The photoperiodic induction of larval diapause of the box-tree pyralid, Glyphodes perspectalis (WALKER) collected from four localities in Japan showed typical long-day response curves. The critical photoperiods were 14h 20min for the Miyagi and Fukuoka (Mt. Kosho; 862m above sea level) populations, respectively, 13h 50min for the Tokyo-Chiba population and 13h 40min for the Kochi population at 20°C, showing a geographical cline. The critical photoperiods for the photoperiodic response in the offspring of overwintering generation of the Tokyo-Chiba population showed large individual variations. Moreover the critical photoperiod varied with temperature conditions, being higher at 15°C than at 25°C. When reared singly or in a crowded condition on three kinds of host plants, Buxus microphylla, B. sempervirens and B. microphylla var. insularis, their photoperiodic responses were typical long-day types except in the crowded condition on B.m. var. insularis where a high level of diapause was induced even under long-day conditions. This result suggested that dietary conditions were acting as regulating factors of diapause induction. The sensitive period for the photoperiodic induction of diapause lies between the first and third instar, especially the latter half. Photothermographs for four localities suggest the occurrence of two to four generations per year depending on the locality. For the Tokyo-Chiba population the predicted life cycle fitted well with the actual field observations.

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Laboratory and field experiments were conducted to study the infectivity and propagation of Steinernema kushidai on Anomala cuprea larvae. The nematode-infective juveniles (JIII) showed higher infectivity for the 3rd instar than the 2nd and 1st instar of A. cuprea. When JIII were inoculated on the 3rd instar, as much as ca. 30, 000 JIII were produced per larva on average. The JIII production increased with increased insect size. Survival of JIII was also investigated under various conditions. The survival rate of JIII stored in water exceeded 50% at 15°C after 3 months, and decreased to 50% in a month or less at 4°, 10°, 20° and 25°C, and to below 10% at 4°C. In sterilized soil, nematode infectivity remained high for up to 6 months at 15°C. When the JIII were applied once to the soil of a peanut field in mid-April at the rate of ca. 10⁶/m², the infectivity remained high enough to kill A. cuprea larvae for 8 months, but it became very low during winter. The nematode was adversely affected by treatments with insecticides (Diazinon and MPP, 500-2, 000ppm), but not with fungicide (Thiophanatemethyl, 500-2, 000ppm) and with herbicides (CAT and Glyphosate, 5, 000-20, 000ppm). Twenty minutes or longer exposure of the nematode suspension to sunlight resulted in decreased survival of JIII. Metarhizium anisopliae had no effect on the nematode.

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The seasonal prevalence of Plusiinae species was investigated every week in a cabbage field at Hitsujigaoka, Sapporo (43°30″N, 141°25′E) from 14 June to 4 December 1991. Only three Plusiinae species: the silver Y moth (Autographa gamma), the Asiatic Common Looper (A. nigrisigna), and the cabbage looper (Trichoplusia ni) were collected. There were few individuals of the latter species. The number of immature stages of A. nigrisigna increased twice in June and August, then decreased during and after September. A. gamma increased three times in June-August, September and November. The last population of A. gamma was relatively big until the beginning of December.
A similar tendency was revealed by using sex-pheromone traps every day from May to November 1991. However, many more A. gamma were captured than A. nigrisigna.

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The seasonal occurrence of the Citrus Red Mite, Panonychus citri (MCGREGOR), on an evergreen host tree, Irex crenata THUNB. was investigated. The population increased rapidly during the spring and peaked in late May. Towards late May and early June, many adult females drifted on webs from the I. crenata tree, and some reached a neighboring Japanese-pear orchard.
The dispersed mites maintained their population density around the landing sites until summer, and then gradually increased in number in the pear orchard. On pear trees near the Irex tree, the number of mites increased from early summer and eventually produced bimodal population peaks in summer and autumn. On the other hand, mites on trees a long way from the source tree showed a low increase in numbers until late August, but then increased rapidly in autumn causing a single peak.

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The seasonal population dynamics of a phytophagous mite (Tetranychus urticae (red form)) and its natural enemies were observed on a leguminous arrowroot, Pueraria lobata, in 1989. The mite population density showed a typical bimodal pattern with two peaks in June and October. A staphylinid, Oligota kashmirica benefica (O.k. benefica) was the most abundant insect predator, and its population trend was closely synchronized with that of its prey mite. Another Oligota species, O. yasumatsui, was observed at low density throughout the season. Among predacious mites, Amblyseius longispinosus was predominant and seemed to play a significant role as a natural enemy at low prey densities.
Laboratory studies were conducted to clarify the predacious ability of O.k. benefica on the spider mite. Larvae of the beetle preyed on an average of 379.6 eggs of T. urticae (green form) each during the larval period at 25°C. The mean longevity of adult females was 73.9 days, and the average total number of prey consumed by an adult female was 7, 478.8 eggs. Females oviposited an average of 226.6 eggs in their life. These results suggest that the population dynamics of the beetle on arrowroot are affected by the population densities of spider mites, and the beetles have a significant effect on spider-mite populations.

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The host preference between eggplants (Solanum merongena L.) and cucumbers (Cucumis sativus L.) in spring, and the susceptibility to fenitrothion of populations of the cotton aphid, Aphis gossypii GLOVER, overwintered on shepherd's purse (Capsella bursa-pastoris M.), speedwell (Veronica persica P.) and rosemallow (Hibiscus syriacus L.) were investigated in closed plastic minihouses at Higashihiroshima in Hiroshima Prefecture from 1988 to 1990. Two biotypes with different host plant preferences for eggplant and cucumber were observed in field populations overwintered on winter host plants such as shepherd's purse, speedwell and rosemallow. Populations transferred from eggplants to overwintering host plants preferred the original host eggplant to cucumber in the early spring. Populations transferred from cucumbers to overwintering host plants preferred the original host cucumber to eggplant. Susceptibility to fenitrothion was higher in the populations on eggplants than those on cucumbers.

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The surface structure of the eggshell of the Giant egg mutant (Ge) of Bombyx mori was observed by a differential intereference contrast microscope. Four spatially-differentiated surface regions, called anterior (micropyle region taking form of single flower with many petals), posterior, dorsal plus ventral, and lateral (unit of network patterns each taking shape of regular or irregular polygon which reflects boundary of follicular epithelial cell), were found on the Ge mature eggshell as on the normal eggshell. However, the size of the Ge polygon at the lateral region was smaller than that of the normal eggshell, and the number of knobs within the Ge polygon were fewer than in the normal polygon. This result suggests that the Ge egg is made by an increased number of follicle cells, each of which secretes chorion over a smaller surface area.

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Factors influencing egg mortality in Aphis gossypii hibernating on Hibiscus syriacus L. were examined. Observations on 380 hibernating eggs in the field showed that 42% hatched successfully next spring and that 87% and 6% of egg mortality were due to atrophy and falling from the branches, respectively. Egg atrophy occurred in the field from December to February. Oviparous females isolated without males in the laboratory often laid unfertilized eggs in early November. Fertilized eggs turned glossy black 7 days after oviposition, but unfertilized ones turned dark yellow or transparent except at the central part and atrophied 6 weeks later. Few of the eggs laid by mated oviparous females died of atrophy within 6 weeks after oviposition. These results suggest that egg atrophy in the field is caused by a considerable number of unfertilized eggs in hibernating eggs.

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