Here we review the bioindicator potentials of several arthropod groups in forest management. First, we describe the indicator potentials of frequently used arthropod groups in general forest management, and then evaluate ecosystem function and plural taxonomic groups to infer forest biodiversity. We then review indicator potentials of arthropod groups to explore the ecological consequences of forest management practices. Different arthropod groups respond differently to forest management. Ants, carabid beetles, and spiders often respond to local-scale, disturbance-induced vegetation development caused by thinning and can be used to infer the ecological suitability of forest management treatments. Dung beetles and moths respond to habitat alterations caused by forest fragmentation and can indicate the suitability of landscape-level forest management techniques. Butterflies and cerambycid beetles respond highly positively to the presence of herbaceous plants and understory trees and can be used to infer the integrity of thinning treatments in forest management. Syrphid flies, which are strong flyers associated with vegetation complexity, can be used as bioindicators of landscape-level forest management practices. Monitoring regulatory service providers may also help when designing forest management practices. We propose using arthropod bioindicator groups to effectively design and assess ecologically sustainable management plans for both natural and plantation forests.

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A remarkable reduction of the post-hatching survival rate caused by adopting the furcellaran solution (a viscous liquid, hereafter FS) as an egg-seeding agent has become a problem during development of mass-rearing methods for the West Indian sweet potato weevil (Euscepes postfasciatus) using an artificial diet. We hypothesized that FS physically inhibits the feeding of hatched larvae on the diet, and predicted that removing and/or drying FS after egg seeding would improve the survival of E. postfasciatus. To confirm this prediction, we examined the effects of two post-egg-seeding treatments (placing absorbent paper on the diet surface and ensuring air permeability of the rearing tray) on the survival and development of the weevils. Neither of the two treatments worked well individually, but they exhibited a clear synergistic positive effect on weevil survival. Their survival rate jumped from 2% to 40% when these two treatments were combined, without any adverse effects on the developmental period and the adult body size. These treatments thus enabled the FS-based egg-seeding method, which is much simpler than previous methods, clearly contributing to the establishment of a mass-rearing system for E. postfasciatus.

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It has been reported that volatiles from broad bean plants, Vicia faba (cv. ‘the Sutton’) infested by the pea aphid, Acyrthosiphon pisum, attract a specialist parasitoid Aphidius ervi, collected from populations in England, Italy and Bulgaria, which had no previous experience of the host-infested plant volatiles. Aphidius ervi collected in Hokkaido, Japan were also attracted to volatiles from host-infested broad bean plants (cv. ‘Nintoku Issun’) in preference to those from intact plants in a Y-tube olfactometer when the wasps were allowed to emerge on the infested plants, but wasps that had emerged in a clean Petri dish showed no significant choice between the two odor sources. When artificially exposed to the infested plant volatiles during emergence from the mummy, the wasps showed a significant preference for infested plant volatiles over those from intact plants. In further studies in a wind tunnel, significantly more wasps landed on infested plants than on intact plants when wasps were exposed to infested plant volatiles. Naïve wasps, however, did not show a higher landing response to infested plants. These data suggest that learning is required by A. ervi of the Hokkaido strain for their response to infested plant volatiles in their host searching behavior.

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Two experiments were performed in the laboratory to understand the relationships between oviposition preference and larval performance of the two predatory hoverfly species, Episyrphus balteatus de Geer and Metasyrphus corollae Fabricius. We first conducted laboratory experiments to understand the nature and relative strengths of intraguild predation between the larvae of three ladybird species, Harmonia axyridis Pallas, Propylea japonica Thunberg, and Scymnus posticalis Sicard, and two predatory hoverfly species. The interactions between larvae of the three ladybird and two hoverfly species differed depending on the species and developmental stages involved: the relationships between H. axyridis or S. posticalis and the two hoverfly larvae tended to be asymmetric with H. axyridis being a superior species and S. posticalis an inferior species, although the reverse was true for each of these two species when small larvae were paired with large larvae of the hoverflies. The ladybird, P. japonica, had both asymmetric and symmetric relationships depending on the hoverfly species with which it interacted. Secondly, we tested the preference and performance hypothesis for hoverflies, by determining whether hoverfly oviposition preference was related to the risk of intraguild predation posed by the presence of a ladybird larva in an aphid colony. Oviposition preference in relation to larval performance of the two hoverflies differed between the species: E. balteatus females tended to adjust their rate of eggs laying in response to the presence of ladybird larvae, while similar responses of M. corollae females were weak. The relationship between oviposition preference and larval performance in hoverflies is discussed.

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Riptortus clavatus Thunberg (Heteroptera: Alydidae) is an important soybean pest in Korea and Japan. Chemical application is a common control method against R. clavatus although it is not always effective at reducing crop damage. As a biological control, the release of refrigerated stink bug eggs has been suggested because the eggs become non-viable but can still be parasitized by parasitoids. We evaluated the inoculation of refrigerated eggs of R. clavatus as a method to enhance natural parasitism. Overall, 9,000–10,600 refrigerated eggs of R. clavatus were inoculated in soybean fields. A higher seasonal parasitism rate on both natural and released host eggs was found at the treated sites. Gregarious parasitoids, including Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and solitary Gryon japonicum Ashmead (Hymenoptera: Scelionidae), emerged from natural eggs. On the released eggs, the parasitism rate by gregarious parasitoids was greatly reduced for an unknown reason. The proportion of bean pods with stylet sheaths as an index of crop damage was also significantly reduced; however, neither the seasonal number of unparasitized eggs nor nymphs and adults of R. clavatus was affected by host egg inoculation. This is the first trial to inoculate non-viable host eggs to enhance natural parasitism.

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The majority of insects that overwinter in the adult stage copulate post-winter. Some such insects copulate not only post-winter, but also pre-winter and/or during winter. In Orius species, only females overwinter. As they have no chance to copulate post-winter, they do so pre-winter. We expected pre-winter copulation to be associated with increased survival of females during overwintering; therefore, we tested the effects of pre-winter copulation on winter survival in females of three Orius species, O. sauteri, O. nagaii and O. strigicollis. Under semi-field conditions, clear differences in overwintering survival were observed between copulated and virgin females in the late overwintering period. Overwintering success of copulated females was higher than that of virgin females; however, copulation frequency did not affect winter survival of females. With regard to the mechanism increasing winter survival, two possible explanations arose from this study. The first is the donation of nutrients from males through copulation, and the second is that copulation affects diapause syndrome and/or behavioral changes in females.

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Meteorus pulchricornis is a solitary endoparasitoid of various lepidopteran larvae that attacks free-living hosts exposed on plant foliage. We tested the necessity of host movement for oviposition behavior in M. pulchricornis using dummy hosts as well as natural host larvae (Spodoptera litura). We quantified the occurrence of three steps in oviposition behavior, i.e., host orientation, oviposition stance, and oviposition attack, to natural hosts under light and dark conditions. We also examined the incidence of these behaviors on natural hosts, moving dummy hosts, and motionless dummy hosts under light conditions. Few successful attacks occurred on natural hosts under dark conditions and no oviposition attempts were made against motionless dummy hosts. These results indicate that visual cues from moving host larvae are necessary for successful oviposition. Furthermore, host movement seems important for female wasps to orient the ovipositor toward the host body, since the location of the oviposition attack on natural hosts changed markedly with the mode of host movement.

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A gall midge (Diptera: Cecidomyiidae) that was previously misidentified as Epimyia sp. has been known as a serious pest of chrysanthemum (Asteraceae) cultivated for ornamental and medical purposes in China. Based on DNA sequencing data and morphological features, we concluded that this gall midge belongs to the genus Rhopalomyia and is identical to gall midges collected from Chrysanthemum indicum on Jeju Island, Korea and in Hubei Province, China. We describe the gall midge as a new species, Rhopalomyia longicauda, and provide details of the host range, gall shape, distribution, life history, and pest status. We also urgently warn those who are responsible for growing chrysanthemums against importing potentially infested plants into Japan or Korea (except Jeju Island).

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The carrion beetle, Eusilpha japonica, is a carrion feeder that roams on forest floors searching for carrion. A field survey using pitfall traps with putrefied meat or without meat was carried out to examine the effect of carrion odor on the attraction of adults in the cedar forest. The sex distribution of the beetles captured in the pitfall traps suggested that the carrion odor might attract females more strongly than males. The distribution pattern showed that males might search for mates as well as for food. The daily food intake of adults collected in the field was measured in the laboratory. Lone females fed on the meat twice as much as lone males. A positive relationship between the cumulative quantity of food intake until the first brood and the clutch size suggested that the quantity of food intake during the pre-oviposition period was critical.

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We examined the effects of wall structure and light intensity on the settlement of the predatory mite Euseius sojaensis (Ehara). The mite preferred to settle beside higher walls and in wall gaps where it could make contact with two walls. Light intensity did not independently affect mite settlement; however, mites preferred to settle under moderate light near walls. These results suggest that a wall structure is an essential factor for mite settlement. These mites preferred to settle in the vicinity of leaf veins, which might be reflected in their preference for wall structures.

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The midgut of the silkworm Bombyx mori contains two types of trehalase: soluble and membrane-bound. The trehalose concentration in larval hemolymph remains substantially high through the feeding period of the last (fifth) larval instar, despite appreciable trehalase activity through this period. We found that B. mori larval hemolymph contains two types of trehalase inhibitor, a proteinaceous inhibitor (inhibitor-P) and an inhibitor that is extractable with methanol and ethanol (inhibitor-M). Both inhibit the two types of trehalase, but with different sensitivities. Inhibitor-P inhibited soluble trehalase (ST) more effectively than membrane-bound trehalase (MT), while inhibitor-M inhibited MT slightly more than ST. The inhibitory activity of inhibitor-M was high during the early to middle feeding period, followed by a sudden decrease during the late feeding period. Inhibitor-P activity increased throughout the feeding period, and markedly decreased 2 days after gut purge. Thus, the two inhibitors exhibited stage-specific changes in the hemolymph, indicating coordinated inhibitory activity. Therefore, trehalose concentration regulation in the hemolymph appears to be complex, consisting of at least two inhibitors and two types of trehalase.

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Nested PCR amplification of a Spodoptera litura nucleopolyhedrovirus (SpltNPV) lef-8 gene fragment was performed on egg masses and larvae of S. litura, and resulted in detection of a latent SpltNPV in 20.0% of “healthy” laboratory stock samples, and in 22.6% of samples collected at different periods and in remote places in Kagoshima Prefecture. The PCR product sequences showed 99% similarity to the published lef-8 sequence of SpltNPV, confirming that the amplification products were derived from SpltNPV. Further, cross-inoculation of laboratory stock S. litura larvae with Mythimna separata NPV (MyseNPV) activated the latent virus, which provoked a change in the virulence of MyseNPV samples collected from cadavers of S. litura. Our data suggest that caution should be taken when using S. litura as a host to produce heterologous NPVs.

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In the present study, we evaluate the toxicity of six insecticides to Brevicoryne brassicae (L.) (Hemiptera: Sternorrhyncha: Aphididae), predatory coleopterans Cycloneda sanguinea (L.) (Coccinellidae) and Acanthinus sp. (Anthicidae), and the hymenopteran parasitoid Diaeretiella rapae (McIntosh) (Braconidae, Aphidiinae). Late-instar nymphs of B. brassicae and adults of C. sanguinea, Acanthinus sp. and D. rapae were exposed to nine concentrations of acephate, deltamethrin, dimethoate, methamidophos, methyl parathion and pirimicarb. Selectivity, toxicity, and tolerance ratios were calculated from LC₅₀ values to determine insecticide toxicity to B. brassicae and natural enemies as well as insecticide tolerance of the natural enemies. Pirimicarb was highly selective to Acanthinus sp., C. sanguinea, and D. rapae. Dimethoate, methamidophos and methyl parathion also showed selectivity to C. sanguinea and Acanthinus sp., but not to D. rapae. Methamidophos was the least potent insecticide against B. brassicae exhibiting the highest LC₅₀ amongst the products tested and was more toxic to the D. rapae relative to the aphid. Overall, the predators Acanthinus sp. and C. sanguinea were more tolerant to the insecticides than was the parasitoid D. rapae. The role of insecticides in IPM systems of brassica crops is discussed based on the toxicity to B. brassicae and selectivity to natural enemies.

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Previously, we reported that virus-like particles of Meteorus pulchricornis (MpVLPs) induced apoptosis in hemocytes of its host, Pseudaletia separata, and that MpVLPs seem to especially damage the granulocyte population in vivo. The present study was conducted to elucidate more clearly the distinct behavior of two hemocyte populations in response to MpVLPs or parasitization. First, we examined the differences between plasmatocytes and granulocytes in their sensitivity to MpVLP-induced apoptosis and also in changes of their numbers after parasitization. MpVLPs induced apoptosis in both hemocyte species in vitro. The number of plasmatocytes increased slightly after parasitization in vivo unlike that of granulocytes. The BrdU incorporation assay indicated that the parasitization or the injection of venom containing MpVLPs (V(+)VLP) enhanced the proliferation of plasmatocytes and suppressed that of granulocytes, accounting in part for the distinct responses shown by the respective hemocyte populations. Next, we examined the effects of V(+)VLP on hematopoietic organs (HPOs), major tissues for hematopoiesis of P. separata. A large number (approximately 70–80%) of the cells released from cultured HPOs were determined to be plasmatocytes by the morphology and response to growth-blocking peptide. The injection of V(+)VLP did not affect HPOs in terms of the hematopoietic activity and hemocyte species released. These results, together with our previous data, suggest that the plasmatocyte population was maintained by both supply from undamaged HPOs and the propagation of circulating cells during the initial phase of at least 24 h post-parasitization, while MpVLPs caused apoptosis irrespective of hemocyte species.

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Beauveria bassiana strain HF338 had the highest pathogenicity among 77 isolates to larvae of the chestnut weevil, Curculio sikkimensis (Heller) (Coleoptera: Curculionidae). Its pathogenicity at 25°C was similar to that of Metarhizium anisopliae strain HF293. Its pathogenicity at 15°C remained high, whereas that of M. anisopliae HF293 was greatly reduced. Its pathogenicity to chestnut weevil adults and nut fruit moth, Cydia kurokoi (Amsel) (Lepidoptera: Tortricidae), was also higher than those of M. anisopliae HF293. In field tests, the survival rate of chestnut weevil larvae decreased to 2.9% when B. bassiana HF338 was applied at 1×10¹¹ conidia/pot. The high pathogenicity of B. bassiana HF338 makes the strain a potential microbial agent for the control of chestnut pests.

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Founding queens of the obligatory social parasite ant Polyergus samurai usurp the host Formica japonica colony. The queen secretes chemicals from its gaster when killing the host queen. At this time, the parasite queen is hardly attacked by host workers. We hypothesized that the queen's secretion acts as a repellent to deter host workers' aggression during host queen killing. Gas chromatograph-mass spectrometry analyses confirmed that the chemical composition of Dufour's gland contents of P. samurai queens was almost identical to the chemicals remaining on the body surface of host Formica queens killed by them. Host F. japonica workers were used for bioassays. In an encounter with an intruder ant, the workers' aggression to the intruder was reduced significantly when Dufour's gland extract was applied to the intruder. Treatment of workers with the gland extract significantly increased the receding behavior of nestmates. The host workers receded from a glass dummy treated with the gland extract. The time necessary for a worker to get over a barricade applied with gland extract was significantly longer than that of controls. These results strongly suggest that Dufour's gland secretion acts as a repellent allomone.

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Nonviruliferous adults of Bemisia tabaci Q biotype were released at different densities onto Tomato yellow leaf curl virus (TYLCV)-infected and healthy tomato plants (Lycopersicon esculentum ‘House Momotaro’) in the laboratory. The number of progeny was related to the release density of whiteflies but not to the presence of TYLCV infection on tomato plants. Q biotype adults reared on tomato plants that were either healthy or infected with TYLCV were allowed to oviposit on healthy tomato plants in the laboratory. There were no significant differences in survival rate and fecundity between viruliferous and nonviruliferous whiteflies. Q biotype adults were also released on TYLCV-infected and healthy tomato plants grown in glasshouses, and then the number of adults was investigated for two consecutive generations. In both generations there was no significant difference in the whitefly reproductive rate per generation between those released on infected and healthy tomato plants. These results suggest that symptomatic TYLCV infection of susceptible tomato plants has little effect on the reproduction of the virus's vector, the Q biotype of B. tabaci.

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The virulence of laboratory strains of the brown planthopper (BPH), Nilaparvata lugens (Stål), and the whitebacked planthopper (WBPH), Sogatella furcifera (Horváth), collected in Japan between 1966 and 2005, was evaluated using rice differential varieties carrying different planthopper resistance genes. The BPH strain collected in 1966 was avirulent to all the rice varieties tested. In contrast, the 1989, 1999 and 2005 strains were virulent to Mudgo, which carries Bph1. The 1999 and 2005 strains were virulent to ASD7 (bph2). Thus, the virulence status of the laboratory BPH strains was the same as in previous reports. The 1989, 1999, and 2005 WBPH strains were virulent to N22 (Wbph1), Mudgo, ASD7, Babawee (bph4) and Chin Saba (bph8); the 1999 and 2005 WBPH strains were also virulent to ARC10239 (Wbph2). Although the virulence status of WBPH in Japan has not previously been studied, the present results suggest that the effectiveness of the Wbph1 resistance gene broke down before 1989, while that of Wbph2 broke down between 1989 and 1999. The present study showed that long-term mass rearing in the laboratory has not affected virulence status. Thus, these strains will be useful to analyze resistance genes against BPH and WBPH.

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To improve the procedures for estimating the abundance of the rice bug, Leptocorisa chinensis Dallas (Heteroptera: Alydidae), field monitoring using traps baited with synthetic attractant was conducted in Tsukuba, central Japan from 2002 to 2006. A mixture of (E)-2-octenyl acetate and 1-octanol, in a ratio of 5 : 1 and incorporated into a plastic pellet, was used as bait on sticky boards and placed at study sites from early June to the end of October. The attractant-baited traps were able to detect the starting of the migration period of the overwintered generation and the population increase of the first generation. The number of trapped insects decreased rapidly after early September, while the number of insects in second generation increased in the grassy weeds field. The decreased temperatures and shorter day-length of autumn (which will have induced reproductive diapause) may have affected the attractiveness of the baited traps. The ratio of males to all captured L. chinensis was 0.88–0.96. Most captured adults had no food in their stomachs, and most males were sexually mature. These results indicate that the males trapped had actively moved for two possible reasons: to search for food and/or to search for females. Based on comparisons between the results of baited trap monitoring and sweep-net surveys, it was considered that immigrant period and density of L. chinenis in the poaceous plants fields depend on the density of dispersal individuals and the heading period of the plants.

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Outbreaks of the migratory locust, Locusta migratoria L., occurred in 2005–2006 on Iheya Island, Okinawa, Japan. The present study was initiated in autumn 2006 to investigate the morphological characteristics of adult locusts after the outbreaks. Although most adults collected in the field showed morphometric traits typical of solitarious forms, a few adults were characterized by dark body coloration, a concave pronotum, relatively small F/C ratios and large E/F ratios, often recorded in outbreaks. Locusts were sampled every month from October 2006 to March 2007 to determine the status of ovarian development. A few females with developing oocytes or eggs were always present in the samples, but most females had small oocytes until January. The mean time required to start oviposition after transfer to the laboratory (12L12D and 30°C) was 16–18 days in females collected in the autumn, but decreased significantly in those collected in late December onward. Eggs had a capacity for diapause at 20°C, but not at 25 or 30°C. The induction of diapause was influenced by the parental photoperiod. These results suggest that this locust overwinters mainly in the adult or egg stage on this island.

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Adult females of Eretmocerus eremicus and Encarsia formosa, aphelinid parasitoids of Bemisia tabaci and Trialeurodes vaporariorum, are known to feed on honeydew and hemolymph of both whitefly hosts. Because these easily accessible food sources contain different sugars, we selected glucose, sucrose and fructose as host-honeydew sugars and trehalose and glucose as host-hemolymph sugars and determined the effects of these four sugars on parasitoid longevity in the laboratory. Each of the four sugars increased the female longevity of both parasitoids, and for Er. eremicus, there was no significant difference in longevity among the four sugars, but for En. formosa, trehalose had a significantly smaller positive impact on longevity than the other three sugars. We conclude that glucose, fructose and sucrose in the host honeydew and glucose in the host hemolymph greatly increase the female longevity of both parasitoids. We also conclude that Er. eremicus can also utilize trehalose fully in extending female longevity, while En. formosa can not. This suggests that host hemolymph containing trehalose is more important as a carbohydrate source for Er. eremicus than for En. formosa.

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