher oviposition rate than Bp, the value of r_m was greater for Gp than for Bp. On bean leaf, however, these differences between the two populations were not observed. The r_m values of both populations were much greater on bean leaf than on grape leaf.

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Feeding behavior of the adult armyworm was observed in two field cages (2×2×2) with and without the supply of a brown sugar solution as food, and in a cage kept at of the constant room temperature of 21.5±1.5°C with the supply of a sugar solution as food. Only a very small number of adults was attracted to the food on the 1st day after emergence. Active feeding started on the 2nd day and reached a peak on the 3rd or the 4th day. The daily feeding peaks which occurred just after sunset (or light-off) and again before sunrise (or light-on) from the 2nd day to the 5th day, were less distinct on the 7th day on account of a rather continuous activity. The adults, which did not receive the sugar solution, took the honeydew from aphids on corn plants, mated and oviposited normally, though they showed a slightly lower percentage of mating than those fed on the sugar solution. Daily intake of sucrose solution per adult female and its effect on oviposition were investigated in 900ml glass cups, with the supply of 0.1, 1, 3, 5, 10 and 30% sucross solutions. The peak feeding occurred earlier, and the total amount of sucrose absorbed per female increased linearly, with increasing concentration of the sucrose solution. The number of eggs laid per female increased with the sucrose intake within the 0.1-10% range, and decreased at a concentration of 30%. Starvation of adult females decreased fecundity, but not egg hatchability.

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Aphids at the late larval stages were collected from laboratory colonies that had been reared on Veronica persica. The larvae were placed in petri dishes, and every hour, they were observed and the number of winged adults was counted in the laboratory. Aphids showed the same molting behavior both in the daytime and at night. Newly formed winged aphids were transferred on cut papers inside a test cup and every hour of the take-off behavior was observed. Aphids took off mainly after 10-24h, though the range of the period preceding flying ranged from 1 to 31h. Many young adults took off from 7:00 (around sunrise) to 14:00. This observation was accounted for the findings because aphids that molted from the day time to the night took off concentrically in the next day. Newly formed winged aphids were transferred on fresh host plants inside a test cup and every hour the plants were observed and the number of individuals which took off was counted. Time of take-off in the aphids was delayed composed with the condition in which host plant were absent: a few newly molted adults took off on the day of emergence, which most aphids took off on the next day, and the number of individuals which took off gradually decreased thereafter. None of the molted adults produced offsprings on the same day, 40% of the adults produced offsprings on the next day and the ratio and number of offsprings per adult increased with time.

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From the stand point of quality control, experiments were conducted to compare several reproductive characters in wild and mass-reared melon flies, Dacus cucurbitae COQUILLETT. The mass-reared strain used in these experiments was obtained from the mass-rearing culture maintained on artificial diet at the mass-production facility of Okinawa Prefectural Fruit Flies Eradication Project Office. This culture had been reared through about 20 generations from initial laboratory colonization. Individuals of the wild strain were obtained as larvae from infested fruits in fields. The characters compared in these experiments included the pre-oviposition period, total number of eggs oviposited per female flies throughout the lifespan, frequency of oviposition, rate of oviposition (number of flies which oviposited/time when the artificial egging device was set), post-reproductive period, frequency of mating and longevity in male and female flies. The pre-oviposition period, post-reproductive period and longevity in the male and female flies of the mass-reared strain were shorter than those of the wild one. The total number of eggs oviposited throughout the lifespan and the rate of oviposition of the mass-reared strain were higher than those of the wild one. Frequency of oviposition and mating for the mass-reared strain were higher than those for the wild one. The coefficient of variation of the pre-oviposition period, total number of eggs oviposited per female throughout the lifespan, rate of oviposition, post-reproductive period and frequency of mating for the wild strain were higher than those for the mass-reared one. But the coefficient of variation of the pre-mating period, longevity in males and females for both strains showed approximately similar values. It was concluded that the mass-reared strain shows a shorter maturation period, higher fertility, shorter longevity and lower variation in reproductive characters when compared with the wild one.

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Effect of adult food and physiological status of adult melon flies, Dacus cucurbitae COQUILLETT, on the flight ability was studied. Flight duration of the flies decreased remarkably as the starvation period increased. These phenomena were more conspicuous for the 15 and 30 days old flies than for the 5 days old ones. These results suggest that the flies should search and take food every time. No adverse effect of starvation was observed on the flight velocity. Flight duration was the longest when the ratio of protein hydrolysate and sugar in adult food was 1:5 and it decreased with the content of protein hydrolysate. These results show that protein hydrolysate is an important element for the flight ability of the melon fly. Flight duration in non-copulated 15 and 30 days old female was longer than that in the copulated ones. However, such differences were not observed in male flies. Sexual difference in the flight performance seems to be natural since females mate a few times but males mate many times through out their lifespan. Flight duration of flies which had oviposited was shorter than that of flies which had not oviposited, suggesting that the dispersion ability of the melon fly may increase after the oviposition.

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Seasonal occurrence of microsporidia in moths of the lawn grass cutworm, Spodoptera depravata, was investigated from May to October in 1984. Moths were collected by light traps at Sayama, Chigasaki, and Sagamihara in the Kanto district. The percentage of infected moths increased as the season advanced i.e. from 9.2% in spring to 14.5% in the autumn generation, while the spore density of microsporidia per adult decreased as the generations advanced. The spore size of the microsporidia isolated in the present investigation ranged from 3.37 to 4.46μm by 1.85 to 2.50μm. Of seven stocks selected from these microsporidia, three stocks were infectious to the silkworm, Bombyx mori, and two of the above three induced a systemic infection similar to that of Nosema bombycis.

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To determine whether Thrips palmi KARNY can overwinter in fields, the survival period of the adults and second instar larvae was investigated at the constant temperatures of 0°C, -5°C and -10°C, and fluctuating temperatures of -5°C-5°C (mean temperature, 0°C), respectively. The summer populations were susceptible to the exposure to low temperatures, while the winter populations were more tolerant to the low temperatures. Winter populations were able to tolerate constant temperatures of -10°C and -5°C for one day and one week, respectively. Maximum survival period of the overwintering adults and second instar larvae exposed to a constant temperature of 0°C with egg-plant as food was 11 days and 16 days, respectively, while under the fluctuating temperature conditions, the period was 28 days and 18 days, respectively. Thus, daily temperature fluctuations prolonged the survival period of the overwintering adults at a low temperature. The larvae could not undergo ecdysis or metamorphosis under fluctuating temperature conditions which simulated the changes of the winter air temperature in the fields of Okayama. Consequently, it is suggested that T. palmi may not be able to overwinter under natural conditions in the fields of the southern part of Okayama Prefecture.

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Reproductive ability in dicofol susceptible and resistant strains of the two-spotted spider mite, Tetranychus urticae KOCH, of the same origin was tested by the method of leaf disk at the temperatures of 20°C, 25°C and 30°C. Both the survival rate and egg production in the susceptible strain tended to be higher than in the resistant one at 25°C and 30°C. Hatchability of the eggs was somewhat higher in the susceptible strain than in the dicofol resistant one at each temperature, and the intrinsic rate of natural increase (r_m) was also higher in the susceptible strain than in the resistant one at each temperature. Emergence rates in both the 1st and 2nd generations were partially higher in the susceptible strain than in the dicofol resistant one, and mean no. of eggs per female of the susceptible strain was also larger than that of the dicofol resistant one at 25°C. Developmental period of the pre-adult stage was slightly shorter in the susceptible strain than in the resistant one at each temperature. These results indicate that the dicofol resistant strain showed lower values of fitness than the susceptible one under an acaricide-free environment and that the susceptibility of the dicofol resistant strain recovered slowly after relaxation of the dicofol pressure.

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The LC₅₀ values of cartap and bensultap against the young snail, Pomacea canaliculata were 2.0ppm and >10ppm at 48h, respectively and the feeding of rice plant by the young snails was completely inhibited at a dose of 0.31ppm for both insecticides. The LC₅₀ values of cartap and bensultap against the adult snail were 1.9ppm and 10ppm at 48h respectively and feeding of rice plant by the adult snails was completely inhibited at a dose of 0.31ppm for cartap and 0.63ppm for bensultap. The feeding inhibitory efficiency of both insecticides was very high. In the submerged application of cartap and bensultap granules (4kg/10 a), feeding by the young snails was completely inhibited during 15 days after treatment. In the case of nursery box-treatment with cartap and bensultap granules (60g or 100g/box), feeding by the adult snails was almost completely inhibited during 21 days after transplanting. These results suggest that cartap and bensultap are able to protect the rice plant from feeding by the snails for about 3 weeks in paddy field.

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Detailed characterization of the “Giant egg” (Ge, 1-14.0) mutant in Bombyx mori was performed using the female progeny of the cross T (W; 3) Ze/os+sch_??_×+Ge+/os+sch_??_ as materials. Females in this mating line are characterized by the female-limited larval marking of “Zebra”, and the os sch larvae are normal-egg formers while the ++ are giant-egg formers with rare, less than 1%, exceptional forms which were introduced through double crossing over phenomenon. The main characteristics of Ge were as follows. 1) Size of Ge egg based on measurements of the major and minor axis was larger than that of a normal egg by 1.18 and 1.12 times, respectively. 2) Weight of Ge egg was 1.44 times heavier than that of a normal egg. 3) Number of eggs produced by a Ge female was 33 percent lower than that of a normal female. 4) Giant egg contained 1.53 times more yolk protein than a normal egg, with no qualitative differences. 5) Weight of the body and of the ovary during pupal development showed no difference between Ge and normal. It may be inferred that, in Bombyx mori, some regulatory mechanism acts in the oogenesis to keep the total amount of egg materials produced by a female at a definite level through the control of the size and number of eggs.

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Migration of lepidopterous insects was investigated in Nara during the period 1984 to 1986, and in Okayama during the period 1985 to 1986 using the migration trap originally designed by WALKER (1978). When two traps are set at right angles to each other, insects can be caught from all the four directions because the trap has two openings in opposite directions. On the top of Mt. Katsuragi, 950m in elevation in Nara, both traps were set in a NE-SW direction to catch the migrant skipper, Parnara guttata which migrates annually to the south-west direction in the autumn. The number of skippers caught through the opening in the north-east direction was significantly larger than that in another direction. In Okayama, two traps were set so as to open in four directions (N, S, E and W). Lepidopterous insects of eighty two species were caught throughout these periods. The flight direction of six species, Cnaphalocrocis medinalis, Hymenia recurvalis, Pseudoaletia separata, Spodoptera depravata, Ostrinia furnacalis and Hodjina biguttula was significantly biased to the west in the summer or autumn. It is known that the former three species migrate to the north-east direction in early summer in Japan and China. The results of the present studies suggested that these species might fly to the opposite direction in the autumn.

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Biological control experiments of Tetranychus urticae KOCH by use of the resistant strain (hereafter called DAS-strain) of Phytoseiulus persimilis ATHIAS-HENRIOT which was introduced from West Germany were conducted on cucumber plants cultivated in a vinyl house. Furthermore, a system simulation by micro-computer was designed to develop a realistic model of the predator-prey system under pesticide spraying conditions. Resistance level against fenitrothion in the DAS-strain of P. persimilis increased with the replication of the fenitrothion treatment. However, the level of resistance diminished to the level before the selection by the pesticide, when the interval of the selection was extended to about 4-6 months. Under chemical spraying conditions, i.e. 7 applications of fungicides and 4 applications of fenitrothion, the DAS-strain predacious mites effectively controlled the spider mite population when they were introduced at the ratio of P. persimilis female: T. urticae female=1:10. Furthermore, the predator could more effectively suppress the prey population when fenitrothion was first sprayed on the 7th day or 10th day after the predator introduction. In these two cases, the leaf damage index (LDI) did not exceed a value of 2.0 during the course of the experiments, although the LDI level at the time of the predator introduction was 1.3. There were two kinds of discrepancy between the experimental data and system simulation. One was concerned with the mite developmental speed dependent on the temperature, and the another with the loss of the predators at the time of introduction. When the value of the mean daily temperature decreased to 85% of the observed values and the number of predators introduced decreased to 80%, the model successfully simulated the processes and results of all the experiments. If the changes in the driving variables could be controlled in the future, this model may become useful to predict the effectiveness of the DAS-strain of P. persimilis as an agent for the biological control of spider mites under pesticide spraying conditions.

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Developmental response of larvae of the oriental corn borer, Ostrinia furnacalis, to the autoclaved corn plant parts at different growth stages was examined in relation to the chemical composition of the corn parts. Higher levels of nitrogen-containing fractions-free amino acid, soluble protein, and total protein fractions-were observed during the vegetative growth stages, whereas the contents of sugars and digestible carbohydrates increased as the growth stage of the corn plant advanced. Thus, C/N ratio values (total soluble sugar content/crude protein content) in corn plants ranged from below the unity at the young vegetative stages to higher values at more advanced stages. The larvae fed on the corn plant parts with low C/N ratios grew faster than those on corn parts with higher C/N ratios. The weight increment of larvae on the corn parts with C/N ratios ranging from 1 to 2 was the highest while that of larvae on foods with ratios below unity or over 3 was lower.

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Most of the 2nd and 3rd generations of the Morioka population of the apple leaf miner developed to diapausing pupae under the photoperiodic regime of 13h or less at 15°C and 20°C. In the 1st generation, however, the percentage of diapause was about 50% or lower under the same photoperiodic-thermal conditions. In two hybrids between the overwintered (O) and the 1st (I) generations, the photoperiod-% diapause curve in the progeny of O_??_×I_??_ closely resembled that of the 1st generation. On the other hand, the curve in the reverse crossing (I_??_×O_??_) was similar to that of the 2nd generation. From these results, it was suggested that the information for the inhibition of the induction of the diapause acquired within the body of the overwintering female during the course of her development, was transmitted maternally in the 1st generation eggs. As the information disappeared after the 2nd generation, it is considered that the information did not affect the genetic sensibility for photoperiod, but was a secondary and temporary factor. The small differences observed between the 2nd and the 3rd generations, can be mainly ascribed to differences in the leaf age or number of instars during the sap-feeding larval stage. The decline of the photoperiodic responses in the 1st generation was also observed to some extent in all the other local populations examined; Asahikawa, Kanazawa, Suzaka, Hamamatsu and Amagi.

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When both Bombyx densovirus type 1 (DNV-1) and type 2 (DNV-2) were fed to the larvae of the silkworm, B. mori, the two viruses interfered with each other in the infection of the insect. The degree of interference varied with the relative concentration of the two viruses inoculated. In order to localize the infection with the two viruses in the midgut epithelium, histological sections were performed and processed for immunoperoxidase double staining with different chromogenic substrates. The results revealed that most of the columnar cells were infected with either DNV-1 or DNV-2 and the other columnar cells were doubly infected with the two viruses. These results indicated that there is a mutual interference between the two densonucleosis viruses in the infection of the silkworm at the cellular level as well as at the organism level.

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Trissolcus plautiae is a solitary and dominant parasitoid of the brown-winged green bug, Plautia stali which lays 14 eggs in compact masses. Laboratory studies were carried out to investigate the ovarian development, fecundity and sex allocation. T. plautiae was found to be a synovigenic species, that is, newly emerged females had only a few mature eggs in their ovaries, produced 14.8 mature eggs on the average after one day and a full complement was reached after 4 days. During first several days females laid nearly 14 eggs daily even when large host egg masses artificially constructed were provided to the wasps. However, in such a case, the mortality of the progeny in hosts was high. It was concluded that the primary sex ratio was 0.07 and the sex allocation into a host egg mass of 14 eggs was one male and 13 females. Based on the sex allocation data and net reproductive rate, T. plautiae appears to be able to parasitize 8-9 host egg masses consisting of 14 eggs throughout the life time. The present results suggest that the ovarian development and oviposition rate of T. plautiae are closely related to the typical size of a host egg mass.

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Position of egg-masses deposited in autumn by the viburnum leaf beetle, Pyrrhalta humeralis (CHEN), was observed on a hedge of host trees in March, 1984, and the oviposition behaviour of the beetle was analyzed in relation to the age of the branches of the host tree. Although no definite vertical preference was observed among the branches on the tree, beetles deposited more than half of their egg-masses on the one-year old branches, and the frequency decreased when the branches were older. The majority of the egg-masses was deposited within a range of 10mm from the nearest buds, and in relation to the distance from the terminal tip of branches, more than half (or the majority) of them was located within the distance of 20mm (or 60mm), respectively.

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The number of overwintering egg-masses of the viburnum leaf beetle, Pyrrhalta humeralis (CHEN), and subsequent feeding damage by larvae were investigated following three different experimental treatments (summer pruning, winter pruning and no pruning) on a hedge of host plant trees, Viburnum awabuki K. KOCH. Conventional pruning practices were conducted in late July, when the elongation of the shoots stopped, and in mid-March, just before the eggs started to hatch, for the summer and winter pruning operations, respectively. The number of egg-masses left on the tree was observed in late March, and the leaf damage caused by the larvae was estimated in the following mid-June. Results showed that significantly fewer egg-masses and lighter leaf damage were observed under both pruning operations on the north side of the hedge, where shoot growth was extensive. On the south side, shoot growth was minimal and thus the effects of the pruning operations were not significant although lighter leaf damage was observed during the winter pruning operation.

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Phytoseiid mite populations were collected on citrus groves, or windbreaks composed mainly of Yew podocarpus or Japanese cedar around the citrus groves, and on grapevines in glasshouses and vinyl-houses in western Japan. Susceptibilities of the phytoseiid mite populations to methidathion, carbaryl, salithion and maneb were compared. Susceptibilities to methidathion of the Amblyseius eharai AMITAI et SWIRSKI populations collected from Kawakami, Yahatahama and Higashino, Matsuyama in Ehime Prefecture and other three habitats were low. The resistance factor at the LC₅₀ value of the Higashino, Matsuyama population (R) to the susceptible one (S) was 9.3 (13.0ppm/1.4ppm). Susceptibility to methidathion of the A. sojaensis EHARA population collected from Yakura, Iyo (R) in Ehime Prefecture was the lowest, and the resistance factor was 6.4 (43.0ppm/6.7ppm). In A. longispinosus (EVANS), the susceptibilities to methidathion were comparatively high. Susceptibilities to carbaryl of the A. eharai populations collected from Higashino, Matsuyama (LC₅₀=82.0ppm) and other seven habitats were low. Susceptibility of the A. sojaensis population from Yakura, Iyo (R) to carbaryl was low, and the resistance factor was 4.7 (53.4ppm/11.3ppm). In A. longispinosus (EVANS), the susceptibilities to salithion of the populations collected from Ichinomiya, Okayama, and Akitsu, Hiroshima Prefecture were low, and the LC₅₀ values of the two populations tested were nearly 400ppm.

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Susceptibility to dicofol of the two-spotted spider mite, Tetranychus urticae KOCH, selected with dicofol decreased relatively slowly. The decrease of the susceptibility to chlorobenzilate, the chemical structure of which was similar to that of dicofol and phenkapton (organophosphate), was also observed along with the decrease in the susceptibility to dicofol. Especially, the susceptibility to phenkapton in the dicofolselected two-spotted spider mites was more significantly reduced than that to dicofol. On the other hand, the changes of susceptibility to tetradifon and chinomethionate were negligible. These results suggest the presence of a high level of cross resistance between dicofol, and chlorobenzilate and phenkapton.

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The role of free amino acids in the mechanism of barley resistance to cereal aphids was studied. Total free amino acid concentrations in the leaves of the resistant barley lines tested were higher than those of the susceptible lines. Furthermore, the low value of some amino acids, but the high proportion of the aspragine fraction containing glutamic acid appeared to be associated with the resistance to the aphids.

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