Six species of legume or cereal-feeding aphids, Acyrthosiphon pisum, Aphis craccivora, Megoura crassicauda, Rhopalosiphum maidis, Rhopalosiphum padi and Sitobion akebiae (Hemiptera: Aphididae), were tested as candidates for alternative hosts of Aphidius gifuensis (Hymenoptera: Braconidae), an indigenous natural enemy attacking vegetable pest aphids Aulacorthum solani and Myzus persicae (Hemiptera: Aphididae). A. pisum, R. maidis and S. akebiae were accepted by A. gifuensis. S. akebiae showed the most successful parasitism by A. gifuensis among the six aphid species tested, with a mummification rate of 71.7% and emergence rate of 96.7%. No parasitism was observed on R. padi, an alternative host available in the banker-plant system with an exotic parasitic wasp, Aphidius colemani (Hymenoptera: Braconidae). A. gifuensis females reared on S. akebiae had the same developmental period and body size as those reared on M. persicae, with no significant differences. They also demonstrated successful parasitic performance in A. solani and M. persicae. These results suggest that S. akebiae should be a promising alternative host for use in a banker-plant system with A. gifuensis.

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The harmful side effects of 11 pesticides, 5 acaricides, and 10 fungicides on nymphs and adults of the predatory mirid bug Pilophorus typicus Distant (Heteroptera: Miridae) were determined by dipping them into solutions of each chemical. Two insect growth regulators (IGRs), buprofezin and cyromazine, were not harmful to nymphal survival of P. typicus on the fifth day. Flufenoxuron, lufenuron, and novaluron (also IGRs) were seriously harmful to nymphal survival of P. typicus on the fifth day. IGRs that were deleterious to nymphal survival were probably harmful because they regulated molting. Three insecticides, buprofezin, cyromazine, and pyridalyl; one acaricide, bifenazate; and four fungicides, boscalid, captan, iprodione, and triadimefon, were found to be inert pesticides for nymphs and adults of P. typicus.

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Gap junctions are intercellular junction apparatus found in almost all multicellular animals and are involved in direct intercellular communication. Those of invertebrate animals consist of the innexin protein family. We developed antibodies against peptide fragments of Bombyx mori innexin 2, and examined tissues of Periplaneta americana by Western blotting, immunohistochemistry and immunoelectron microscopy. Intense immunoreactivity of innexin 2 was found in the midleg, gizzard and thoracic muscular tissues. Immunoelectron microscopy showed that immunogold particles of innexin 2 were aggregated around cell adhesion structures between muscle fibers. These results suggest that innexin 2 is expressed in the muscle cells of cockroaches and is involved in synchronization of muscle contraction.

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A cavity exists between the thorax and abdomen in Pieris brassicae (Lepidoptera: Pieridae) and Pieris rapae crucivora pupae. In this paper, it was investigated whether air swallowing occurs at the pupal ecdysis and the relationship between the swallowed air and cavity formation by MRI measurements of P. brassicae and six other lepidopteran species after pupation. In P. brassicae, air swallowing was observed at the pupal ecdysis with air found in the esophagus immediately after pupation. The size of the air pocket was larger in non-diapause pupae than diapause pupae; however, no marked cavity was found between the thorax and abdomen in both diapause and non-diapause pupae. As time lapsed, the air pocket became smaller and moved towards the abdomen with a reduction in the size of the digestive tract. The air disappeared within 6 to 18 h after pupation. Conversely, the cavity became larger 12 h after pupation in both diapause and non-diapause pupae. Twenty-four hours after pupation, a distinct cavity was formed. The swallowed air appears to be involved in cavity formation. In six lepidopteran species, air was also found in the esophagus immediately after pupation. The size of this air pocket was also larger in non-diapause than diapause pupae in all species with a diapause stage. This is the first paper to describe that lepidopteran species swallow air at the pupal ecdysis and the air pocket is larger in non-diapause pupae than diapause pupae.

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The small brown planthopper, Laodelphax striatellus (Fallén), is one of the major insect pests of rice in East Asia. This species is known as a vector insect of Rice stripe virus, and has been believed to show strong indigenousness, unlike other migratory rice planthoppers, the brown planthopper and the whitebacked planthopper. Large trap catches of L. striatellus with high viruliferous rates were recorded in western Japan on a windy day in early June 2008, and subsequently, rice stripe diseases spread in these regions. The migration source was estimated using backward trajectory analysis, and found to be Jiangsu Province, China. Laodelphax striatellus with high viruliferous rates and rice stripe diseases has occurred markedly throughout Jiangsu Province since 2004, and early June is the wheat harvest season, which could serve as a stimulus for planthopper emigration. Insecticide susceptibility of populations collected in rice fields both in western Japan and Jiangsu were compared by a topical application method. Both Chinese and immigrant populations showed resistance only against imidacloprid, whereas Japanese local populations showed resistance only against fipronil. Collectively, this evidence suggested that the overseas migration of viruliferous L. striatellus from China to western Japan occurred and subsequently caused rice stripe diseases in the areas to which insects immigrated.

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The corn leaf aphid, Rhopalosiphum maidis (Fitch) is one of the most important pests of maize with worldwide distribution. The use of relatively resistant corn hybrids may lessen the harmful effects by this aphid; we therefore compared population growth parameters of R. maidis reared on six commonly grown maize hybrids in Iran, namely K3640/3×MO17, Simon, SC704, EXP1, VRE26×K18 and VRE27×K18. The experiments were carried out under conditions of 25±1^oC, 60±10% RH, and a photoperiod of 16L8D. The development time and survival of aphid nymphs differed significantly among the maize hybrids tested. We also observed significant differences in aphid fecundity, resulting in large variations in population growth parameters, such as the intrinsic rate of natural increase (r_m), net reproductive rate (R₀), finite rate of increase (λ) and doubling time (DT). The r_m values were highest for aphids reared on maize hybrids EXP1 and VRE27×K18, lowest for aphids reared on hybrid K3640/3×MO17, and intermediate for aphids reared on hybrids VRE26×K18, SC704 and Simon. Consequently, these results may offer useful information for planning a comprehensive program for IPM of the corn leaf aphid in Iran.

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The continuous usage of pyrethroids against insects has provoked the emergence of insecticide resistance that has become a major obstacle to disease vector control. The knockdown resistance (kdr) voltage-gated sodium channel gene is regarded as a key to understanding the mechanism of resistance to pyrethroids. The main purpose of this study is to identify point mutations in the sodium channel gene associated with deltamethrin resistance in Aedes aegypti. Two mutations in the IIS6 domain of the channel, S989P and V1016G, were identified as possible candidates responsible for the emergence of deltamethrin resistance in Ae. aegypti Khu Bua strain. As S989P and V1016G mutations are located within the IIS5–S6 loop and IIS6 near the ion filter and binding site, these mutations might enhance pyrethroid resistance. Allelic variation in the sodium channel gene is thought to be one of the principal molecular mechanisms regulating pyrethroid resistance in mosquitoes.

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Insects sometimes invade different habitats in new territory compared to their original habitat. In the present study, the seasonal abundance of an exotic leaf beetle, Ophraella communa LeSage (Coleoptera: Chrysomelidae), which invaded Japan from North America in 1996, was investigated from April to October 2003 on two host plants, the common ragweed Ambrosia artemisiifolia L., and the giant ragweed A. trifida L., in Okayama City, Japan. Two peaks of population abundance were found on both plants within the year. Many O. communa were found on A. trifida growing on a hill area (land), whereas no insects were found on A. trifida growing on the bank of a riverbed (river), where the plants occasionally suffered water inundation. More pupae were found on the underside of plant leaves than on the surface of leaves, stems, and flowers; however, the pupation sites of the plants differed in September. No parasitoid or fungus was found in the laboratory and field, but predators were observed in the field in 2003, the fifth year after O. communa invaded Okayama. The results showed that the beetles fed on A. artemisiifolia as well as A. trifida in Japan, which is not reported as a host plant at their origin.

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The white grub beetle Dasylepida ishigakiensis is distributed in the southwestern part of the Ryukyu Islands of Japan. In addition to the three previously recognized local populations occurring in natural forests of Iriomote-jima and Ishigaki-jima Islands, and sugarcane fields in the Miyako region, including Miyako-jima and Irabu-jima Islands, a new population was collected from farmland on Ishigaki-jima in January 2007 and 2008. In order to examine the relationships among these populations, we performed molecular phylogenetic analysis of 150 individuals based on the sequences of two mitochondrial DNA fragments (1.9 kb in total length), one containing a portion of the cytochrome oxidase subunit I gene and the other containing a portion of the 16S rRNA gene. As a result, individuals were clearly divided into six haplotypic groups. The newly discovered Ishigaki-jima population contained three haplotypic groups, two of which were specific to this population and the third of which was the same as one of the two haplotypic groups detected from the Miyako region, indicating insect movement between Ishigaki-jima and the Miyako region. Based on these results, we discuss the direction of insect dispersal in conjunction with the evolutionary history of insular populations of this species.

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The dispersal distance of the larvae of the sugarcane click beetle Melanotus okinawensis Ôhira (Coleoptera: Elateridae) in soil was estimated using the mark-recapture method. Grid lines with 30-cm intervals were set 10×10 in a fallow field after sugarcane harvest. Sixty marked larvae were released twice at the center of the grid. The tip of the corneous process on the last abdominal segment was cut and used for marking. Germinating rice seed baits were placed at the 10×10 intersection points of grid lines at a depth of 10 cm in order to recapture larvae. All traps were examined at two-day intervals. The estimate of lifetime natural mean dispersal distance (±SE) was 105.6 (±20.1) cm. The estimate of the natural survival rate per day was 0.861. The diffusion coefficient was estimated to be 613.

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In estimating the population abundance by the mark-recapture method using male-attractant pheromone traps, the release of sterile males is preferable, because they do not increase the reproductive rate of wild females by increasing the mating rate. We estimated the influence of gamma radiation on males of the sugarcane click beetle Melanotus okinawensis Ôhira (Coleoptera: Elateridae) to determine an appropriate dose of gamma radiation in laboratory and field experiments. The hatchability of eggs was examined for 0, 50, 70, 90, and 150 Gy. No hatchings were observed in eggs laid by females which mated with males treated with doses of 70, 90 and 150 Gy. The longevity of adults in the laboratory was estimated with 0, 30, 50, 70, 90, 150, and 200 Gy. Analysis by the proportional hazard model indicated that irradiation significantly reduces the survival rate in the laboratory even if the dose is 30 Gy. Mean dispersal distance in the field was estimated with 0, 50, 90, and 150 Gy. Three hundred marked beetles for each dose were released at the center of Ikei Island on 1 and 3 April 2003. The estimates were 274, 219, 192, and 289 m, respectively, and we could not detect a significant influence of irradiation on the mean dispersal distance. Field survival rates were estimated using Jolly-Seber, Yamamura, and Yamamura B methods at Okinawa Prefectural Experiment Station in Naha for two doses of irradiation, 0 and 90 Gy; we could not detect significant differences between the two survival rates. The mortality added in the field was estimated to be much greater than the mortality caused by irradiation when we focus on the experiment within 12 days after release, if the dose of irradiation is lower than 90 Gy. It was therefore concluded that 90 Gy will be an appropriate dose for preparing sterile males to estimate population abundance and survival rate in the field within 12 days after release.

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In order to establish the optimal thermal conditions for mass rearing of the predatory mirid bug Pilophorus typicus, we investigated the effect of temperature on the development and fecundity of this bug at 6 constant temperatures (17.5, 20.0, 22.5, 25.0, 27.5, and 30.0°C) under a 16L8D photoperiod. The developmental period of P. typicus from egg to adult at different temperatures was not affected by sex. The developmental zero (T₀) and thermal constant (K) of females from egg to adult were 12.0°C and 357.1 day-degrees, respectively. The corresponding values for males were 12.1°C and 357.1 day-degrees, respectively. The mean generation time (T) of P. typicus decreased with an increase in temperature from 17.5°C to 30.0°C. Among the temperatures investigated, the net reproductive rate (R₀) was highest at 25.0°C, whereas the highest intrinsic rate of natural increase (r_m) occurred at 27.5°C. These results indicate that the optimal temperature for the mass rearing of P. typicus is between 25.0°C and 27.5°C.

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The ambrosia beetle, Platypus quercivorus, is an insect vector of the Ascomycete fungus, Raffaelea quercivora, the causal agent of Japanese oak wilt disease. In this study, we compared the nucleotide sequences (937–955 bp) of the nuclear 28S rDNA fragment, including the D1 and D2 expansion segment, among local populations of the beetle in Japan. Sequence analysis of 81 beetles from 32 collection sites ranging from the Ryukyu Islands to northern Honshu Island showed seven types of sequences, many of which were separated among different geographic areas. Phylogenetic analysis showed that these sequence types were separated between two deeply divergent genetic groups, suggesting the necessity for taxonomic reexamination of this species. DNA typing of beetles and oak wilt status at the collection sites indicated that several genetically divergent beetle populations are associated with the incidence of the disease. This is the first investigation of genetic variation in the ambrosia beetle across Japan.

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Despite plant quarantine systems, many organisms have been unintentionally introduced by the rapid expansion of international trade. Xylocopa tranquebarorum, a large species of carpenter bee that nests in bamboo shoots, was introduced into Japan approximately 5 years ago and, along with its specifically associated mite, has established populations in Toyota and Nagoya in Aichi Prefecture and Anpachi in Gifu Prefecture. Because X. tranquebarorum only nests in dead bamboo shoots and because its associated mite differs from the mite species associated with X. tranquebarorum in Taiwan but is morphologically similar to the species described in India, Indonesia, and China, we suspect that X. tranquebarorum and its mite were introduced via processed bamboo shoots from continental Asia. Because the most probable pathway of associated microorganisms is host introduction, biological and ecological information, such as an inventory of symbionts, is crucial to avoid the risk of invasive symbiotic microorganisms. Although X. tranquebarorum may become a pest in the bamboo industry if its distribution is expanded by human transport, its associated mite is suspected to be of low risk as house dust but to have a high contamination risk for the Japanese endemic mite, Sennertia alfkeni, associated with native Japanese carpenter bees.

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The learning systems of the parasitoid Ascogaster reticulata were investigated using 5 authentic chemicals from tea leaf. The learning efficiency for geraniol and linalool was higher than for the other 3 components, (Z)-3-hexenol, methyl salicylate and benzyl alcohol. Discrimination between geraniol and linalool became clear when the number of conditionings increased. Furthermore, A. reticulata females preferred the chemical information after successive oviposition experience and the newly learned information. A 2-choice bioassay using a mixture of these tea leaf components suggested that geraniol and linalool play a key role in the discrimination of mixtures. However, A. reticulata females could also discriminate minor components in the mixture. They use several key components in the discrimination of plant species as well as other hymenopteran species. Increased preference for a certain plant species after successive oviposition experience of the same plant is adaptive for female's host-searching behavior in the field.

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