The mitochondrial gene sequences of 682 bp encoding cytochrome oxidase subunit II (COII) were deter-mined for seven species of the genus Ostrinia in Japan and a single species from North America. The ob-served sequence differences showed a strong bias toward transitions at the third codon positions, which is typical for closely related species of insects. Close relationships among the eight Ostrinia species were also indicated by the low levels of sequence divergences (0.15-7.23%). The estimated phylogenetic tree of the eight sequences supported two previously proposed taxonomic groups, i.e. the bifid uncus group (O. palustralis and O. Iatipennis) and the trilobed uncus group (O. furnacalis. O. orientalis. O. nubilalis. O. scapulalis. O. zaguliaevi and O. zealis), in the Ostrinia species examined. Species of the two groups were differentiated from each other with 4.69-7.23% sequence divergence. However, the relationships between the COII sequences within the trilobed uncus group were not concordant with the taxonomic classification, which divides the trilobed uncus group into two subgroups. Based on the observed sequence divergences (0.15-2.38%), the six species of the trilobed uncus group were considered to be extremely closely related to each other. The COII sequence is considered as a suitable source of characters for inferring phylogenetic relationships in Ostrinia species.

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A change in genetic structure with an increase of population density in Panonychus citri was analyzed by laboratory experiments focusing on the inbreeding coefficient (F) and spatial distribution. Genotype frequencies of an esterase locus, a-Estl, in F₁ females after mating in various population densities suggested that P. citri mated randomly. Adult females introduced to small citrus seedlings laid most eggs on the leaves on which they were set. The majority of immature offspring stayed on the leaves where they hatched. Females with different homo genotypes were introduced on leaves at the top and bottom of seedlings separately. The inbreeding coefficients of the developing populations were kept high for at least a month. A Iinear relationship was observed between mean density of adult females and F. From these results, we concluded that the aggregated egg production by adult females and low dispersion rate in the immature stages strongly restricts hybridization among breeding Patches of this secies.

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Based on the amino acid sequence of Allomyrina dichotoma defensin, degenerate primers were synthesized, RT-PCR was done to clone a defensin cDNA and a 114-bp fragment was obtained. The complete nucleotide sequence was determined by sequencing the extended cDNA clone by 3' and 5' RACE. The deduced amino acid sequence of the mature portion was identical to that of the purified defensin. Tissue-specific gene expression analyzed by Northern blotting showed that the main sites for defensin gene expression were the fat bodies and hemocytes. The time course of defensin gene expression indicated that expression peaked at 8 to 12 h in larvae injected with Escherichia coli. An analysis of defensin gene expression induction by E. coli or Staphylococcus aureus in the fat body and hemocyte by RT-PCR showed that E. coli induces defensin gene expression more effectively than S. aureus in both tissues.

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Infestation of sugarcane by the pink borer, Sesamia inferens (Walker) (Lepidoptera : Noctuidae), parasitism of the pink borer by Cotesia flavipes (Cameron) (Hymenoptera : Braconidae) and host-parasitoid relationships were examined on Okinawa Island over a period of 4 years. Bimonthly surveys indicated that infestation by the pink borer had two peaks, one in April/May (20.5 to 29.3%) and the other, in August (22.2 to 29.5%), whereas parasitism of the pink borer had only one peak in August (61.2 to 80.1%). The density of C. flavipes at time t depended most strongly on the density of the pink borer at time t (r=0.77 to 0.84), whereas, the density of the pink borer depended most strongly on the density of C. flavipes at time t-3, i.e., 1.5 months earlier (r= -0.29 to -0.44). It was notable that the mean number of parasitoids that emerged from a single host varied seasonally, being smallest in February (17.6 to 26.8) and largest in August (48.8 to 59.2). A positive correlation between the mean number of emerged parasitoids and the mean temperature in each month (r=0.87) suggested that the number of eggs oviposited by a female per host was influenced by temperature.

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Fundatrix populations of the aphid Uroleucon nigrotuberculatum were studied for 4 years on an observation plot of the goldenrod Solidago altissima. Oviposition sites were not restricted to goldenrod rosettes. The feeding site of hatched larvae was the bundle of unstretched leaves which was located at the center of the goldenrod rosette. Due to underestimation of the egg population, the mortality of hatched larvae before their arrival at the feeding site could not be calculated. Mobile form-fundatrix populations consisting of larvae and adults gradually decreased during the period to about 40% of the maximum. During that period diurnal natural enemies were inactive. The spatial distribution of mobile form-fundatrix populations was contagious. The contagiousness was maintained by inter-plant movement and a tendency for aggregation in larvae and adults.

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The production of courtship song, 87.9±8.5 ms in duration, by male Euscepes postfasciatus appears to be one step of the behavioral sequence leading to copulation. Females which had perceived the courtship song responded to this signal by remaining stationary and allowing males to mate, but unreceptive females or males produced disturbance songs, 22.5±1.9 ms or 16.9±2.2 ms in duration, respectively, and/or made jerky movements. When weevils were held with tweezers, they produced the disturbance song. This song may have a defense function.

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We studied the response of two populations of the predatory mite, Amblyseius womersleyi, toward volatiles of kidney bean leaf infested by Tetranychus urticae in a Y-tube olfactometer. The predators collected in Kyoto (A . womersleyi-Kyoto) showed a significant preference for infested leaf volatiles to uninfested leaf volatiles, whereas the predators collected in Shizuoka (A . womersleyi-Shizuoka) did not. This difference was not due to a difference in their feeding experiences but to a genetic difference, since both populations were tested after being reared under the same laboratory conditions for more than three months (more than 10 generations) . We then compared the performance and behavior of the two populations. The fecundity and oviposition periods of A. womersleyi-Kyoto were not significantly different from those of A. womersleyi-Shizuoka. However, the dispersal of A. womersleyi-Kyoto from a T. urticae-infested bean leaf culture occurred earlier than that of A. womersleyi-Shizuoka. The lower dispersal ability in A. womersleyi-Shizuoka compared that of A. womersleyi-Kyoto is attributed to a difference in ability to distinguish infested plant volatiles from uninfested ones.

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Pheromones released by adults of the bean bug, Riptortus linearis (Fabricius), were investigated using adultbaited traps on Okinawa Island. Males confined in an insect cage attracted adults of both sexes and 2nd stadium nymphs in a field test, which indicates that the male bug releases an aggregation pheromone. On the other hand, only males were caught in a trap baited with females. This fact suggests that the female bug releases a sex pheromone.

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Cotesia glomerata showed the same level of intensive antennai searching on damage of a Rorippa indica leaf infested by not only Pieris rapae larvae (host) but also P. napi and P. melete larvae (nonhost). The wasp showed a shorter response to mechanical damage and damage made by Plutella xylostella or A thalia infumata larvae. This suggests the chemical information used by C. glomerata might be genus Pieris specific, but not host specific. The function of the chemicals is discussed in a tritrophic context.

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The behavior of female Exorista japonica Townsend (Diptera : Tachinidae) in response to an herbivore-damaged plant was examined in a wind tunnel bioassay. We used the common armyworm, Mythimna ( =Pseudaletia) separata Walker, as a host for this fly and as an herbivore to damage corn plants. Experienced flies conditioned to oviposit on the host/corn plant complex were attracted mostly to the host/plant complex and required a relatively short time to arrive at the plant. Damaged corn plants without host larvae and their frass were also attractive. However, only a few experienced flies were attracted to the undamaged plants. These two responses indicate that the damaged corn plants without the herbivore present emit an attenuated signal odor for female flies. The host larvae per se did not attract the flies. Naive flies had lower responses to the host/plant complex than the oviposition-experienced flies, indicating the importance of oviposition to the host with or without a damaged plant.

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Field observations and an experiment were conducted to clarify the seasonal cycle of Alydus calcaratus (Heteroptera : Alydidae) in the forest-steppe zone of Russia and to test the role of day length in the control of seasonal development of this species. Insects were reared under a constant photoperiod and at natural temperature. Two alternative photoperiodic regimes were used : short (14L-10D) and long (18L-6D) days. No significant differences in duration of nymphal development were observed between these conditions. Females laid eggs under both photoperiods, although preoviposition period was significantly shorter under long-day (11.6±1.4 days) than under short-day (13.8±1.5 days) conditions. Eggs were kept under the same photoperiodic conditions at a constant temperature of 24°C for two months. In the long-day regime, nymphs from 37.4% of eggs hatched on 14.1±1.3 days after oviposition (hatchability in the egg samples laid by one female varied between zero and 85.7%). During the same period, no nymphs hatched from the eggs laid and maintained under short-day conditions. These observations suggested that day length plays a principal role in diapause induction in this species.

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Diapause induction and termination in larvae of a phytophagous lady beetle, Epilachna admirabilis Crotch, were studied in the laboratory. The critical photoperiod was approximately 14.7 h. In photoperiodic transfer experiments between long, and short-daylengths at 24°C to estimate the beginning and end of diapause sensitivity, we estimated the time required for 50% diapause by probit analysis to be 2.1 days. The sensitive period began 6.3 days and ended 12.0 days after molting of 4th-stadium larvae. As their pupation starts mostly from 12 days after the 4th-stadium molt under conditions averting diapause caused by long daylength, larvae of this species are sensitive, and diapause ensues during a later stage of the 4th stadium. In relation to diapause termination, pupation was accelerated with increasing duration of cold storage (5°C). Larval diapause terminated without cold exposure in 33.2 days under long daylength and 90.6 days under short daylength. These results suggest that diapause termination and post diapause development are related to temperature, duration of cold storage, and photoperiod as a token stimulus.

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The protective role of uric acid against photooxidative stress was examined using the silkworm, Bombyx mori. The production of uric acid in the larvae was artificially reduced by feeding allopurinol, an inhibitor of uric acid synthesis. In the uric acid-deficient group, the average survival period under UV irradiation was shortened to 74% that of the non-treated group. The uric acid-deficient group was also hypersusceptible to the phototoxicity induced by rose bengal, and the average survival period was reduced to 52% that of the control group. These results proved that uric acid is effective in conferring protection against photooxidative stress in the silkworm.

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The numbers of nymphs and adults of the peach silver mite, Aculus fockeui, consumed by females of the two phytoseiid mites, Amblyseius sojaensis and A. eharai, were 9.2 and 13.3, respectively, when feeding was observed for 10 min. Functional responses of the two phytoseiid mites to the density of A. fockeui showed saturation curves, in which the maximum number of A. fockeui consumed per female per day was estimated to be ca. 300 and 400 for A. sojaensis and A. eharai, respectively. Thus, the two phytoseiid mites had great abilities to prey on A. fockeui, although the ability of A. sojaensis was somewhat inferior to that of A. eharai.

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Natural enemies of Thrips palmi were surveyed on Okinawa and Ishigaki Islands of the Ryukyu Islands, to identify potentially effective, indigenous natural enemies against this adventive pest. A number of predators were found : Piocoris varius. Orius tantillus and O. strigicollis were collected on Okinawa Island, while P. varius. O. tantillus and Campylomma chinensis were collected on Ishigaki Island. Of these indigenous predators, P. varius is most likely to be effective against T. palmi in wax gourd gardens on Okinawa Island. Outbreaks of T. palmi were found just after its accidental introduction into the Ryukyu Islands in 1980, but there have been no serious outbreaks on the islands since several years after the introduction. Our study indicates that the indigenous complex of natural enemies may play a key role in suppressing T. palmi populations in southern Japan. Potential use of the generalist predators on the Ryukyu Islands for the biological control of greenhouse pests under short-day conditions in more northern temperate regions is also suggested.

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We have developed a simple rearing system for Thrips setosus to facilitate the collection and maintenance of a large number of even-aged for use in transmission experiments of tomato spotted wilt tospovirus. The system was established using a leaf cage. The leaf cage consisted of an excised leaf of the plant Vigna sus-quipedaris, sandwiched between two acrylic plastic plates held by rubber bands. The upper plate had a 25 mm-diameter hole in the center and two air ventilation holes, while the lower plate was fiat. In this cage, approximately 75% of the total egg number could be collected during the first 6 h of a 24 h oviposition pe-riod, indicating that the first 6 h of the oviposition period is practical to collect eggs efficiently using this method. On day 6 after egg oviposition, 54.4% of the total number of hatched larvae was observed in the former half of the photophase (within 8 h after onset of the photophase), suggesting that this period is efficient for collection of larvae with synchronized age. This method was useful not only to collect a lot of synchro-nously hatched first instar larvae, but also to maintain them until adulthood without escape from the cage.

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An auto-infection system consisting of a modified sex pheromone trap and a bottle with exit holes containing conidia of the fungus Beauveria bassiana (9.3×10¹⁰/1g medium) was designed and tested to control the sweet potato weevil, Cylas formicarius (Fabricius) (SPW). Male weevils were attracted to the system by the phero-mone and exited the bottle after infection. In the sweet potato field where the systems were placed, the highest mortality of males by the disease was 96.2% on 21 days after treatment and that of females was 33.0% on 49 days. Rates of fungus carrier were 57.9% in males and 31.6% in females. In the treated field, the sex ratio of the SPW population was greatly skewed to females. Females seemed to be infected through mating with fungus carrier males. The advantages of this system are : 1) Attracted males are efficiently auto-infected with the fungus ; 2) only SPW is infected by this system ; 3) the fungus is easy to mass-produce ; 4) the cost of this system is low as compared with conventional field sprays ; 5) once attracted and infected, males can be expected to return to their habitat, which accelerates dispersal of the fungus.

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Four different NPV isolates from Autographa californica (AcNPV), Bombyx mori (BmNPV), Hyphantria cunea (HcNPV) and Spodoptera exigua (SeNPV) were characterized for their biological properties in four lepidopteran cell lines which were derived from S. frugiperda (IPLB-Sf-21), B. mori (BmN-4), Spilosoma imparilis (FRI-Splm-1229), and S. exigua (Se301). On the basis of the data on viral DNA replication, viral structural protein synthesis, budded virion (BV) yield, polyhedrin synthesis, and polyhedral formation in the infected cells, it was demonstrated that each of these NPV isolates established specific interactions with the respective cell lines. Of 16 NPV-cell systems examined, three NPV-cell systems exhibited two different types of abortive infection. In HcNPV-infected BmN-4 cells, viral DNA replication occurred but the infection aborted at the step prior to late gene expression, whereas both AcNPV-infected BmN-4 cells and HcNPV-infected IPLB-Sf-21 cells yielded BVs into culture medium but were defective in polyhedrin expression. In addition, it was found that SeNPV exhibited a unique infection process in FRI-SpIm-1229 cell cultures, in which viral DNA replicated and a limited number of polyhedra were formed in a restricted number of infected cells while few, if any, progeny BVs were produced and a significant proportion of infected cells displayed apoptotic-like morphology. The present study, thus, developed various NPV-cell systems which facilitate the analysis of molecular mechanisms underlying baculovirus host specificity determination.

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The effects of the timing and dose of entomopoxvirus infection in Pseudaletia separata larvae on the devel-opment of a braconid larval parasitoid, Cotesia kariyai, were studied under laboratory conditions. The infection of larvae with an entomopoxvirus (PsEPV) was deleterious to the development and subsequent survival of C. kariyai. The survival and development of C. kariyai in PsEPV-infected P. separata larvae depended on the viral dose, timing of viral infection and the length of time between parasitization and viral infection. The percentage of hosts with emergence of C. kariyai decreased with increases in PsEPV concentration and in-creased with progressive inoculation stages of larvae. No parasitoid larvae emerged from PsEPV-infected hosts when host larvae were exposed simultaneously to parasitization and inoculation of lethal dose of PsEPV. Survival of C. kariyai in PsEPV-infected hosts increased as the time between parasitization and subsequent viral exposure was increased. The body length of parasitoid larvae developing in PsEPV-infected hosts de-creased as the inoculation dose of PsEPV was increased. Parasitized larvae were more susceptible to PsEPV than nonparasitized larvae, regardless of the timing of parasitization and viral inoculation.

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Development of organophosphate and carbamate resistance was monitored by assaying the acetyl-cholinesterase (AChE) phenotype of individual green rice leafhoppers (Nephotettix cincticeps Uhler) of five strains which showed different levels of resistance to N-methyl carbamates. By applying this method to screening of various combinations of negatively correlated inhibitors, we observed that monocrotophos was negatively correlated to N-methyl carbamates in potency of AChE inhibition.

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Changes in the population densities of the peach silver mite, Aculus fockeui, with applications of a synthetic pyrethroid fluvalinate in peach orchards were examined. The injury level of leaves at harvest caused by A . fockeui was significantly higher in trees with an application of fiuvalinate in early July than in those with no applications. Fluvalinate had no effect on A . fockeui, but was extremely harmful to the phytoseiid mite, Amblyseius eharai, which was frequently observed in untreated trees. Population densities of two species of phytoseiid mites, A. sojaensis and A . eharai, were high from June to August in a peach orchard with no applications of fluvalinate, whereas phytoseiid mites did not occur until early September in a peach orchard where fluvalinate had been sprayed 6 times from late April to early July. This resulted in the peak density of A. fockeui reaching ca. 3 times the size of that in the former orchard. These results indicate that a marked resurgence of A. fockeui would occur because of the exclusion of phytoseiid mites when synthetic pyrethroids, which have no effect on A . fockeui and are harmful to the predators, are sprayed.

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Binomial sequential classification sampling plans were developed for use in classifying populations of Thrips palmi Karny, below or above a mean intervention threshold density (m_IT) for management decision making on the fall potato on Cheju Island, Korea. The proportion of potato leaves with at least T (tally threshold) thrips (P_T) was related to mean thrips density (m) with an empirical model In(-1n(1-P_T))=γ+δln(m). The P_T-m relationship fit the data well for T values of 1-10, with T=3 having the best fit. Wald's sequential probability ratio test was used to formulate sequential sampling stop lines relative to m_lT values of 5 and 10 thrips per potato leaf with a series of T. The sampling plans were evaluated using the operating characteristic and average sample number functions. Simulation analysis indicated that a binomial model with T=3 was best, and less than 60 samples, on average, were needed to classify populations relative to either m_IT value. The binomial sequential sampling plan was tested with sequential resampling simulation using 8 independent data sets for the validation. The binomial sequential classification sampling plans presented here should enhance the efficiency of pest management programs based on the prescriptive suppression of T. palmi on fall potato.

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The efficacy of four kinds of oils, neem, castor, sunflower and sesame, was evaluated for the control of infestation of stored azuki bean with Callosobruchus chinensis. Neem and sesame oil-treated beans were less preferred and oviposition of adults on these beans decreased. After three days of release, 100% adults were found dead on neem oil-treated beans and very few eggs were laid. Effects on the survival rate of immature beetles and percentage of seed weight loss were also recorded. Neem and sesame oils completely inhibited adult emergence and appeared to be most promising as a seed protectant against C. chinensis. The oil-specific activity and delay in larval development in oil-treated beans suggest that the protective properties involved chemical rather than physical factors.

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Reproductive incompatibility is known to occur in Tetranychus kanzawai. K strain females were found to be incompatible with T strain males, i.e., a cross between K strain females and T strain males resulted in only male progeny, whereas the reciprocal cross resulted in a higher egg hatchability but in a reduced sex ratio. To determine whether T. kanzawai populations collected from different localities belonged to either the T strain or the K strain, 74 local populations were tested. Of these populations, eleven belonged to the K strain and the others belonged to the T strain. Wolbachia infection occurred in local populations belonging to both the T and K strains. As all of the infected populations harbored a Wolbachia strain which does not influence compatibility of the host, Wolbachia is not responsible for the incompatibility between the T and K strains. Host plant specificity varied among local populations. Some populations successfully matured on tea, some attained maturity on hydrangea, and some were unable to develop on either tea or hydrangea. Thus, a wide range of genetic divergence was observed in T. kanzawai.

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