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Adult spermatogenesis of Polygonia c-aureum was compared between non-diapausing and diapausing butterflies before overwintering. This butterfly has seasonal polyphenism, i.e., summer and autumnal forms. Summer form butterflies that emerged in summer reproduce shortly after emergence, while autumnal forms that emerged in autumn mate in spring. Immatures were reared under either a long photoperiod, which produced the summer form without diapause or under a short photoperiod, which produced the autumnal form with diapause. We found almost no differences in adult spermatogenesis between the two seasonal forms, indicating that adult spermatogenesis is not related to adult diapause. Although adult diapause in the autumnal form is maintained under short photoperiods and terminated under long photoperiods, such a photoperiod did not affect the spermatogenesis of the autumnal form. Our earlier studies indicate that relatively few eupyrene and apyrene sperm are produced after overwintering. Although apyrene spermatogenesis occurred in young adults, eupyrene spermatogenesis did in a small scale before overwintering. These results suggest strongly that male autumnal form butterflies prepare the sperm until overwintering, which had been formed during the larval, pupal and young adult stages.

To provide fundamental information for the biological control of aphids in vegetable greenhouses, we compared the host ranges of four aphid parasitoid species, Aphidius colemani Viereck, Aphidius gifuensis Ashmead, Diaeretiella rapae (M’Intosh), and Ephedrus nacheri Quilis (Hymenoptera: Braconidae: Aphidiinae). The acceptability as host of 11 vegetable-pest aphids, Acyrthosiphon pisum (Harris), Aphis craccivora Koch, Aphis gossypii Glover, Aulacorthum solani (Kaltenbach), Brevicoryne brassicae (Linnaeus), Chaetosiphon fragaefolii (Cockerell), Lipaphis erysimi (Kaltenbach), Macrosiphoniella sanborni (Gillette), Macrosiphum euphorbiae (Thomas), Myzus persicae (Sulzer), and Uroleucon formosanum (Takahashi), in addition to five aphid species, Melanaphis sacchari (Zehntner), Rhopalosiphum maidis (Fitch), Rhopalosiphum padi (Linnaeus), Schizaphis graminum (Rondani), and Sitobion akebiae (Shinji) (Hemiptera: Aphididae) that serve as alternative hosts in banker–plant systems for the four aphid parasitoid species, were investigated. A newly emerged pair of parasitoid adults were provided to 100 aphids of each species on caged host plants in a 25 °C chamber for 24 h. The numbers of mummified aphids and emerged adults were counted in 10 trials for each aphid species. Aphidius colemani, A. gifuensis, D. rapae and E. nacheri parasitized four, two, three, and eight pest species, respectively, and four, three, three, and five alternative host species, respectively. Ephedrus nacheri had the broadest host range among the four species, and all the four species parasitized M. persicae, R. maidis, and S. graminum. This information will be useful for selecting candidate of biological control agents for aphids and for constructing banker–plant systems.

To evaluate the infection risk of Anoplophora malasiaca (Thomson) (Coleoptera: Cerambycidae) in two species of Japanese pine bonsais (Japanese black pine and Japanese white pine), feeding and oviposition preferences of female A. malasiaca to pine bonsai and mandarin orange were examined. A female was released into a net cage together with a pair of one pine bonsai and one mandarin orange. All mandarin oranges used in preference tests were damaged by feeding and deep biting scars from females, and larval frass ejection from the trunk was found in some mandarin oranges within 4 months of observation. However, these scars were found on only a few pine bonsais, and frass ejection was not found in any pine bonsais. No A. malasiaca larvae were detected in these pine bonsais. Therefore, frass ejection from trunks might be indicative of the presence of larvae. In field surveys at bonsai nurseries, no A. malasiaca adults were found on the pine bonsais and no pine bonsais exhibited frass ejection. Statistical analyses of these results suggested that the risk of A. malasiaca infestation in pine bonsais could be ruled out as a negligible level by confirming an absence from the trunk of frass ejection.

The insect growth regulator NC-184, a juvenile hormone mimic, prevents moulting to the adult stage in the desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae). Male nymphs treated in the penultimate or final nymphal instar with NC-184 exhibit precocious mating behaviour in the final instar. We examined whether this chemical affects the development of the internal reproductive organs of crowded nymphs. In treated males, both accessory glands and seminal vesicles were underdeveloped, and no sperm was found in the seminal vesicle, whereas these organs in control individuals had greatly increased in size 10 days after treatment, when all the insects had moulted to adults. Testis size in treated males was similar to that in controls, regardless of their smaller body size due to the inhibition of moulting. Oogenesis and development of spermatheca in females treated with NC-184 continued to some degree, but no eggs matured, unlike what occurred in the control. In conclusion, treatment of S. gregaria nymphs with NC-184 resulted in changes in the reproductive organs in both sexes.

The stone leek leafminer, Liriomyza chinensis (Kato) (Diptera: Agromyzidae) , is recognized as one of the most destructive pests of the bunching onion. Varietal resistance against L. chinensis has been reported in Allium fistulosum in Japan. We report a new method for evaluating the antibiosis of bunching onions with varietal resistance to L. chinensis by artificially inoculating leaves with L. chinensis eggs. New no-choice tests were performed via the collection and artificial inoculation of L. chinensis eggs into unifacial leaves with a plunger microsyringe and the quantification of the number of individuals that reached the pupal stage in the soil after 14 days of inoculation at 24 °C; these tests were established and conducted to determine the resistance categories of several varieties of A. fistulosum. Antibiosis studies revealed a significant difference in survival to the pupal stage, forewing lengths of adults and development time from the egg to pupal stages among the resistant and susceptible varieties of A. fistulosum, indicating that antibiosis is an important factor in the varietal resistance of A. fistulosum. Furthermore, the antibiosis of the highly resistant varieties ‘Beicong’ and ‘Kokusen natsuyo’ revealed egg killing defenses against L. chinensis.

Grazing damage to pasture plants by cervids results in economic losses and substantially increases production costs for dairy farms. Understanding both temporal and spatial variations in the risk of grazing damage to sown grasslands by deer will help in deciding suitable timing for culling and in prioritizing pastures and meadows for the introduction of damage prevention management, such as fencing and culling. Here, we assessed both the season and the sown grassland characteristics that attracted more sika deer (Cervus nippon) on a dairy farm located in a mountainous area of Gunma Prefecture in central Japan. We conducted spotlight counts on the farm during 2012–2015 to record the number of deer in 32 management units utilized as pastures or meadows. Deer utilized the grasslands year-round, but their numbers fluctuated seasonally. Deer utilization was the highest in November and the lowest in February. During the snow-free season (April–November), there were more deer in fertilized management units but fewer in cattle-stocked management units. During the snow season (December–March), more deer were found in management units with steeper terrain. Factors affecting deer utilization differed by season: the quality and availability of pasture plants were the primary drivers of deer utilization in the snow-free season, but only the availability of pasture plants drove utilization in the snow season. Farm managers should consider damage control plans for deer based on the risk of grazing damage, which fluctuates depending on both the season and the characteristics of management units.

In general, sperm produced in the testis are moved into the seminal vesicle via the vas deferens in insects, where they are stored. How this sperm movement is controlled is less well understood in locusts or grasshoppers. In this study, the effects of age, phase variation and pheromones on male sperm storage were investigated in the desert locust, Schistocerca gregaria (Forskål). In this locust, a pair of ducts, the vasa deferentia, connect the testes to a pair of the long, slender seminal vesicles that are folded approximately thirty times, and where the sperm are stored. We found that phase variation affected the level of sperm storage in the seminal vesicle. Moreover, adult males that detected pheromones emitted by mature adult males showed enhanced sperm storage compared with males that received the pheromones emitted from nymphs: The former, adult male pheromones are known to promote sexual maturation of immature adults of both sexes, whereas the latter, nymphal pheromones delay sexual maturation. Most mature adult males had much sperm in the vasa deferentia at all times examined, suggesting daily sperm movement from the testes to the seminal vesicles via the vasa deferentia. As adult males aged, sperm were accumulated from the proximal part to the distal end of the seminal vesicle. Many sperm remained in the seminal vesicle after mating. These results suggest that young or new sperm located near the proximal part of the seminal vesicle could be used for mating, whereas old sperm not used for mating are stored in the distal part of the seminal vesicle.

Sugarcane smut, caused by Sporisorium scitamineum, is one of the most important sugarcane diseases in Japan. Wild sugarcane, Saccharum spontaneum, is known to be a key breeding material to obtain high-yielding clones. In this study, we sought to identify Japanese wild sugarcane accessions with high resistance to smut. Thirty wild sugarcanes and three sugarcane cultivars were tested by the pinprick method. The results of the inoculation tests aided in identifying wild sugarcanes with high resistance to smut disease, namely JW90, Iriomote8, and Iriomote15. After screening the germplasm, progeny distribution of smut resistance from the inoculation test and dry matter productivity in the smut disease-free field were compared. The highly resistant wild sugarcane accession had a much better impact on progeny distribution of smut resistance compared with the susceptible accession. No relationship was found between smut resistance and dry matter productivity in both populations.

The reproductive durations of Myzus persicae (Sulzer) after parasitization by three species of Aphidiinae were compared and the mechanisms for differences in duration were examined. The lifetime fecundities of adult aphids parasitized by Aphidius colemani Viereck, Aphidius gifuensis Ashmead, and Diaeretiella rapae (McIntosh) were 3.96, 6.40, and 6.48, respectively. These values were much smaller than that of healthy adults (61.43 nymphs). The time of termination of reproduction by the aphids coincided with the time that the parasitic wasp larvae reached second instar. We infer that first-instar larvae of all three species initially attack conspecific and/or heterospecific competitors and that consumption of the aphid’s ovaries and other reproductive organs commences in the second instar. The modified intrinsic rates of natural increase (r parasitized) calculated from post-parasitized fecundity were 0.185 by A. colemani, 0.233 by A. gifuensis, and 0.234 by D. rapae. Parasitization of 100 % of the adult aphids by A. gifuensis or D. rapae decreased the growth rate to a minimum of 24.4 % while A. colemani more moderately suppressed the growth of the aphid population (39.9 %). We propose the possibility that the effectiveness of species of Aphidiinae as biological control agents is influenced by differences in the duration of aphid reproduction following parasitization.

Banker-plant systems with Aphidius species have been used to control pest aphids in greenhouses in Japan. However, the occurrence of secondary parasitoids, which lead to aphid-control failures, and of minor aphid species, are problematic. In this work the ecological characteristics of Ephedrus nacheri Quilis (Hymenoptera: Braconidae), an alternative biological control agent to Aphidius species against the pest aphids Aphis gossypii and Myzus persicae, were examined under laboratory conditions at 25 °C. Attack rate, success of parasitization, and offspring sex ratio were highly dependent on aphid species and instar stage. Development time and offspring body size depended on aphid species. Because of insufficient honeydew production, survival of the female wasp decreased when the host density was low; as a result, a type III functional response curve was observed for the two aphid species in most stage combinations. The intrinsic rate of natural increase estimated by use of the bootstrap method ranged from 0.128 to 0.258, depending on the larval mortality, host species, and stage. These values were insufficient to support inoculative use of E. nacheri for aphid control. In future work we will conduct a survey to discover a better combination of banker plant and host aphid which maintains a sufficient population and offspring sex-ratio, and decide the scale of the banker-plant system in the greenhouse that will supply a sufficient wasp population.

Development of resistant cultivars has been an effective method for controlling rice blast disease caused by Magnaporthe oryzae. Quantitative blast resistance genes may offer durable resistance because the selection pressure on M. oryzae to overcome resistance is low as a result of the genes’ moderate susceptibility. Because the effects of individual resistance genes are relatively small, pyramiding these genes in rice cultivars is a promising strategy. Here, we used near-isogenic and backcross lines of rice cultivar Koshihikari with single- or two-gene combinations of blast resistance genes (pi21, Pi34, and Pi35) to evaluate the suppression of leaf blast. The severity of the disease was assessed throughout the infection process. Resistance varied among the lines: Pi35 conferred the strongest resistance, while Pi34 showed the weakest effects. Two types of combined-gene interactions were observed, and they varied on the basis of gene combination and characteristic of the infection: (i) the combination of two resistance genes was more effective than either of the genes individually or (ii) the combination of two resistance genes was similar to the level of the most effective resistance gene in the pair. The most effective gene combination for the suppression of leaf blast was pi21 + Pi35.

Many parasitoid wasps are highly specialized in nature, attacking only one or a few species of hosts. Host range is often determined by a range of biological and ecological characteristics of the host including diet, growth potential, immunity, and phylogeny. The solitary koinobiont endoparasitoid wasp, Cotesia vestalis , mainly parasitizes diamondback moth (DBM) larvae in the field, although it has been reported that to possess a relatively wide lepidopteran host range. To better understand the biology of C vestalis as a potential biological control of hosts other than the DBM, it is necessary to determine suitability for potential hosts. In this study, the potential host range of the wasp and its developmental capacity in each host larva were examined under laboratory conditions using 27 lepidopteran species from 10 families. The wasp was able to parasitize 15 of the 27 species successfully. Some host species were not able to exclude C vestalis via their internal physiological defenses. When parasitization was unsuccessful, most hosts killed the parasitoid at the egg stage or early first-instar stage using encapsulation, but some host species disturbed the development of the parasitoid at various stages. No phylogenetic relationships were found among suitable and unsuitable hosts, revealing that host range in some endoparasitoids is not constrained by relatedness among hosts based on immunity.

The limited availability of sugar sources (e.g., flowers) in greenhouses may affect biological pest control by parasitoid wasps. However, few studies have focused on feeding devices to provide parasitoids with sugar foods. We investigated the accessibility of a yellow-colored bottle-type feeding device to adult Cotesia vestalis (Halliday), a larval endoparasitoid of the diamondback moth Plutella xylostella (L.). All parasitoids died within four days in a room with no sugar source, whereas 66.7 % of individuals survived if a bottle-type feeding device providing honey solution was installed. We also investigated female longevity in response to different sugar solutions presented in a bottle-type feeding device. Honey and sugar mixtures (glucose and fructose) improved female longevity (38.4 and 39.2 days, respectively) much more than water (3.1 days), indicating these feeding devices containing sugar foods to be potentially useful for maintaining C. vestalis in greenhouses where natural food sources are limited.

Banker-plant systems using Aphidius species have been employed to control pest aphids in greenhouses growing eggplant and sweet pepper in Japan. However, a strong negative correlation between the occurrence of secondary parasitoids and aphid-control success by this system was reported by Nagasaka et al. (2010). To control secondary parasitoid populations, detailed knowledge of their ecological characteristics is needed. In this paper, the development and parasitization ability of Dendrocerus laticeps (Hedicke) (Hymenoptera: Megaspilidae), a major secondary ectoparasitoid of Aphidius species in Japan, were examined under 25 °C laboratory conditions. The maximum female longevity was about 11 days when honeydew was available. Parasitization occurred only on mummified aphids, and the age of mummified aphids did not influence the ecological value of offspring. The maximum parasitization ability was 18.9 hosts/day estimated by Holling’s disc equation. Possible lifetime fecundity was 100.35. The intrinsic rate of natural increase estimated by the bootstrap method ranged from 0.211 to 0.321, depending on the assumptions made about larval mortality. The countermeasures for avoiding the negative impacts of D. laticeps in a banker-plant system include the development of a refuge for mummified aphids and increasing the temperature around the banker plants.

Evaluation of the landscape-level movement of Stenotus rubrovittatus (Matsumura), a major rice pest in Japan, is essential for establishing management strategies. We assessed the immigration timing and the average dispersal distance from a bank slope covered with Italian ryegrass Lolium multiflorum Lam. to paddy fields by periodic sampling in two regions in Chiba Prefecture. The immigrant densities in paddy fields increased exponentially as they approached the bank slope as a large-scale habitat of the insect. The relationship between immigrant density and distance from the source habitat fit an empirical model and theoretical model well. The theoretical model estimated the average dispersal distance during immigration: that of females was 72.0 and 92.1 m and that of males was 122.0 and 112.9 m in the respective regions. In addition, the average dispersal distance of males increased 7 days or later after the rice heading date despite the steady dispersal distance of females.

An effective means of supplying food to Cotesia vestalis, the larval endoparasitoid of the diamondback moth, Plutella xylostella, was examined in a laboratory and an experimental small greenhouse. Compared to the red and blue boards, yellow boards significantly attracted parasitoids in the laboratory and in the small greenhouse, the yellow feeding site was more effectively utilized by parasitoids than the white one. The parasitoid tended to utilize a feeding site hung 50 cm above ground more than one hung 200 cm above ground, hence we concluded that color and height were important factors for the recognition of the feeding sites by C. vestalis.

Two rice bug species, Stenotus rubrovittatus (Matsumura) and Trigonotylus caelestialium (Kirkaldy) (Hemiptera: Miridae), are major rice pests in Japan. The populations of these insects are maintained by widely distributed host plants and by a broad range of movements among resource patches. To develop an effective pest management strategy for a region where two rice bug species coexist, the impacts of the surrounding landscape and of weed-infested field boundaries on the field abundances of the two rice bug species were compared. Field abundances of the two species were estimated using the sweep-netting technique. The number of weed-infested field boundaries was also counted within a 100 m radius around 14 study paddies at three sites in Japan. The distinctive features of the surrounding landscape furnished the best predictor at a spatial scale radius of 300 m for S. rubrovittatus and at 200–300 m for T. caelestialium. The abundances of both species increased as the amounts of weed-infested area and reclaimed land increased. The size and number of sources also affected the two rice bug species. These results emphasize that adequate field boundary management can reduce the risk of high pest abundance in the fields, even when an extensive weed-infested area exists within the functional scale of the species.

特に盛暑期での利用を想定したショクガタマバエ等のアブラムシ捕食性天敵を用いたバンカー法の代替餌としての有用性を評価するため，ソルガムあるいはオオムギを餌として飼育した4種のアブラムシ，トウモロコシアブラムシ，ヒエノアブラムシ，ムギクビレアブラムシ，ムギミドリアブラムシの内的自然増加率を比較した．15℃，20℃，25℃，30℃の4種恒温条件下において2種の寄主植物の葉片上で飼育した各アブラムシの生存曲線，全生存期間，生涯産仔数を調査し，これらをもとに内的自然増加率を算出した．ソルガムの葉片で飼育した場合，すべての温度条件下で4種のうちヒエノアブラムシの内的自然増加率が最も高かった．オオムギの葉片で飼育した場合，20℃，25℃，30℃の条件下でムギミドリアブラムシの内的自然増加率が最も高かった．以上のデータから，バンカー植物としてソルガム，代替餌としてヒエノアブラムシの組み合わせが盛暑期に利用するバンカー法に適していると考えられた．得られた結果に基づき，施設栽培でのこれらのバンカー植物，代替餌の有効性を考察した．

The relationship between larval instar and head-capsule width in Helicoverpa armigera (Hubner) was examined in laboratory-reared and field-collected insects from Ibaraki and Yamanashi in eastern Japan. Each of the first three and each of the last three instars could reliably be distinguished using head-capsule width for both strains fed on an artificial diet. In the laboratory, 91.8% of larvae from Ibaraki had five instars, and 8.2% had six or seven instars, while 36.1% of the larvae from Yamanashi had five instars, and the rest had six instars. Pupation occurred when the larval head-capsule width reached about 2.6 mm, and the development time for each instar was independent of the total number of instars. Consequently, head-capsules were typically larger at each instar for larvae with fewer instars. The distribution of head-capsule widths in larvae obtained from sunflowers in Ibaraki showed peaks corresponding to the first, penultimate, and ultimate instars of laboratory-reared larvae. However, the widths supposedly representing the second and third instars were smaller than those found in the laboratory, suggesting that H. armigera larvae molt more times in the field than in the laboratory and require a longer time to complete development on sunflowers. These results may enable improvement of H. armigera forecasting and insecticide bioassay tests.

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.

Japan has only three registered baculovirus biopesticides despite its long history of studies on insect viruses. High production cost is one of the main hindrances for practical use of baculoviruses. Enhancement of insecticidal effect is one possible way to overcome this problem, so there have been many attempts to develop additives for baculoviruses. We found that alkaline soluble proteins of capsules (GVPs) of Xestia c-nigrum granulovirus can increase infectivity of some viruses including Mamestra brassicae nucleopolyhedrovirus (MabrNPV), and previously reported that MabrNPV mixed with GVPs was highly infectious to three important noctuid pests of vegetables in the following order, Helicoverpa armigera, M. brassicae, and Autographa nigrisigna. In this study, small-plot experiments were performed to assess concentrations of MabrNPV and GVPs at three cabbage fields and a broccoli field for the control of M. brassicae. In the first experiment, addition of GVPs (10 µg/mL) to MabrNPV at 106 OBs/mL resulted in a significant increase in NPV infection (from 53% to 66%). In the second experiment, the enhancing effect of GVP on NPV infection was confirmed at 10-times lower concentrations of MabrNPV. In the third and fourth experiments, a 50% reduction in GVPs (from 10 µg/mL to 5 µg/mL) did not result in a lowering of infectivity of the formulations containing MabrNPV at 105 OBs/mL. These results indicate that GVPs are promising additives for virus insecticides.

To study the potential competitive risk of the introduced Chrysoperla carnea (Stephens) on the indigenous trash-carrying chrysopid Mallada desjardinsi (Navas), we studied the occurrence of cannibalism and intraguild predation (IGP) at different prey densities. In C. carnea, 100% cannibalism was observed in the absence of aphids. In M. desjardinsi, cannibalism was also observed, but absence of cannibalism occurred at 35% in pairs of second- + third-instar larvae and at 70% in pairs of third- + third-instar larvae. In pairs of M. desjardinsi larvae whose trash package had been artificially removed, all third-instar larvae ate second-instar larvae. The trash package may play a role in the reduced mortality of younger larvae by cannibalism. IGP occurred in all pairs. In the absence of aphids, the interaction was symmetric between second-instar larvae, but asymmetric for second- versus third- and third- versus third-instar larvae, and the interaction was similar when M. desjardinsi larvae with or with...

The influence of food supply on the parasitoid Cotesia plutellae regarding the survival and reproductive potential of a non-target pest, pea leafminer Chromatomyia horticola, was examined in the laboratory. The male longevity of the leafminer dramatically increased when sugar or honey was available. On the other hand, sugar- or honey-fed females lived shorter lives than those fed on the host plant. Lifetime copulation times of the males were increased by their food supply. The lifetime fecundity of a pair significantly increased sugar or honey was supplied. This phenomenon was mainly explained by the positive relationship between the fecundity and the copulation count of females. We discuss the risk of an additional food supply increasing the numbers of non-target pests.

We report on laboratory hybridization between the indigenous Chrysoperla nipponensis and its close relative, C. carnea, which has been imported since 2001 from Germany to Japan as a biological control agent. Interspecific hybrids were obtained, and fully viable and fertile F1 and F2 generations were produced. Crosses between C. carnea females and C. nipponensis males showed 41.3% fertility, but the reciprocal cross showed only 9.5% fertility. Despite the low fertility of interspecific crosses, most F1 hybrids were fertile and were successfully backcrossed to both parental species. However, F1 males from C. carnea females × C. nipponensis males showed low fertility (zero except for 20% in one case) when crossed with any females (F1 or backcross). In the one combination resulting in 20% fertility, an extremely long preoviposition period was observed, caused presumably by a mating delay. The absence of change in hatchability, adult emergence rate, total developmental period, or deviation from the 50...

The influence of food supply on the survival and oviposition ability of Cotesia plutellae, the larval parasitoid of the diamondback moth, Plutella xylostella, was examined in the laboratory. The longevity of the parasitoid decreased drastically under a lack of sugar availability. The oviposition ability, evaluated by functional response to host density, was highly suppressed by a lack of food supply. Thus, sugar availability is a very important condition for the effective utilization of C. plutellae as a biological control agent of P. xylostella in greenhouses.

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

In order to find alternative diets for Amblyseius cucumeris, eleven pollen species and three high protein powders were tested. Females laid numerous eggs when fed on pollen from tea, craple myrtle, fragrant olive, persimmon and Japanese pear, but few eggs on pollen from chrysanthemum, tall goldenrod, Asiatic lily, cistus and orange. They also laid few eggs when fed on soybean flour, casein powder and defatted Deccan glass powder. Survival rates on the first five pollen species were not significantly different from the mold mite controls, indicating these pollen species are suitable as food sources. A. cucumeris showed an escaping behavior to pollen of Lycoris radiata and died within 4 days. Toxic compounds may be contained in pollen of this species. There was no correlation between pollen size and oviposition rates. Suitability of pollen species as a diet appears to be related to taxa of the plants.

Among many stabilizing factors for community dynamics, nonlinear biological interactions such as type III functional response have been widely considered to be major characteristics. However, most experimental biological communities employed so far had quite simple structures. Therefore, the possibility that the conclusions in earlier studies were dependent on simple community structure is undeniable. In this study, using a multiple-species experimental community, we evaluated which combinations of component species and what kinds of interspecific interactions allow communities to persist and how these contribute to community persistence. We conducted experimental communities using two species of beans, the adzuki bean (Vigna angularis) and the red kidney bean (Phaseolus vulgaris), two species of bean weevils, the Mexican bean weevil (Zabrotes subfasciatus, Coleoptera: Bruchidae) and adzuki bean weevil (Callosobruchus chinensis, Coleoptera: Bruchidae), and two species of parasitic wasp, Heterospilus prosopidis (Hymenoptera: Braconidae) and Anisopteromalus calandrae (Hymenoptera: Pteromalidae). The outcome of multiple-generation experimental communities was explained by the characteristics of component species obtained from short-term experiments. In our two resources–two herbivores–one carnivore system, the strong density-dependent attack ability of one parasitic wasp species (A. calandrae) led to the extinction of C. chinensis. On the other hand, the weak density-dependent attack ability of the other parasitic wasp species (H. prosopidis) led to system persistence. Our overall results show that, in a multiple-species community, the combination of species itself is more important for community persistence than are the characteristics of the particular species.

Among many stabilizing factors for community dynamics, spatial and temporal heterogeneities have been widely considered in recent years as two of the most important properties. However, the difference between the two types of heterogeneities have not been studied, except for Clark and Yoshimura (1993). We evaluated experimentally the effect of temporal and spatial heterogeneities on the persistence of a biological community. The experimental communities consisted of one parasitic wasp species, one bean weevil species, and two kinds of bean. Temporal and spatial heterogeneities of experimental communities were generated by kinds and timing of bean supply. Of all the experimental communities, the most persistent community was a temporally and spatially homogeneous community with Red Kidney bean as primary resource. Compared to spatially heterogeneous communities, temporally heterogeneous communities were more persistent. These results were easily explained by considering the attack rate of parasitic wasps and the difference between arithmetic and geometric means. In order to discuss the relative importance of environmental heterogeneity and the mode of biological interaction on community persistence, we have to measure the degree of environmental heterogeneity as the rate of change of the strength of interspecific interactions.

Many parasitoid wasps are highly specialized in nature, attacking only one or a few species of hosts. Host range is often determined by a range of biological and ecological characteristics of the host including diet, growth potential, immunity, and phylogeny. The solitary koinobiont endoparasitoid wasp, Cotesia vestalis, mainly parasitizes diamondback moth (DBM) larvae in the field, although it has been reported that to possess a relatively wide lepidopteran host range. To better understand the biology of C vestalis as a potential biological control of hosts other than the DBM, it is necessary to determine suitability for potential hosts. In this study, the potential host range of the wasp and its developmental capacity in each host larva were examined under laboratory conditions using 27 lepidopteran species from 10 families. The wasp was able to parasitize 15 of the 27 species successfully. Some host species were not able to exclude C vestalis via their internal physiological defenses. When parasitization was unsuccessful, most hosts killed the parasitoid at the egg stage or early first-instar stage using encapsulation, but some host species disturbed the development of the parasitoid at various stages. No phylogenetic relationships were found among suitable and unsuitable hosts, revealing that host range in some endoparasitoids is not constrained by relatedness among hosts based on immunity.

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