Growth-blocking peptide (GBP) was first identified in the hemolymph of the host armyworm, Pseudaletia separata, whose growth is halted in the last instar larval stage by parasitization with the parasitoid wasp, Cotesia kariyai. Studies on the mechanism of growth retardation by GBP revealed that GBP titers in hemolymph fluctuate synchronously with dopamine levels: GBP and dopamine peaks coincide with each larval molt period, during which larvae temporarily cease moving and feeding. The fact that GBP induced the elevation of dopamine concentration in the hemolymph was demonstrated in armyworm larvae by GBP injection. Dopamine elevation was also observed in insects exposed to various stress conditions such as parasitization and chilling. These results, together with the fact that dopamine itself inhibits larval growth, indicate that GBP induces growth retardation via the elevation of dopamine levels. Further, we demonstrated that the diapause-inducing influence of short day length also elevates dopamine concentrations in hemolymphs and the brain-central nervous system (Br-CNS) of the cabbage armyworm, Mamestra brassicae. The elevation of dopamine levels contributes to the onset of pupal diapause. We therefore proposed that a GBP-dopamine system contributes to the control of growth rates in insects. Recent studies by ourselves and other laboratories have found more than 10 homologous peptides in various insect species. These peptides have diverse functions: larval growth retardation, paralysis induction, cell proliferation, immune cell stimulation and cardioacceleration. As demonstrated, GBP itself exerts most of these functions, so it is reasonable to conclude that GBP and GBP-like peptides widely present in insects should be regarded as insect cytokines with a variety of functions.

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Developmental responses of an indigenous aphid parasitoid, Aphidius gifuensis were compared when incubated at a low or high temperature and a short or long day length. Host aphid mummification and parasitoid emergence from mummies were observed with very high probabilities of over 80% and 90%, respectively, at all treatments. Sex ratios of emerged parasitoids remained constant at approximately 0.6. Developmental periods of parasitoid progenies reared with a short day length were approximately equal to those with a long day length for both sexes, although the duration from mummy to emergence at 15°C significantly differed between short and long day lengths. These results were summarized as A. gifuensis complete development under low temperature and short day length conditions of 15°C and 10L-14D instead of entering larval diapause as mummies. We thus conclude that A. gifuensis populations introduced into domestic greenhouses can increase and work effectively as biological control agents against pest aphids even during the hibernal season with low temperature and short day length conditions.

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Adult burying beetles use the carcasses of small vertebrates for food and breeding their young. Some species are known to have optimum carcass sizes related to their body sizes, but their carcass use is difficult to observe in situ. We explored their size-related niche differentiation in carcass resource using stable isotope analysis. The largest Nicrophorus species in Japan (N. concolor) showed the highest δ¹⁵N, and the smallest Nicrophorus species in Japan (N. montivagus) showed the lowest δ¹³C and δ¹⁵N among all Nicrophorus species, suggesting that their niches are differentiated from those of other species in carcass resource. We also revealed a positive correlation between δ¹⁵N and body size. Ptomascopus morio showed significantly higher δ¹⁵N than all studied Nicrophorus species. This species does not show parental care behavior and the adults may feed on quite different resources from Nicrophorus species.

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Four microsatellite loci were isolated and characterized from the rice stem borer moth Chilo suppressalis, which is an important insect pest of rice plants in Japan. These loci were not in linkage disequilibrium; however, in two of four loci, the observed heterozygosities were significantly less than expected, possibly due to the effect of null alleles. Although caution should be taken in analysis, these loci were sufficiently polymorphic to be used for population genetic analysis of this species.

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We investigated the effect of the presence of an oviposition substrate on female remating behavior in three strains of the adzuki bean beetle, Callosobruchus chinensis. In the two strains with low levels of female remating, females maintained with an oviposition substrate, and thus allowed to lay eggs, had a greater tendency to remate than females maintained without an oviposition substrate to prevent them from laying eggs. The oviposition substrate had no significant effect on female remating in the strain with a high level of female remating. The results indicate that female remating is influenced by the presence of an oviposition substrate, an environmental factor, in C. chinensis. This suggests that females adaptively change their receptivity to remate in response to environmental factors affecting the costs and benefits of remating in C. chinensis.

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The developmental and reproductive characteristics of a mealybug, Phenacoccus solani, were investigated at 20, 25, and 30°C and a photoperiod of 16L : 8D. The total developmental periods of the immature stages and the pre-reproductive period of adults decreased significantly with increased temperatures. Survival rates of immature stages were high at all temperatures. The number of offspring produced per female was significantly lower at 30°C than at other temperatures. Adults lived significantly longer at 20°C than at other temperatures. Generation time was longest at 20°C. The net reproductive rate and the intrinsic rate of natural increase were highest at 25°C.

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To screen effective Trichogramma species or strains and to characterize their parasitism against Helicoverpa assulta eggs, parasitism by T. dendrolimi and T. chilonis was compared in glass tube and cage tests, and the effects of host egg age and location, and plant species were investigated. In the glass tube test, HJS and YYS strains of T. dendrolimi, and JDM and GGM strains of T. chilonis parasitized 72.2–97.6% of host eggs. In the mesh cage test, the JDM strain parasitized the highest (60.1±24.9%) and the GGM strain, the lowest (39.4±28.6%) level of host eggs. Host egg age showed significant influence on parasitism, and HJS, YYS and JDM strains all preferred 0–12 h to 12–36 h host eggs. The wasps parasitized significantly more host eggs on lower than on upper and bottom leaves, and a higher proportion of host eggs on the leaf upper side than on the lower side regardless of plant height, which contrasted to egg deposition by H. assulta. On pepper plants, parasitism by T. dendrolimi and T. chilonis was 31.1±13.9% and 32.8±10.2%, respectively, while on tobacco plants, it was 10.6±4.6% and 1.1±0.8%, respectively. The implications of these results are discussed with reference to inundative release.

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The rice stem borer, Chilo suppressalis (Walker) is an important lepidopteran pest of rice plants in Japan, and feeds on both rice (Oryza sativa) and water-oats (Zizania latifolia). We evaluated the difference in mating time of the two feeders under both laboratory and field conditions. The male moth of the water-oat feeders (WF) began to mate 7 h after the beginning of the scotophase, about 4 h later than the peak of mating of the rice feeders (RF). In accordance with this result, the body size of males trapped using synthetic sex pheromones differed between the two trap periods (sunset to 1:00 am vs. 1:00 am to sunrise) in the field, suggesting that the rice feeders were trapped earlier than the water-oat feeders. However, there was no unequivocal evidence showing limited gene flow between the two feeders at the level of allozyme polymorphisms. These results suggest that as the two feeders of C. suppressalis have recently diverged, the allozyme loci have not yet diverged to fixation.

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Outbreaks of Aulacorthum solani occurred on soybean in Miyagi and Yamagata Prefectures, northern Honshu, extensively in 2000 and 2001, and locally in 2003 and 2004. On the other hand, such an outbreak of A. solani has never been observed in Hokkaido Prefecture. To estimate whether genotypic composition are implicated in the outbreaks on soybean, we examined the esterase patterns detected by electrophoresis of 284 clones collected in these three prefectures and five other prefectures. We also examined the susceptibility to insecticides and life-cycle category of some of them. The esterase phenotypic composition was different between Hokkaido and Miyagi/Yamagata. This was especially so in the phenotypes at the presumed esterase locus 2. In Miyagi and Yamagata the phenotypes with band F and activity (++) were frequently found, but the phenotypes with activity (±) and (−) were not found. In Hokkaido the phenotypes with activity (±) and (−) were frequently found, but the phenotypes with band F and activity (++) were not found. Any of the esterase alleles at this locus were not associated with resistance to acephate or fenvalerate. Populations in Hokkaido and northern Honshu were holocyclic and consisted of various esterase forms. These results were discussed in relation to the outbreaks on soybean.

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Laboratory bioassays were conducted to evaluate the effect of pollens from insecticidal transgenic Bt corn (event MON863) expressing Cry3Bb1 endotoxin on two native non-target herbivorous beetles, Epilachna vigintioctopunctata (Coccinellidae) and Galerucella vittaticollis (Chrysomelidae) larvae. Larvae were reared on leaf discs exposed to corn pollen for 10 days after hatching. G. vittaticollis had no adverse performance in terms of larval survival and development (proportion of larvae to third instar) between pollen doses of 500 and 2,000 grains/cm². Similarly, E. vigintioctopunctata did not show significant deleterious effects between pollen doses of 250 and 2,000 grains/cm². From the actual pollen doses deposited on leaf surfaces near cornfields, it was concluded that corn pollen from MON863 has no adverse effects on E. vigintioctopunctata and G. vittaticollis populations living on wild plants near cornfields.

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Entomopathogenic fungal conidia are detached from the host cuticle by several environmental factors. Larvae of the scarab grub, Anomala cuprea, inhabit the soil, and are constantly in contact with the soil. The larvae were treated with imidacloprid to suppress the mobility, and then treated with fluorescein isothiocyanate labelled conidia of the entomopathogenic fungus, Beauveria amorpha. In the case of non-paralyzed larvae without imidacloprid treatment, conidia on the vertex, dorsum and abdomen became detached by 12 h after application. In contrast, the number of conidia on paralyzed larvae with imidacloprid treatment remained stable throughout the test period. In parallel with conidial detachment from non-paralyzed larvae, the number of conidia detected in the rearing soil increased. These results indicated that the fungal conidia adhering to the surface of scarab grubs are detached by friction with soil in association with the larval movement, suggesting that insect movement may be an important factor that affects the infection with pathogens.

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The relationship between the seasonal prevalence of the predacious coccinellid Pseudoscymnus hareja and the mulberry scale Pseudaulacaspis pentagona in tea fields was investigated using sticky traps set inside tea bushes. Crawlers (newly-hatched larvae) and winged adult males of P. pentagona and adults of P. hareja were captured in large numbers. The number of trapped P. hareja adults reached a peak 0 to 15 days (average: 6.9 days) after the peak in the number of P. pentagona crawlers in each tea field. P. hareja adults captured in this period are considered to have visited tea fields to prey on P. pentagona larvae and to deposit their offspring (larvae), which primarily consume P. pentagona larvae. Another relatively lower peak in P. hareja adults was found 0 to 14 days (average: 6.6 days) after the peak in the number of P. pentagona adult males. P. hareja adults trapped in this period are suggested to be those that had spent their larval period feeding on P. pentagona larvae and male pupae in tea fields. Thus, the seasonal occurrence of P. hareja adults in tea fields is associated with that of P. pentagona larvae as the main prey of P. hareja larvae.

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We investigated factors influencing the survival of the apple snail, Pomacea canaliculata during dormancy in the laboratory at 20–26°C. We placed snails of three size classes in small pots with soil and water, drained the water to induce self-burial, and subsequently checked the snails' survival at intervals. The duration of the dormant period, body size and the success of self-burial all affected the survival of the snails. The effects of water conditions (dry or moist) affected the survival of the snails through interactions with body size and duration. The longest duration of survival under dry conditions was 11 months, and a small proportion of medium-sized and large snails survived the entire experimental period of 29 months under moist conditions.

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In order to develop an artificial habitat encouraging the colonization efficiency of phytoseiid mites on fruit trees, we conducted choice experiments with a predacious phytoseiid mite, Neoseiulus californicus, using 22 types of artificial microstructures (3 cm×3 cm, less than 1 cm thick) in the laboratory. Large numbers of N. californicus preferred fine-textured urethane foam and a shading net, although the locations where N. californicus settled on each microstructure were different: more than 80% of N. californicus adults preferred being ‘on a plastic board under fine-textured urethane foam’, while more than 95% preferred being ‘on and in the shading net itself’. With respect to their practical use on fruit trees, shading nets are useful, because their size and thickness can be changed easily and they are also effective tools to transfer phytoseiid mites to trees with low phytoseiid densities. Thus, shading nets were considered to be the best candidate for an artificial habitat of phytoseiid mites on fruit trees.

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Resistance to fenvalerate was examined in a laboratory-selected population of the diamondback moth, Plutella xylostella, during exposure through 10 generations. Selection results showed that LD₅₀ values rose from 0.003 μg per larva to 31.1 μg per larva and 36.7 μg per larva respectively, in replications 1 and 2 during those 10 generations. Resistant line moth eggs were significantly smaller than those of moths before selection. Therefore, we selected a subpopulation of resistant lines under harsh environmental conditions of low humidity and high temperature, over 10 generations (Harsh line) without insecticide exposure. We selected another subpopulation of resistant lines under optimal environmental conditions of high humidity and normal temperature through all 10 generations (Optimal line). After 10 generations, the LD₅₀ of fenvalerate decreased to 0.03 μg per larva and 0.02 μg per larva under harsh conditions and 0.2 μg per larva and 0.29 μg per larva under optimal conditions. The LD₅₀ values were lower for the Harsh lines than for the Optimal lines in all generations. The egg size of both lines increased gradually through 10 generations. Comparisons of these two lines showed that the egg size increased more rapidly in the Harsh lines than in Optimal lines in early (first-sixth) generations. In subsequent generations, egg sizes were nearly normal in both lines. Comparison of immature survivability of Harsh and Optimal lines reared under those conditions showed that the survivability of Harsh line individuals was significantly lower than for Optimal lines. Comparison of the two lines' survivability showed an opposite result from the comparison when they were reared under equivalent optimal conditions. These results suggest that susceptibility to insecticides might recover more quickly in Harsh lines than in Optimal lines because resistant insects with small eggs had lower survivability than susceptible insects with normal eggs. They were eliminated more rapidly under harsh environmental conditions.

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A blue-green (BG) strain was established from a laboratory colony of Plautia crossota stali. This strain was characterized by a unique blue-green body colouration and pale green egg colouration with grey forewings, compound eyes and ocelli. The testicular epithelium for male adults was whitish in contrast to the orange-yellow colour for normal males. Reciprocal crosses between normal and BG strains indicated that the traits specific to the BG strain were recessive against normal phenotype and controlled by a single Mendelian unit. Double mating experiments in which BG females were mated with a normal and a BG male in this or the other order suggested that the sperm of BG males were as competitive as those of normal males. It was also found that the sperm of two males were mixed throughly soon after the second mating, although the precedence of sperm from a second male varied greatly for each female adult. The BG strain may be used as a genetic marker for behavioural, ecological and genetic studies in P. c. stali.

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The oviposition behavior of the gregarious tachinid fly, Bessa parallela (Meigen), on Pryeria sinica Moore larvae was studied in a wooded area in Fukuoka, Japan, to increase our knowledge of tachinid behavior in the field. Most B. parallela females were observed to approach or oviposit on P. sinica larvae on the ground, while in contrast only one female was found on a tree and did not oviposit. When hosts on the ground and trees were collected and examined, the number of hosts bearing tachinid eggs was significantly larger for hosts collected on the ground than on trees. When the parasitized hosts collected in the field were reared in the laboratory, the survival rates of B. parallela were not significantly different between hosts collected on the ground and those on trees. In the field, B. parallela females deposited more eggs on the head and thorax of P. sinica larvae than on other body parts.

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Cuticular hydrocarbons of Formica japonica mainly consisted of pairs of n-alkanes and alkenes from C23 to C33, but those of F. truncorum consisted of alkadienes, alkenes, n-alkanes, and methyl alkanes from C25 to C48, with relative ratios of 0.3%, 8.2%, 28.4%, and 63.2%, respectively. Very long-chained hydrocarbons, larger than C34, accounted for 55.6% of the whole hydrocarbons. Such hydrocarbons were not previously found, presumably because of differences in analytical methods. Even after these very long-chained hydrocarbons were added to the analysis, the hydrocarbon profiles remained similar among colony members, but different enough between colonies to allow identification.

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The seasonal prevalence of the citrus red mite and its predators on Satsuma mandarin trees was surveyed by naked-eye observation and the beating method in three commercial groves in Shizuoka Prefecture in 2003 and 2004. Of the predators, only phytoseiid mites were caught mainly by beating, and their population dynamics were synchronized with those of the citrus red mite from June to September. Most adult females of phytoseiid mites caught by beating belonged to the species Neoseiulus californicus. Furthermore, one population of N. californicus caught from a surveyed grove showed development and oviposition on the eggs of the citrus red mite as well as the Tetranychus urticae eggs under experimental conditions. These results indicate that an indigenous population of N. californicus in conventionally controlled citrus groves in central Japan has the ability to suppress the population of P. citri on Satsuma mandarin.

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Larval survival and development of Carposina sasakii were examined in apple fruits. Irrespective of the oviposition date between early June and late August, larval survival in apple fruits was low (0–20.8%). The duration from oviposition to larval emergence from the fruits varied greatly from about 30 d to more than 100 d. When eggs were laid after late June, some larvae remained in the fruits until harvest in late October or early November. The larval survival rate differed significantly depending on whether the fruit was picked from the tree. The survival rate of larvae that entered “unpicked” fruits in early July was only 6.3%. However, 72.1% of larvae successfully emerged from fruits that were picked immediately after larval entry, although these fruits were maintained under the same field conditions as the “unpicked” fruits. Larval emergence from “picked” fruits was more synchronous than that from “unpicked” fruits. These results suggest that low survival and the retardation of larval development are caused by factor(s) related to fruit growth, which remains to be detected.

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