Applied Entomology and Zoology最新文献

Entoria okinawaensis Shiraki, 1935 (Phasmatodea: Phasmatidae) is a stick insect originally distributed among the subtropical islands of Japan. This species, after introduction into the southernmost regions of Kyushu Island, became established there. After insects were collected for this study from Ibusuki city, Kagoshima prefecture, Japan, their eggs were used for experimentation. Embryonic development was fundamentally temperature dependent. At 25 °C, many eggs hatched approximately 2 months after oviposition. However, hatching was observed continuously until the end of the 240-day experiment. Findings from egg dissection suggest that a small number of eggs arrest development at the early embryonic stages. Fluorescence observation of DAPI-stained eggs reveals that eggs show arrested development at the very attenuated blastoderm period. This study proves the existence of embryonic diapause in E. okinawaensis, although the incidence of diapause eggs is small. If future changes in the incidence and duration of diapause as adaptations to local climate occur, then the domestic-introduced subtropical stick insect might expand its distribution range farther north.

The challenge of dengue control due to the unavailability of a specific medication stresses the importance of releasing Wolbachia-carrying mosquitoes through vector control programs. This study investigated the sustainability and frequency of Wolbachia in Wolbachia-dengue-carrying mosquitoes in two dengue hotspot localities in Selangor. A modified sticky ovitrap was used to collect adult mosquitoes in two Wolbachia-releasing areas in Selangor, Kelana Puteri and Kelana D'Putera condominiums. All mosquito samples were subjected to PCR using wsp-specific primers for Wolbachia detection. Dengue virus was detected using RT-PCR, followed by multiplex-PCR. Out of the 80 Aedes spp. collected, Ae. aegypti was the most predominant species. More than one-third of Ae. aegypti were positive for Wolbachia, with 22.9% being superinfected with both Wolbachia A and B strains. About 61.4% of the species were uninfected with Wolbachia. Ae. aegypti carrying the Wolbachia A strain was also identified, which has previously never been reported. This strain was similar to the one found naturally in Ae. albopictus. None of the Ae. aegypti and Ae. albopictus were positive for dengue virus. This study could serve as a model for local researchers or health authorities to design and plan an effective field release and monitoring of Wolbachia-infected mosquitoes.

The sterile insect technique (SIT) is a pest control method that releases a large number of sterile pests into the field to inhibit mating between wild pests, ultimately resulting in the eradication of wild pest populations. It has often been discussed whether releasing one sex (mainly males) of sterile insects enhances the pest control efficiency of SIT compared to releasing both sexes (bisexual release). The control efficiency of sterile females may be negatively affected by their release, because sterile males lose the opportunity to mate with wild females. In this study, we investigated whether sterile females have a positive effect on the control efficiency of SIT and whether there is an additive or synergistic effect of releasing both sexes using two weevil species, Cylas formicarius and Euscepes postfasciatus, which are serious pests of the sweet potato Ipomoea batatas and targets of SIT in Okinawa. The results showed that in both species, the reproduction rate of wild pests was significantly suppressed in the case of the sterile female-only release. Interestingly, the most effective method varied between male-only and bisexual release depending on the density of sterile individuals and weevil species. Synergistic effects of both sexes on bisexual release were observed but varied with the density of sterile individuals and weevil species. High-density bisexual release was most effective for the SIT of at least two weevil species.

Subterranean termites primarily use decaying wood as both nest material and food, and the worker caste is responsible for searching for new wood. Because brown-rotted wood contains (Z,Z,E)-3,6,8-dodecatrien-1-ol, which is a trail pheromone component in Reticulitermes termites, it is considered that this compound attracts termite workers. However, while the trail pheromone allows passing workers to continue to move along it, it is unlikely to attract them from a distance. Therefore, workers should use other attractants derived from decaying wood as cues to locate it. In this study, we found that an aromatic abietane diterpenoid in termite culture medium made from brown-rotted Japanese red pine (Pinus densiflora) attracted workers of the Japanese subterranean termite Reticulitermes speratus (Kolbe) (Isoptera: Rhinotermitidae). Gas chromatography analyses and behavioral assays revealed that the n-hexane extract of the medium contains dehydroabietic acid, which is a resin component of various conifers, and this compound attracts workers. These results strongly suggest that R. speratus workers mainly use this compound as a cue to locate brown-rotted pinewood in nature. Our study contributes to the understanding of the mechanisms of wood detection in termites.

Diversifying crop habitats and controlling arthropod pests by cultivating “secondary plants” alongside a primary crop is a frequently discussed strategy. The effectiveness of using secondary plants to manage pests varies across countries, and is influenced by factors such as the target pest, plant species, experimental design, and climatic conditions. Consequently, we conducted a study investing the impact of intercropping wheat or barley with additional flower strips on controlling aphid pests in white cabbage fields in Japan and Germany.Query Our results in Japan supported the natural enemies hypothesis, leading to a significant reduction in populations of two pest aphids: the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), and the cabbage aphid, Brevicoryne brassicae (L.) (Hemiptera: Aphididae). Furthermore, intercropping and/or flower strips increased the proportions of natural enemies, including hoverfly larvae (Diptera: Syrphidae), ladybirds (Coccinellidae: Coleoptera), and parasitoid wasps (Hymenoptera: Braconidae), relative to the aphids. Hoverfly larvae, due to their high abundance, appeared to be Japan’s most effective aphid suppressors. In contrast, in Germany, intercropping and flower strips did not remarkably suppress aphid populations or enhance the presence of the natural enemies, despite a temporary increase in the population density of hoverfly larvae in intercropping. These disparities between the trials in the two countries may be attributed to variations in regional and local biodiversity. This suggests that using secondary plants for pest control should consider the specificities of local environments.

Sexual selection is a driving force behind the evolution of insect genitalia morphology. Understanding the functional morphologies of mating-related structures can help explain the evolution of diverse genital morphologies. However, this research is limited to many insect groups, such as the Cerambycidae. We observed the mating process and morphology of mating-related structures of the longhorn beetle Dorysthenes granulosus (Thomson) (Coleoptera: Cerambycidae: Prioninae). Our observations revealed mating behavior characteristics and the functional morphology of genitalia and leg tarsi. The mating process of D. granulosus can be divided into three stages: mounting, insemination, and guarding. The male usually spends 30 min from mounting to control the female, then extends its endophallus and typically inserts it twice into the female reproductive tract. Each insertion lasts for about 40 s. After that, the male begins a long-time insemination, which lasts for two to three minutes. Then, the male withdraws the endophallus and the female reproductive tract secretes a sperm mass. After insemination, some males continue to mount the female for a postcopulatory guarding period, which can last from one to five hours. During copulation, barbs on the surface of the everted male endophallus directly contact the female reproductive tract. The male fore and mid leg tarsi firmly grasp the female elytra, thorax, and abdomen. We discuss the functional morphologies of mating-related structures and the possible reason for male multiple insertions in the Cerambycidae.

Although Trichogramma principium (Sugonjaev & Sorokina) (Hymenoptera: Trichogrammatidae) is an effective natural enemy in agricultural ecosystems, its tri-trophic interactions should be investigated in more detail. In the present study, life table parameters of the parasitoid wasp and its population projection were investigated under controlled conditions (25 ± 1 °C, 60 ± 5% RH, and 16:8 h L:D) on Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). The herbivore was reared using three different cultivars, including Early Urbana, Super Strain-B, and Primo Early, as well as being treated with four nitrogen levels (0, 2100, 3000, and 3900 ppm). Data analysis was performed based on an age-stage two-sex life table by linking the life table parameters and population projection. Results indicated a significant increase in net reproductive rate (R₀) and intrinsic rate (r). Therefore, the fertilized treatments were relatively favorable hosts for the herbivore and consequently for the parasitoid wasps than unfertilized treatments. Population projection results also indicated differences in the stage population growth rate, age-staged population fluctuations and the parasitism capacity of the parasitoid. These findings indicated that linking life table and population projection is an appropriate method for clarifying the precise timing and the successful release of natural enemies.

The brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) and the green rice leafhopper, Nephotettix cincticeps Uhler (Hemiptera: Cicadellidae) feed by sucking phloem sap from rice plants and excreting honeydew containing glucose. It is known that there are resistant rice cultivars against Ni. lugens or Ne. cincticeps, from which insects are unable to suck phloem sap. Here, we developed a simple method using a glucometer to measure glucose concentration in honeydew and use it to evaluate rice resistance against sucking insects. In case of Ni. lugens, the honeydew excreted by sucking a susceptible rice line was large in volume and glucose content. In contrast, the honeydew excreted by sucking a resistant rice line was low in volume and glucose content. In case of Ne. cincticeps, no glucose was detected in the honeydew excreted by sucking a resistant rice line, although more honeydew was excreted from the resistant rice line than the susceptible rice line. Therefore, it was suggested that Ne. cincticeps could not suck phloem sap of the resistant cultivar. Glucose analysis of honeydew using a glucometer would be useful for evaluating sucking inhibition of rice cultivars against Ni. lugens and Ne. cincticeps.

Real-time quantitative polymerase chain reaction (qPCR) is used to estimate the population densities of the potato cyst nematodes Globodera pallida Stone and Globodera rostochiensis (Wollenweber) Skarbilovich (Tylenchida: Heteroderidae). Since it is difficult to extract nematode DNA from large amounts of soil (≥ 100 g, enough for quantification of cyst nematodes), cyst isolation is required before DNA extraction. However, when isolating cysts from the soil, various impurities are simultaneously isolated, and separating the cysts from these impurities is laborious. Although previous studies have reported methods for extracting DNA from mixtures of cysts and impurities, it is unclear whether such DNA can be used to estimate nematode densities using qPCR. To examine the effects of impurities on the accuracy of qPCR quantification, we extracted DNA from nematode eggs (G. pallida and G. rostochiensis) mixed with impurities and performed qPCR. The results suggested that the differences in the fields affected the quantification accuracy. Therefore, field-specific standard curves should be set, which are impractical for routine diagnosis. To propose a more practical method, we determined a fixed standard curve for each species and estimated the population densities in field soil samples by qPCR using the standard curves. The estimated population densities significantly correlated with those determined using conventional microscopic inspections. This study revealed that the population densities of G. pallida and G. rostochiensis can be estimated from large amounts of soil, probably only approximately, but efficiently, by qPCR using DNA extracted from mixtures of cysts and impurities.

The West Indian sweetpotato weevil, Euscepes postfasciatus, a serious pest of sweet potatoes, is being eradicated by sterile insect technique (SIT) in the south-western islands of Japan. Information on the diurnal movement of the target pests on host plants and where mating and egg-laying behavior occurs on the host is important for the application of SIT, which eradicates the target pest through mating of released sterile males and wild females. However, little such information is available on this species. In this study, male and female adults were released on host plants to examine the diurnal distribution on seedlings according to sex, as well as the sites where mounting behavior and egg laying occurs. The results showed that females left the host plant more frequently at night, whereas males were more likely to remain on the host plant at night. Both males and females stayed on the nodes of the host plant during the daytime. Mounting behavior also tended to occur more often at nodes. Furthermore, compared to unmated females, mated females stayed at the vertical top of the seedlings. However, it was found that eggs were often laid close to the roots rather than at the top of the vertical stems, even when the seedlings were placed upside down. The results of previous studies and this study will be discussed from the perspective of the application of SIT against E. postfasciatus.