Sex pheromone production in the female moth, Chilo suppressalis in the early scotophase was inhibited by decapitation 2hr before light-off in the previous photophase. Injection of head extracts with saline from females decapitated between 1.5 and 2hr after light-off to females decapitated between 2 and 1hr before light-off restored the pheromone titre, indicating that a hormone-like substance from the female cephalic organs controls the pheromone production. In addition, the presence of the substance was shown to be necessary for the continuation of pheromone production, since decapitation at various times after light-off resulted in differences in the pheromone titres which depended on the time interval between light-off and the decapitation. Neural control from the head via the central nervous system for the pheromone production was ruled out based on results of severance of the ventral nerve cord. Calling was also inhibited by decapitation. However, it remains to be determined whether the mechanism controlling calling was different from that controlling pheromone production.

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Adults of the spotted cutworm, Xestia c-nigrum LINNÉ, were caught in areas at different altitudes in central Iwate, Honshu (about 40°N). Their offsprings were reared under constant temperatures ranging between 12.5 and 30°C with a daily illumination of 16hr. These local stocks were compared in their developmental characters with one another and with the lowland strain from central Hokkaido (about 43°N). In general, developmental zero for the immature stages was estimated to be between 7.0 and 8.5°C, and some larval and pupal mortality occurred at 30°C. Total developmental duration was longest in the univoltine Iwate-highland stock, shortest in the bivoltine Hokkaido stock, and intermediate in the bivoltine Iwate stocks. Among the last ones, there were few significant differences in developmental time, in spite of the fact that they originated from areas with a wide altitudinal range between 150 and 1, 150m. These three groups also showed different thermal responses in pupal weight. The short developmental time in the Hokkaido strain and the univoltine life-cycle prevailing in the Iwate-highland strain could be interpreted as being associated with genetic adjustment to the low temperature in their original localities. However, the conformity in developmental time among the bivoltine Iwate strains cannot be related to the diverse climates characterizing their original grounds of different altitudes. This puzzling phenomenon may be ascribed to the local altitudinal migration by adults as suggested for the species.

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Sex-pheromone components and related compounds released by virgin females of Adoxophyes sp. (smaller tea tortrix, STT) and Adoxophyes orana fasciata (summer fruit tortrix, SFT) were collected by the filter-paper adsorption method and glass-wall adsorption method. Collection efficiency of the pheromonal compounds by the filter-papar method was about 10 times that by the glasswall method. However, the ratio of pheromonal components was not different between the two collection methods. Amounts of the total compounds released from STT females were about 3 times the amounts from SFT females. Sixteen acetates and 10 alcohols were detected in STT and 11 acetates and 7 alcohols in SFT females. Of these compounds, undecenyl acetate, 10 methyldodecyl acetate, tridecyl acetate, 12-methyltetradecyl acetate, pentadecyl acetate, undecanol, undecenol, pentadecanol and hexadecenol observed in STT were not detected in SFT. Tridecanol found in SFT was not detected in STT.

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Morphological changes of the larval integument in the last larval instar of Bombyx mori were investigated by light and electron microscopy, and correlated with known ecdysteroid levels in the haemolymph. About 15 fibrous layers were observed in the larval cuticle of 5th instar larva which had just exhibited ecdysis. During the feeding stage, the epidermis secreted 7-12 fibrous layers day by day to reach a total of about 70 layers when the larva began to wander. When the small amount of ecdysteroid began to appear in the haemolymph (about 8hr before wandering), intercellular spaces started to appear in the epidermis which became more prominent throughout the wandering and spinning periods. At the same time, amorphous electron-dense bodies (considered as ecdysial droplets) appeared at the cell border adjacent to the overlaying endocuticle. Such amorphous bodies seemed to move to the inner layer of the endocuticle to form the ecdysial space during the wandering stage. Distinct larval-pupal apolysis which was observed 12hr after the gut purge become more pronounced throughout the spinning period. Well developed epidermal microvillae observed during the feeding period degenerated after the cessation of feeding. However, the microvillae began to develop again aroud the critical time of ecdysone secretion from the prothoracic glands. Deposition of pupal cuticle started around the time of completion of cocoon spinning. Based on the relationships between the epidermal changes and ecdysteroid levels in the haemolymph, a developmental time-table was presented for the last larval instar of the silkworm, Bombyx mori.

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Emmalocera sp. (Lepidoptera: Pyralidae) is a monophagous stem borer of the barnyard grass involving two varieties, Echinochloa oryzicola and E. crus-galli var. crus-galli, which grow in paddy fields. Factors responsible for the onset of diapause in Emmalocera sp. were investigated with reference to food quality, i.e. varieties and growth stage of the host plant. Percentages of larvae which underwent diapause differed between varieties and plant ages of Echinochloa. The type of photo response of Emmalocera sp. was long-day type. Critical day-length located between 12 and 15hr. When larvae were reared under different day-lengths around the critical one, most of the larvae developed pupation on young host plants, while those on the old ones underwent diapause. The conversion stage from vegetative to reproductive phase differed between the varieties, i.e. 8-11th plant age in E. crus-galli var. crus-galli, 10-13th in E. oryzicola. Consequently diapause was induced earlier in the larvae developed on the former than the latter at the critical day-length. It was discussed between the number of generations of Emmalocera sp. in the paddy fields and two barnyard grass varieties.

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In the middle of May, 1983, 228 overwintered adults of the brown-winged green bug, Plautia stali SCOTT were collected from a mulberry field, and were reared in containers in an insect chamber at 22±1°C and under a 16L-8D photoperiod regime. In each rearing container two females and two males were supplied with several raw peanuts and water. Rapid decrease in the survival rate of males and females was observed 50 days after the start of the rearing. Mean survival duration of males and females was 85.9±34.8SD and 90.6±31.5SD days, respectively. The average number of eggs and egg masses deposited by a female was estimated to be 461.6 and 36.4, respectively. The daily number of eggs deposited by a female increased during the first 20 days and fluctuated within the range of 6.5±0.7SD eggs during the next 50 days, then it decreased subsequently. The net reproductive rate (R₀) was estimated at 231.7. Although the mean size of the egg masses was 12.7±4.9SD, egg mass size of 14 was maximum in frequency. Therefore, it is concluded that the typical size of the egg mass was fourteen in this species. The mean size of the egg mass slightly decreased with the adult age. The frequency of egg masses deposited on different sites in a rearing container also varied with the adult age. Although most of the egg masses were deposited on two-folded papers and on the surface of the rearing container, the frequency on the former increased and it decreased on the latter as the adult became older. The oviposition mostly took place during the time between 3hr before and 1hr after the beginning of the dark period.

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Differences in the egg density, oviposition period, and survival rate of mature larvae of the oriental corn borer, Ostrinia furnacalis, on corn grown at conventional (CFL) and double fertilizer levels (DFL) in field plots were analyzed in Morioka in the northern part of Japan, during the period 1972-1975. Corn plants in fields with DFL were taller, occurred in a larger number of leaves, and grew faster than those in fields with CFL. The oviposition period of the borer was very similar in the first and second generations at both fertilizer levels. The egg density was higher and the larvae grew a little faster in fields with DFL than in those with CFL in the first generation. The survival rate during the larval stage was found to be nearly identical for both fertilizer levels, so that the density of the mature larvae in fields with DFL was higher than that in fields with CFL. In the second generation, however, the egg density for CFL was higher than that for DFL, and consequently the density of the mature larvae for both fertilizer levels became similar, because the survival rate during the larval stage in fields with DFL was higher than that in fields with CFL. Based on these results, it is concluded that the occurrence of the oriental corn borer varied depending on the differences in corn growth which was associated with differences in the fertilizer levels therefore corn grown at the double fertilizer level contributed to the increase of the corn borer population.

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Population dynamics of Triops longicaudatus LECONTE was studied from 1981 to 1982 in a paddy field of Hiroshima Agricultural College at Higashi Hiroshima City, Hiroshima Prefecture. Four plots were established in a paddy field. Initial densities of young forms in 1982 were 1/5-1/10 higher than those in 1981, while the densities of eggs were almost equal in the soil, presumably due to the low hatchability of the eggs associated with the high water temperature in 1982. Predators were seldom observed during the study period. Mortality rates were density-independent. Carapace length growth was density-dependent, so that the mean body size in 1982 was larger than in 1981. It was estimated that the egg production per female in 1982 was higher than that in 1981. No differences in total egg production per plot were observed between 1981 and 1982. About 60% of the eggs did not hatch after flooding and ploughing and were carried over to the next season. It is suggested that the population of T. longicaudatus was potentially stable in each generation, but that it became unstable due to the influence of external factors, such as weather conditions, pesticide application and water level management of the paddy field.

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Leaves of rice plants at early growth stages were artificially injured by cutting them off with scissors to simulate the feeding of the rice plant weevils. The effect of leaf injury on the yield loss was investigated. The yield loss did not occur when the leaves were artificially injured only once 7 days after transplanting, although 100% of the leaves were injured. Treatment in which 30% leaf cutting carried out 4 times at 5 days intervals 7 days after transplanting caused no yield loss. When the ratio of leaf injury ranged from 50% to 70%, treatment 12 days after transplanting was mainly responsible for the yield loss. The following regression equation was obtained y=24.86+0.19x-0.01x²+0.000056x³ (r²=0.55), where y refers to the weight of rice grains (g) per hill and x is the percentage of injured leaves. From this equation, the maximum injury level that would not cause yield loss was estimated to correspond to about 50% leaf injury per hill. It was considered that the yield loss of rice plants caused by the leaf injury resulted from the reduction in the number of panicles.

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The numbers of bark beetles (Ips cembrae (HEER)) attacking the fenitrothion sprayed logs decreased with increasing the concentrations. Residues from bark sample analysis indicated that fenitrothion remained in the outer bark at effective concentrations over 3 months.

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Adelges japonicus infests Picea jezoensis and makes a gall. The experiment was carried out to know when the stimulus causing a gall was given. The fundatrix of A. japonicus gives the stimulus. Without fundatrices, a gall was not formed only by the 2nd generation nymphs.

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Orientation of Plusia agnata males to the conspecific virgin females confined in a small mesh cage was observed overnight in a walk-in field cage. When the females started calling, the male approached from obliquely above toward the lower surface of the female cage, and continuously hovered up and down underneath the cage. Sometimes the male alighted on the lower edge of the cage, curved his abdomen toward the females and everted his hairpencils. Meanwhile the male flew away. The peak orientation of the males occurred twice in a night probably corresponding to the two peaks of the calling activity of the females. Males were caught in a water pan trap baited with virgin females set in the field cage because of their flight behavior underneath the female cage. The peak catch of males in the trap occurred once at the first peak of orientation.

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