The attractive aggregation pheromone from males of the bean bug, Riptortus clavatus, has been identified as a blend of (E)-2-hexenyl (E)-2-hexenoate, (E)-2-hexenyl (Z)-3-hexenoate and tetradecyl isobutyrate (3 mix). When intact male bodies were extracted with hexane, octadecyl isobutyrate was detected in addition to the known 3 mix. Octadecyl isobutyrate was also detected in airborne volatiles using the glass-beaker collection method. In field experiments, the attractiveness of tetradecyl isobutyrate or 3 mix to R. clavatus was increased by the addition of octadecyl isobutyrate. These results suggest that octadecyl isobutyrate is one of the components of the attractive aggregation pheromone of R. clavatus, and may act as a synergistic composition in this bug.

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We propose a sampling method using a median (random-median sampling) for estimating the mean and variance of a normally distributed population. First, a sampling unit is selected at random, and then two sampling units adjacent to the selected sampling unit are drawn. These three units are compared and only the unit with the median quantity among the three units, which we call the local median, is adopted. This procedure is repeated for a given sample size. A computer simulation was conducted to compare the required sample size for random-median sampling with that for simple random sampling for homogeneous populations. The sample size required to attain a given precision of estimates by random-median sampling relative to that by random sampling (=100) was shown to be constant, i.e. about 45%, irrespective of the mean and standard deviation of the population; therefore, this principle is generally applicable for any normally distributed populations. The discrimination limit (DL) is defined as 10% of the mean of the population when considering practical field selection of the median by eye. Random-median sampling with a DL in which samples are randomly selected among candidates when the difference between three or two, candidates is smaller than the DL, also decreased the sample size significantly. The sample sizes required by random-median sampling were 45–60% of those required by simple random sampling when the DL ratio (=standard deviation of the population/DL) was greater than 1.5. Therefore, in field sampling, when selection of a median is not time-consuming, for example, when examining soybean yield, random-median sampling with a DL saves labor in comparison with random sampling, at least for homogeneous populations. Unbiased variances of samples from random-median sampling and random-median sampling with a DL were about 45% and 45–60% of those from random sampling, respectively. Thus, it is possible to estimate the variance of the population using both random-median methods.

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The ubiquitous generalist predator Andrallus spinidens (F.) is found in North Iran, which is dominantly cultivated with rice plants. Live and frozen larvae of Galleria mellonella L. and Ephestia kuehniella Zeller were offered to A. spinidens in order to assess their effects on reproductive performance. Predators consuming either live or frozen larvae of G. mellonella developed and weighed similarly, but those fed on live or frozen larvae of E. kuehniella had significantly different developmental times and body weights. Predators feeding on live larvae of E. kuehniella weighed more than those fed on corresponding frozen prey. The fecundity and longevity of the predator were affected neither by prey species nor by prey freezing; nevertheless, egg hatchability was mainly affected by prey freezing. Generally, the use of frozen larvae can be recommended when live prey are scarce.

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We studied the yield and biological activity of polyhedral occlusion bodies (POBs) in a Spodoptera litura multicapsid nucleopolyhedrovirus (SpltMNPV) harvested from larvae of S. litura on different days postexposure to the virus (dpe) by dosing fifth-stadium larvae with the virus. The yield of POBs in live larvae at 5 and 7 dpe was approximately 10 and 40%, respectively, compared to that from cadavers 8 dpe onward. A similar trend was observed in biological activity. POBs in live larvae at 5 dpe were less infectious than those harvested after larval death. The infectivity of POBs in live larvae at 7 dpe was intermediate, but comparable to that of POBs harvested after larval death. The volume of POBs was likely related to differences in biological activity. The volume of POBs harvested at 5 dpe was significantly smaller than that harvested 7 dpe, which was significantly smaller than that harvested after larval death. We discuss the results with respect to the mass production of SpltMNPV in S. litura larvae.

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To examine the effects of spider predation on pest populations in untilled paddy fields, we constructed life tables for immature stages of the migrant skipper Parnara guttata guttata Bremer et Grey artificially inoculated into untilled and tilled paddies in 2000 and 2001, and conducted a spider removal experiment in 2001. The life tables showed that the migrant skipper larval mortality rate was significantly higher in untilled than in tilled paddies. Unknown factors mainly contributed to this high mortality rate in untilled paddies. The spider removal experiment suggested that the presence of spiders was related to the high mortality rate of migrant skippers in untilled paddies.

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A storage protein gene, CsSP2, was cloned and sequenced from the rice stem borer, Chilo suppressalis. Analysis of the cDNA sequence revealed an open reading frame of 2,118 bp in length which encodes an arylphorin-like protein with a calculated molecular weight of 83.7 kDa. The expression level of CsSP2 was higher in non-diapausing larvae than in diapausing larvae at 20°C. When diapausing larvae were acclimatized in a stepwise fashion from 20°C to 5°C, CsSP2 expression was up-regulated five days after acclimation at 15°C. The level was maintained for 10 days after acclimation at 5°C and down-regulated thereafter. Some up-regulation in CsSP2 expression was detected in the post-diapause state. In non-diapausing larvae, CsSP2 expression was down-regulated in the course of cold acclimation. Protein products of CsSP2 might have an important role as an amino acid reservoir or a cellular defense mechanism during diapause.

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The growth rate and anticipated longevity of Chrysopa phyllochroma fed on Aphis gossypii were determined to test the two following hypotheses: a) When prey is quite sufficient, predators show the maximum growth rate; b) without prey provided, predators have a constant anticipated longevity. Considering assimilative efficiency (k), a new model was suggested: G=G₀[1−e^−k(I−C)]. Fitted to the new model, the maximum growth rate (G₀), respiration threshold (C) and assimilative efficiency of larvae (I) were 15.256, 0.529, and 17.624, respectively. There were significant linear correlations between the maximum growth rate and the development day-age of larvae (D), the respiration threshold and D, except between assimilative efficiency and D. Under the condition of no prey, stage mortality curves of larvae were fitted by Normal Distribution Curve. The anticipated longevity of larvae at 0.5, 1, 2, 3, 4, and 5 day-age was 29.56, 38.97, 46.79, 48.73, 53.15, and 59.77 h, respectively. There was a significant logarithmic correlation between the anticipated longevity of larvae and D. The accumulated weight loss of larvae increased as the survival time of larvae was prolonged, and there was a significant logarithmic correlation between the accumulated weight loss and survival time.

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We investigated the predatory ability of Carabus yaconinus (Coleoptera: Carabidae) on larvae of Spodoptera litura (Lepidoptera: Noctuidae) in the laboratory. A C. yaconinus adult preyed on ca. 90 S. litura larvae at the second-instar stage during 24 h. The number of larvae killed in 24 h decreased to ca. 40, 30 and 20 at third-, fourth- and fifth-instar stages, respectively. The wet weight of S. litura larvae killed by a C. yaconinus in 24 h increased with the larval stages of S. litura, and was highest for the fifth-instar stage. C. yaconinus adults occasionally left the predation unfinished and bit another live prey. The proportion of half-eaten prey varied with the larval stage of the prey. C. yaconinus can efficiently kill large numbers of S. litura larvae; thus, it may play an important role as a natural enemy of lepidopteran pests in agricultural fields.

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Effects of nucleopolyhedrovirus (NPV) on antibacterial peptide gene expression and peptide production in Bombyx mori larvae remain unclear. Antibacterial activity was first examined with the hemolymph from B. mori larvae infected with B. mori NPV (BmNPV) and injected with bacterial lipopolysaccharide (LPS) 72 h postinfection (p.i.). No antibacterial activity was detected. Expression of four antibacterial peptide genes were next analyzed in B. mori larvae infected with BmNPV. Although antibacterial peptide genes were activated upon injection of LPS in the larvae infected with BmNPV, none were triggered by BmNPV alone. Production of the antibacterial peptide cecropin B was next examined by Western blotting. Cecropin B was not detected from 72 to 96 h p.i. The absence of cecropin B was coincident with an increase in BmNPV cysteine proteinase (CP) activity. Cecropin B production was confirmed at 96 h p.i. in the larvae infected with CP-deficient BmNPV, indicating that the antibacterial peptides are degraded by BmNPV-CP at a very late stage of viral infection. These results suggest that BmNPV neither activates nor suppresses gene expression of antibacterial peptides and that absence of antibacterial activity is due to BmNPV-CP in B. mori larvae.

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The development, survivorship and reproduction of the whitefly Bemisia argentifolii Bellows et Perring (B. tabaci [Gennadius] B-biotype), raised on four commercial vegetables, were studied in the laboratory at 25°C. The development time of B. argentifolii was 21.8 d on eggplant, 22.4 d on cucumber, 22.7 d on sweet pepper and 25.6 d on tomato; the development time on tomato was significantly longer than that on the other vegetables. The survival of immature B. argentifolii raised on eggplant was significantly higher than on tomato. The mean lifetime fecundity of B. argentifolii on eggplant, cucumber, sweet pepper and tomato was 221.3, 167.6, 92.3 and 62.9 eggs, respectively; lifetime fecundity on eggplant was significantly greater than that on the other plants. The intrinsic rate of natural increase (r_m), net reproductive rate (R₀) and mean generation time (T) was 0.168, 185.1 and 31.2 d on eggplant; 0.153, 130.7 and 31.8 d on cucumber; 0.143, 73.1 and 30.0 d on sweet pepper; and 0.110, 36.1 and 32.7 d on tomato, respectively. Based on population growth parameters, we conclude that eggplant is the most suitable and tomato the least suitable host plant for B. argentifolii.

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The phylogenetic relationships among 16 species including 10 thrips vector species of tospoviruses were analysed using partial sequences of three genes: mitochondrial COI, nuclear 28S ribosomal DNA and the elongation factor-1α (EF-1α) in order to reveal the influence of lineage among thrips vector species on the vector competence of tospoviruses. The phylogenetic trees of thrips suggested that distinct clades were formed between the genera Frankliniella and Thrips including vector species at least in combined nuclear DNA data, although COI data showed a similar result despite low bootstrap value in the root of Thrips clade. Scirtothrips had an ambiguous phylogenetic position in this study. Vector and non-vector species were found within the same clade in the genus Thrips. Compared with the phylogenetic tree of thrips, the virus phylogeny inferred from the nucleocapsid (N) protein sequence were likely to correspond to the phylogeny of thrips, genera Frankliniella, Thrips and Scirtothrips, respectively, and also to the primary host plants under natural conditions. These results suggested that the vector competence of thrips for tospoviruses might be influenced by the lineages of thrips vectors as well as host plants.

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The feeding behavior of the rice bug Leptocorisa chinensis (Heteroptera: Alydidae) on the panicles of Oryza sativa rice was observed. The nymphs showed typical behavioral phases towards the rice panicles: antennation, extension of the rostrum, repeated dabbing with the labium, rostrum placing on the plant surface, stylet penetration and continuous sucking. The nymphs also showed similar behavioral phases except for continuous sucking on filter paper treated with a methanol extract of rice panicles. The frequency of bugs showing antennation and repeated dabbing was significantly higher on filter paper with the rice extract than on the control. These results suggest that there are chemical cues in rice panicles which stimulate behavior such as antennation and repeated dabbing by rice bugs.

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Genetic variations of the internal transcribed spacer-1 region in sweet potato weevil, Cylas formicarius, were examined from 27 collection sites in the main infested areas in the world, except Africa, in this study. The ITS-1 lengths of 36 weevils tested in this study ranged from 557 to 587 bp, and were conspicuously longer in weevils from India. The genetic distances between weevils from India and from the other areas tested were larger than among weevils from the latter areas. The phylogenetic tree based on ITS-1 sequences consisted of two main clades of India and East Asia consisting of Northeast Asia and Southeast Asia subclades. The former subclade was also divided into three minor subclades. Weevils from Georgia and Hawaii (USA), and St. Kitts (the West Indies) belonged to the same subclade as those from Guangdong (China) and Hanoi (Vietnam). Also, weevils from the Ogasawara Islands (Japan) belonged to the same subclade. On the other hand, weevils from the Southwest Islands (Japan) belonged to the same subclade as those from Taiwan. When referring to human historical events, C. formicarius would have gradually spread in southern Asia due to its limited dispersal ability since originating in the Indian subcontinent 90 million years ago. However, after becoming associated with sweet potato, especially after the nineteenth century, local populations with fairly different genetic properties from Indian weevils would have been rapidly spread by human transportation of infested sweet potato throughout the world.

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A population of green rice leafhopper, Nephotettix cincticeps Uhler (GRH), was artificially selected on 5 resistant rice varieties in the laboratory. The GRH lines selected on Saikai 164, Saikai 182, and Kanto-PL 6 were able to survive and reproduce on their respective varieties. In these lines, the developmental period of nymphs was shortened by continuous selection, although in the first generation it was longer than that of the line reared on Nipponbare carrying no resistance gene. We could not establish GRH lines virulent to Norin-PL 5 or Norin-PL 6. Six lines, reared on IR 24, Chugoku 105, Saikai 164, Saikai 182, Kanto-PL 6, and Aichi 80, were assessed for virulence among different resistant varieties by conducting a seedling test. All lines were highly virulent to the varieties on which they were selected. Similar virulence was obtained for combinations of IR 24 and Chugoku 105 lines, Saikai 164 and Saikai 182 lines, and Kanto-PL 6 and Aichi 80 lines. The Kanto-PL 6 and Aichi 80 lines were moderately virulent to Tadukan and Rantaj-emas 2. No lines were virulent to Norin-PL 5, Norin-PL 6, and Pe-bi-hun. The results of the leaf blade test were similar to those of the seedling test. The allele test confirmed that the GRH-resistance genes of Kanto-PL 6 and Aichi 80 are the same, and the resistance gene of Norin-PL 2 is located at a different locus from that of Kanto-PL 6 and Aichi 80. These results suggest that the virulence of GRH biotypes corresponds to the resistance genes of rice varieties and therefore, the use of biotypes allows the identification of groups of rice varieties that have similar resistance genes. We propose that the biotypes virulent to Grh 1-, Grh 2-, and Grh 3 (t)-carrying varieties be designated “Biotype 1”, “Biotype 2”, and “Biotype 3”, respectively.

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Midguts from Plutella xylostella, which are susceptible (PXS) and highly resistant (PXR) to Bacillus thuringiensis Cry1Ac, were homogenized and reacted with UDP-6-³H-galactose (Gal) or UDP-6-³H-N-acetylgalactosamine (GalNAc) in a bid to find a resistance mechanism. Gal was incorporated into both chloroform/methanol (C/M) soluble and insoluble fractions but GalNAc was incorporated into only the C/M insoluble fraction. PXS demonstrated a significantly higher level of incorporation; in particular, GalNAc was incorporated into the C/M insoluble fraction 1.5 times more in PXS than in PXR. The incorporation of Gal and GalNAc was enhanced with Mn²⁺ 2- and 4-fold, respectively. The tissue homogenate was fractionated after the incorporation of sugars and the cytosol fraction rich in microsome (Micro/Cyto) had the highest radioactivity. Although the incorporation of these two sugars was higher in PXS, the level of incorporation was at best 2-fold higher. Mutation in fundamental steps of oligosaccharide synthesis must be lethal, thus, the mutation must be strictly limited to that bringing the different sugar residue(s) to the outer region of the oligosaccharide. This must be the reason why the lower sugar transferase activity in PXR could not explain the substantially higher resistance in PXR. We briefly discuss the mechanism of resistance in P. xylostella against Cry1Ac.

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A Rutaceae-feeding swallowtail butterfly, Papilio protenor demetrius, exploits only a few plant species as hosts in the field. We examined in detail the acceptability of five potential rutaceous hosts occurring in the subtropics for ovipositing females of a Hiroshima population of the butterfly. The plants tested were Citrus depressa, Toddalia asiatica, Evodia meliifolia, Melicope triphylla, and Murraya paniculata, which are distributed mainly in the Southwestern Islands of Japan, thus in allopatry with the butterfly. Female responses to the foliage, methanol extracts and partitioned fractions from these plants were assayed for the presence of oviposition stimulants and/or deterrents. The foliage of C. depressa and T. asiatica strongly stimulated egg-laying, whereas ovipositing females only marginally accepted E. meliifolia and Me. triphylla, and virtually rejected Mu. paniculata. Further experiments with methanol extracts and fractions derived from the respective plants revealed that both C. depressa and T. asiatica contained potent oviposition stimulant(s) particularly in the aqueous fractions, and that the aqueous fractions of E. meliifolia and Mu. paniculata, despite their poor or little acceptability, contained moderate and weak stimulant(s), respectively. However, certain volatile deterrent(s) seemed to be responsible for the rejection of Mu. paniculata by females. Me. triphylla appeared to have neither appreciable stimulant(s) nor deterrent(s). Larval survival on these plants was also recorded as an estimate of fitness. Larvae performed very well on C. depressa. Unexpectedly, however, larvae did not survive on T. asiatica at all, but successfully grew on E. meliifolia. Larvae altogether failed to grow on both Me. triphylla and Mu. paniculata, suggesting the involvement of antifeedant(s) and/or toxic substance(s) in those plants to which larvae were maladapted.

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Laboratory kernel-kernel interaction experiments were carried out to assess the influence of mechanically damaged, insect-damaged, and intact maize kernels (conditioned or not) on the behavior of adult maize weevil, Sitophilus zeamais Motschulsky. S. zeamais adults were much more attracted to insect-damaged or conditioned insect-damaged kernels, than by the other two conditioned kernel categories considered. The intact kernels were more attractive than conditioned mechanically damaged kernels, but without significant difference. The “attractiveness” order of the kernel for S. zeamais adults was: insect damaged>intact>mechanically damaged. When fresh mechanically damaged and stored mechanically damaged kernels as well as fresh insect-damaged and stored insect-damaged kernels were compared, significant differences in the attraction of S. zeamais adults were noted.

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We propose a simple visualization method, Shared Loci Correspondence Analysis (SLCA), to reconstruct nest-mate patterns of bumble bees with co-dominant genetic marker data. The method begins with a similarity matrix based on pairwise comparison of allele-sharing patterns among individuals, which is then sorted using correspondence analysis. The resulting matrix represents visually estimated sibling groups along its diagonal. This method can be applied to all haplodiploid species to estimate full siblingship. In particular, SLCA does not require the estimation of allele frequency in a population. It is difficult to conduct large-scale sampling when studying wild populations, and hence we cannot accurately estimate allele frequency. Therefore, SLCA would solve various problems in estimating social structure, mating behavior, and the dispersal range of wild insect populations, for which the collection of large amounts of data is prohibitive. To illustrate our algorithm, we used two types of actual microsatellite data collected from wild populations of Bombus ardens and Bombus diversus. The result of the data sets shows that SLCA can accurately cluster nest mates.

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Females of the black chafer, Holotrichia loochooana loochooana emit anthranilic acid which attracts males and also induces female aggregation. Such aggregation comprises different groups of females: those settle first and began to release pheromone and the reinforcements that are attracted. To find out the female heterogeneity, it is essential to quantify the airborne pheromone released by individual females. Two methods were established for quantitative analysis of airborne pheromone, anthranilic acid from female individuals: Collection of released pheromone to glass beakers in the laboratory and collection into a portable device equipped with glass-bead in the field. Both approaches were followed with HPLC analyses. In the laboratory, large variations were found both in calling durations [19.4±18.8 min (mean±SD), n=147] and in the amounts of collected pheromone (47.7±63.3 ng). Furthermore, large daily fluctuations were also observed for individual females. In the field, large variations were also found in the quantities of collected pheromone among the individual females ranged from 0.57 to 24.7 ng/2 min [8.9±6.06 ng (mean±SD), n=46]. These results provided evidence of heterogeneity in the feral females with respect to the pheromone release in the field.

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Following baculovirus infection, the level of host messenger RNA (mRNA) declines and the synthesis of host proteins is shutoff in virus-infected cells. To comprehensively understand the regulation of host gene expression by Bombyx mori nucleopolyhedrovirus (BmNPV), we took a complementary DNA (cDNA) subtraction approach. Northern blot analysis was then performed to confirm whether obtained clones are differentially expressed. From these analyses, we obtained 4 down-, 7 up- and 2 non-regulated host gene candidates during the early stage of infection. Sequence analyses showed that these may encode proteins involved in transcription, cell cycle, cell adhesion, protein degradation, apoptosis or energy metabolism. We then measured the ADP/ATP ratio to address the response of host energy metabolism upon baculovirus infection. The ADP/ATP ratio showed cell death-like rapid increase following BmNPV infection with a transient decrease during 12–24 h post-infection (p.i.). Taken together, our results suggest that general events in host cells are controlled at the level of mRNA expression by BmNPV infection.

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Traps baited with dried soybeans and a synthetic aggregation attractant pheromone were more effective than traps baited with synthetic aggregation pheromone alone against the bean bug, Riptortus clavatus. Dried soybeans alone did not attract bean bugs, so this difference was not due to the attractiveness of the dried soybean itself. The known components of the aggregation pheromone were detectable only in extracts of a few individual attracted bugs; however, all the attracted male bugs had (E)-2-hexenyl hexanoate, which has been identified as an alarm pheromone in this species. This component was present in higher amounts in extracts of male or female R. clavatus that had been fed on soybeans than that of starved males or females. In the experiments, the attractiveness of tetradecyl isobutyrate, which is an essential component of aggregation pheromone, was increased by the addition of (E)-2-hexenyl hexanoate. These results suggested that (E)-2-hexenyl hexanoate is one of the components of the attractant aggregation pheromone of R. clavatus and that it may act as a synergistic composition but not a repellent. It is hypothesized that the pheromonal process related to food exploitation in R. clavatus includes positive feedback since attracted bugs stay to feed at sites and continuously release (E)-2-hexenyl hexanoate.

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