Laboratory tests were carried out in order to evaluate the insecticidal effect of the pyrethroids deltamethrin, beta cyfluthrin and alpha cypermethrin at the rates of 0.125 and 0.250 ppm, against the confused flour beetle Tribolium confusum on stored wheat. Therefore, clean untreated wheat was sprayed with these insecticides and stored for six months. During this period, four bioassays were carried out (32, 66, 101 and 171 days after insecticide application), in order to evaluate the residual efficacy of each pyrethroid. In each bioassay, pyrethroid-treated wheat was infested with T. confusum adults, and dead insects were counted after 24 h, 48 h and 7 d of exposure. In addition, in each bioassay, the progeny production was also examined. Mortality was notably higher after 7 d of exposure, as compared to 24 and 48 h counts. At the 7 d-exposure counts, beta cyfluthrin, at 0.250 ppm, was more effective as compared to the other treatments. This pyrethroid provided a satisfactory level of protection against T. confusum for a relatively long period, since the mortality 1 and 3.5 months after the treatment, was 98.6 and 88.7% at the rate of 0.250 ppm and 83.6 and 58.2% at the rate of 0.125 ppm, respectively. Similar mortality levels to the low rate of beta cyfluthrin were also recorded for the high rate of alpha cypermethrin (87.4 and 55.3%, respectively). Six months after the treatment, the efficacy of the high dose of beta cyfluthrin was 77.7%, while for the other treatments the respective figures were rather low (<48%). No progeny production was recorded on treated wheat, after the removal of the exposed adults, in any of the treatments. Finally, when adults that survived after a 7 d exposure interval on treated wheat were placed on untreated flour, progeny production was recorded only in the last two bioassays and only in the case of alpha cypermethrin.

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To clarify the reason for the recent dramatic outbreak of the leafminer, Chromatomyia horticola (Goureau), on the green pea in Japan, the insecticide susceptibility of two leafminer populations collected from grower's pea fields in Shizuoka and Kagoshima Prefectures was measured in a laboratory assay. Of the five insecticides registered for leafminer control on the pea, cartap was moderately effective, but phenthoate, malathion, permethrin and tralomethrin were less effective on larvae of the leafminer populations at their recommended dilutions. The leafminer population from Shizuoka was slightly less susceptible than the population from Kagoshima to all insecticides tested by LC₅₀ assay. Emamectin-benzoate, fipronil, spinosad, chlorfenapyr, cyromazine and isoxathion were very effective in controlling leafminer populations. The impact of insecticide applications on the leafminer and associated parasitoids in pea fields in Shizuoka Prefecture was also discussed. Of the four samples of pea shoots collected from three fields, two samples collected one month after insecticide application had very few leafminers and many parasitoids. However the sample taken immediately after insecticide application had a very large number of emerged adult leafminers, but few parasitoids. The results suggest that the recent large outbreak of C. horticola might have resulted from a combination of low susceptibility to insecticides in the species and the destruction of the parasitoid complex due to frequent insecticide applications.

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Insect larval hemocytes change their morphology and function during metamorphosis. However, the mechanisms driving the timing of these changes and the coordination with other premetamorphic events largely remain unclarified. With advancing stages of the beetle Xylotrechus pyrrhoderus prepupal development, the cell density of hemocytes decreased and adherent cells increased when the hemocytes were transferred into basal medium. The response of hemocytes from mature larvae before the prepupal stage to 20-hydroxyecdysone (20E) and juvenile hormone III (JH) was increased adhesion and morphological change; adherent cells accounted for 36.0% and 15.0% of cells in the 20E- and JH-supplemented media, respectively, but only 8.5% of cells in basal medium. Moreover, 60.2% and 53.0% of the adherent cells changed to spindle-shaped cells in 20E and JH treatment, respectively, in contrast with 8.1% in the control. The responses of hemocytes to 20E and JH were dose-dependent, showing stronger responses at concentrations of 10⁻⁶ M or more. The extended spindle-shaped cells with longer cytoplasmic extension increased to 30.9% in media supplemented with both 20E and JH, compared with 9.7% for 20E alone and 3.6% for JH alone, suggesting that these two hormones act synergistically. The JH-related compounds, all-trans retinoic acid and farnesol, had no effect. The spindle-shaped cells were also observed at the same level as 20E-treated cells in non-treated cells after the third day of the prepupa stage when ecdysteroid titer is presumably high. These results indicate that the hemocytes of X. pyrrhoderus larvae are responsive to both 20E and JH.

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As a part of a risk assessment of the non-target effect of the introduced green lacewing on native ecosystem, we performed a laboratory experiment to characterize the symmetry of the interspecific predation between the introduced green lacewing, Chrysoperla carnea and the native sibling species, C. nipponensis among different stages. The elder and larger larvae always ate the younger and smaller individuals, regardless of species. When the same instar and similar sized larvae were paired, almost equal predation rates between the two species was observed. Our results suggest that size was the most important factor to determine the symmetry of the interspecific predation between C. carnea and C. nipponensis. Populations of C. nipponensis will not be decreased by interspecific predation with C. carnea without extreme mass releases of C. carnea in a small arena.

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The sex pheromone components for mating disruption of the rice leaf bug Trigonotylus caelestialium were examined in both the laboratory and the field. A rearing cage test in the laboratory showed that the copulation rate of T. caelestialium adults in cages treated with a dispenser loaded with the synthetic sex pheromone, a mixture of n-hexyl n-hexanoate, (E)-2-hexenyl n-hexanoate, and n-octyl n-butyrate (100 : 40 : 3), was lower than that of bugs in untreated cages, and that populations of the next generation were also reduced. In small-scale field tests (9 dispensers loaded with 50 mg of the sex pheromone placed at 5 m intervals in a 10 m×10 m square area), the numbers of males captured by traps baited with a lure containing the three components of the sex pheromone were reduced to some degree by treatment with either n-hexyl n-hexanoate or (E)-2-hexenyl n-hexanoate alone, or a 100 : 40 mixture of these two components. Furthermore, male capture by traps baited with the lure were mostly reduced by treatment of the 3-component sex pheromone, and also those baited with 3 virgin females. In large-scale field tests (200 dispensers each containing 300 mg of the 3-component sex pheromone in an area of 10,000 m²), the population densities of T. caelestialium and the numbers of males captured by traps in the treated fields were lower than those in the untreated fields.

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The influence of color discrimination on female host location was investigated in Eurema hecabe (Lepidoptera: Pieridae). Mated females with no oviposition experience were presented with artificial plant models treated with the methanol extract of the host plant, Lespedeza cuneata (Fabaceae). When gray models of different intensity were presented to females, they landed and deposited eggs more frequently on the light gray model. However, when a yellow green model was presented to females with the gray, they landed and deposited eggs predominantly on the yellow green model. In the latter experiment, most females did not visit the gray models frequently, although one of the gray models had a similar intensity to that of the yellow green model. This result supports that E. hecabe distinguish the yellow green model by color.

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In 2000 and 2001, studies were carried out to evaluate the influence of predators on the cotton aphid, Aphis gossypii Glover (Homoptera: Aphididae), in Xinjiang Uygur Autonomous Region, China, where alfalfa was mainly planted as an intercrop with cotton. There were 25 species of predators observed from June to August; 16 species of predators were caught in both cotton and alfalfa. Predators were classified into five groups: predatory beetles, lacewings, predatory bugs, syrphid flies and spiders. The total number of predators in alfalfa was 2.45 times and 20% more than that in cotton in 2000 and 2001, respectively. In an alfalfa-cutting experiment, it was found that predators increased significantly faster in cotton bordering the alfalfa-cutting treatment than in the non-cut control, and the growth of the cotton aphid population was delayed in a cotton field adjacent to the treatment compared to that adjacent to the control. This indicates that alfalfa-cutting induces predator immigration into adjacent cotton fields and helps control cotton aphids. The impact of alfalfa cutting on predators and cotton aphids was evident for about 14 days.

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The development and reproduction of the braconid wasp, Lysiphlebus japonicus Ashmead, parasitizing either symbiotic or aposymbiotic aphids, were investigated. In order to obtain aposymbiotic aphids, the black bean aphid, Aphis craccivora Koch, was fed at birth with Vicia faba dipped in 200 μg/ml rifampicin. Transmission electron microscopy revealed that the intracellular symbiotic bacteria (Buchnera) began to degenerate 2 days after the antibiotic treatment. Bacteria-free aposymbiotic aphids exhibited a reduced growth rate, adult size and reproduction rate. The development and reproduction of the parasitoids were clearly affected by the rifampicin treatment of the aphid host. The larval size and the growth rate of the parasitoids were reduced, and the emergence rate and the body weight of the wasps decreased by 13% and 54%, respectively. The number of progeny produced by the wasps that emerged from aposymbiotic aphids decreased by 25%. Possible factors involved in the effects of aposymbiosis on the parasitoids are discussed.

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Host-use pattern for overwintering and reproduction of the ragweed beetle, Ophraella communa LeSage, was examined in Tsukuba, Japan. Many adults of both sexes were found overwintering inside the rolled parts of dead leaves of Xanthium canadense in November. These adults had already accumulated triacylglycerol as energy reserves, and were able to survive the winter and to reproduce in the spring. No eggs and larvae were found on X. canadense throughout the observation period, although overwintered adults were temporarily found in May. In contrast, reproduction occurs on Ambrosia artemisiifolia and A. trifida in late April. These results suggest that O. communa adults mainly use dead leaves of X. canadense as an overwintering shelter in Tsukuba, while they reproduce only on A. artemisiifolia and A. trifida in the spring. Such a seasonal migration between host plants may be important for the survival strategy.

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The contact and ingestion toxicities of selected agrochemicals applied at the standard field rate against adult females and pupae in host mummies of a native parasitoid Aphidius gifuensis were studied using several bioassays. Fresh residues of five insecticides (cartap, chlorfenapyr, emamectin benzoate, permethrin and imidacloprid) were found to be highly toxic against adult females as compared with the pupae in mummies. Evaluation of the residual effects of these five insecticides on cabbage foliage showed that cartap and imidacloprid were highly persistent. In the same assay, two IGRs (chlorfluazuron and lufenuron) and a fungicide (copper oxychloride) were harmless against adult females. When these agrochemicals were fed orally at the field rate, the mortality of adult females ranged from 13.3 to 46.7%. Ingestion of copper oxychloride had a slightly negative effect on parasitism.

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The reproductive capacity and host handling behavior of Gryon philippinense (Ashmead), an egg parasitoid of Acanthocoris sordidus Thunberg, were investigated under laboratory conditions. The reproductive capacity was studied at 25.0±1°C, LD 16 : 8. The highest daily average progeny production of the mated G. philippinense was recorded on the first and second days after emergence from the host eggs. The fecundity of 1-d and 2-d-old females of G. philippinense was 48.5% of the total fecundity. The estimated average survival rate of the immature stage of the female G. philippinense was 95.0%. The intrinsic rate of natural increase r_m was 0.174. The females of G. philippinense mostly deposited the male egg in the first host found. After every successful oviposition, the females of G. philippinense marked the parasitized egg.

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The among-tree differences in the inhibition of systemic dispersal of Bursaphelenchus xylophilus by Pinus densiflora were determined. Two-year-old branches were collected from four different aspects and at two different heights from six field grown P. densiflora. The virulent isolate of B. xylophilus, T-4, was inoculated on the upper end of 5-cm-long branch sections placed upright in a glass vial. The number of nematodes passing through the sections over 24 h was counted. Daily changes in the inhibition of systemic spread of the nematode were also determined. Two-year-old branches were collected at four hour intervals for 24 h from six additional trees. These branches were then inoculated with the nematode. The number of nematodes passing through the branch sections differed among the pine trees but did not differ between the branch heights or aspects. A diurnal change in the passing nematode number was observed only for a tree which grew on the top of a steep slope.

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Mating tests between Okinawa mass-reared and Taiwan wild strains of the melon fly, Bactrocera cucurbitae (Coquillett), were conducted in transparent acrylic plastic cages in the laboratory. The Okinawa mass-reared strain has been cultured for about 150 generations under artificial rearing conditions. The two strains of melon fly could mate with each other. Moreover, no significant assortative or disassortative mating was observed. Therefore, we suggest that the Okinawa mass-reared melon fly is compatible of mating with the Taiwan wild melon fly, at least under the laboratory conditions employed here.

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A multiple-nucleocapsid nucleopolyhedrovirus (MNPV), named Perina nuda MNPV (or PenuNPV), isolated from P. nuda (Fabricius) (Lepidoptera: Lymantriidae)—a major banyan pest—was studied in terms of its main morphological, biochemical, and biological properties. The pleiomorphic occlusion bodies were 1.7–5.4 μm in diameter with a mean size of 2.2±0.52 (μm±SE), and their most prominent protein had an apparent molecular mass of 32 kDa. The DNA genome size was estimated to be 120.38±0.38 (kbp±SE) based on restriction endonuclease fragment sizes. The median lethal dose response (LD₅₀) for this virus in 2nd to 5th instar P. nuda larvae were estimated at 154, 1,431, 14,458, and 169,137 occluded bodies per larva, respectively. In host range tests, other nine lepidopteran species from five families were not susceptible to PenuNPV. The high pathogenicity and specificity of this newly described MNPV indicate that it is indeed a good candidate for the biological control of this moth.

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Artificial laboratory selections for resistance and susceptibility to fenpyroximate were performed in a population of the two-spotted spider mite, Tetranychus urticae Koch (green-form), collected from a commercial strawberry field in the State of São Paulo, Brazil, in 1999. After five selections for resistance and three selections for susceptibility, the resistance ratios (R/S) at the LC₅₀ and LC₉₅ reached 2,910 and 2,280, respectively. Cross-resistance relationships between fenpyroximate and eight other acaricides were evaluated using the selected susceptible and resistant strains of T. urticae. The results indicate positive cross-resistance between fenpyroximate and acaricides, pyridaben and dimethoate. No cross-resistance was detected for acaricides, propargite, abamectin, milbemectin, fenpropathrin and cyhexatin. The studies on genetics of fenpyroximate resistance indicate that the fenpyroximate resistance is controlled by one major, incompletely dominant factor. Frequencies of fenpyroximate resistance decline significantly in the absence of selection pressure, under laboratory conditions, however, the rate of decline is not high.

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Captures of diamondback moth (DBM), Plutella xylostella (L.), with different lures and trap designs were assessed in Hanoi, Vietnam. The lures in plastic basin traps with water containing detergent (5‰) had the most captures. Both Chinese lures and Japanese lures could effectively attract DBM males from January to May in 2002. The effective period of Chinese lures and Japanese lures was 30 days, during which time the captures of the two types of lures were not significantly different. Mass trapping of DBM with Chinese lures in plastic basin traps and BT (Bacillus thuringiensis) applications in cabbage or kohlrabi fields could decrease the population densities of DBM.

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The effects of jasmonic acid (JA) and benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester (BTH), a functional analogue of salicylic acid, treatment of lima bean plants on the egg production were investigated in a herbivorous mite, Tetranychus urticae. JA and BTH were applied at three concentrations for each treatment to soil in pots containing plants. Only the 0.1 mM JA-treatment significantly reduced the number of eggs laid by T. urticae over a three day period, whereas higher (1 mM) and lower (0.01 mM) concentrations did not affect the egg production of T. urticae. Fewer eggs were laid by T. urticae on lima bean plants treated with 1 mM and 10 mM BTH than with 0.1 mM BTH. These data suggest that JA and BTH are involved in the direct defense of the lima bean plant against T. urticae.

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The effect of multiple parasitism of an endoparasitic wasp, Dacnusa sibirica, on several life history traits of two ectoparasitic wasps, Diglyphus isaea and Hemiptarsenus varicornis was examined. Two types of Liriomyza trifolii larvae were used as hosts. One type was a larva parasitized by D. sibirica and the other was a healthy one. Individuals of one of the two types of hosts were exposed to female adults of the two species of ectoparasitic wasps. The adult handling time was measured and the developmental period, mortality in nymphal stages, emerged sex ratio, and the length of hind tibia of newly emerged D. isaea and H. varicornis wasps were surveyed. We found the parasitization by D. sibirica had no effect on the life history traits of the two ectoparasitic wasps. Thus, we conclude that the two ectoparasitoids did not decrease the activity of parasitization under the existence of D. sibirica.

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The predatory abilities of Amphibolus venator (Klug) on the stored-product insect pest Tribolium confusum Jacquelin du Val were examined. A. venator adults (5–15 days old) were starved for 3 days and then introduced individually into plastic containers containing different prey densities (3, 5, 10, 15 or 20) of last-instar larvae, pupae or adults of T. confusum. The assay was carried out at 25°C and 30°C for 1 day. The number of T. confusum killed by A. venator during 10 days was also investigated a prey density of 10 individuals. A. venator attacked all stages tested: mature larvae, pupae and adults. A. venator targeted mature larvae preferentially to the other stages. The number of prey killed by A. venator increased at high prey density, and the functional response of A. venator exhibited Holling's Type II response for all the prey stages. Females tended to kill more prey than males. Predation by A. venator was more effective at 30°C than at 25°C.

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Seven species of the Bactrocera dorsalis complex, B. dorsalis, B. papayae, B. carambolae, B. philippinensis, B. occipitalis, B. caryeae and B. kandiensis, were found in a total of 1,093 specimens collected from 136 fruit samples carried by travelers from Asian countries and intercepted by the plant quarantine at Narita Airport of Japan from 1979 to 1998. Two sympatric species combinations, i.e., B. philippinensis vs. B. occipitalis and B. papayae vs. B. carambolae, were distinguished based on aculeus and aedeagal length. However, no difference in aculeus and aedeagal length was found between the other two sympatric species combinations, i.e., B. dorsalis vs. B. kandiensis and B. dorsalis vs. B. caryeae. A comparison of the detection frequency in each host fruit between the two sympatric species of the above two combinations suggests that B. papayae and B. carambolae have different host preferences while B. philippinensis and B. occipitalis have no differences in host preference.

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Two populations (Replications 1 and 2) were selected for 8 generations with fenvalerate at a LD₅₀ dose to compare the biotic performances and fitness of resistant and susceptible strains of the diamondback moth (DBM), Plutella xylostella. The LD₅₀ value rose gradually from 1.4×10⁻³ μg/larva to 6.7×10⁻² μg/larva in Replication 1 and to 4.9×10⁻² μg/larva in Replication 2. The resistance ratio was thus 67-fold and 49-fold respectively. The eggs of the selected strain were significantly smaller than those of the non-selected strain within 2 or 3 generations, then became stabilized in Replication 1 and fluctuated in Replication 2 at 1.20×10⁻² mm³. The size of the non-selected strain fluctuated around 1.35×10⁻² mm³ in both replications. To investigate the genetic changes in biotic performances of DBM in the selected strain, offspring of the selected and non-selected strains were individually reared at every other generation. The survival rate of immature stages, developmental period, pupal weight, adult longevity, fecundity of females and size of eggs laid by females were compared between the two strains. The survival rate of the selected strain was significantly lower than that of the non-selected strain in the 2nd generation. The survival rate of the selected strain also tended to be lower in the other generation. The fecundity of females of the selected strain tended to be higher than in the non-selected strain. The eggs of the selected strain were significantly smaller than those of the non-selected strain in all generations. The development period, pupal weight and longevity of adults did not significantly differ between the two strains in any generation. These results suggest that successive selection with fenvalerate at a sublethal LD₅₀ dose yielded a fitness disadvantage in the DBM population.

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Queen mating frequency, genetic relatedness between workers and worker reproduction were estimated in Vespa mandarinia by microsatellite DNA markers. Of 20 colonies examined, eighteen contained queens inseminated by a single male and two colonies contained queens inseminated by two males. The estimated effective number of matings was 1.03±0.023 (mean±SE) with 85% of the offspring of the two multiply-mated queens being sired by one of the two males. The genetic relatedness between workers was 0.738±0.008, which was almost identical to the predicted value of 0.75 under monogyny and monandry. For this low paternity, kin selection theory predicts a potential conflict between queens and workers over male production. To learn whether males are derived from queens or workers, 400 males from 20 colonies were genotyped at four microsatellite loci. We found that queens produced all males. This finding was confirmed by the observation that 4,317 dissected workers had not developed ovaries. There was no relationship between queen mating frequency and the frequency of worker reproduction, and workers did not produce any male offspring. These results strongly suggest that male production dominated by queens in V. mandarinia is possibly due to worker policing.

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