The silkworm, Bombyx mori (Linnaeus) (Lepidoptera: Bombycidae), is widely utilized for silk production and is recognized for its high protein expression capacity. Genomic resources and gene models established using the p50ma strain have been invaluable for genetic, physiological, and recombinant protein research. The silkworm–baculovirus expression system, particularly effective in the f38 strain, holds significant potential for large-scale protein production and can be further optimized by genome editing and genetic engineering. The availability of non-diapause eggs is essential for microinjection-based genome editing and transgenesis. However, conventional induction of non-diapause eggs by low temperature and constant darkness incubation is time-consuming and can be strain dependent. In this study, we successfully generated non-diapause strains by knocking out the diapause hormone receptor 1 gene (DHR) using the CRISPR/Cas9 system. The resulting non-diapause f38 and p50ma strains were suitable for microinjection and provided a stable platform for genetic and physiological studies. We further validated the utility of the established non-diapause strains for genome engineering by knocking out the sex-specific storage protein 1 gene (SP1) and confirming loss of the corresponding protein by SDS‑PAGE. These findings demonstrate that targeted disruption of DHR enables the establishment of non-diapause silkworm strains, thereby enhancing their utility in diverse research and biotechnological applications.
Host-associated microbial communities play a central role in insect ecology and evolution, yet comparative studies across diverse taxa remain limited for many taxa and regions. Here, we conducted a multi-species survey of whole-bacterial communities associated with 17 Pentatomomorpha (Hemiptera) species from four families (Pentatomidae, Coreidae, Lygaeidae, Pyrrhocoridae) collected from natural populations in France, using 16S rRNA gene sequencing. Microbiota composition differed markedly among host families: mostbacterial communites hosted by Pentatomoidae species were dominated by members of the Pantoea/Erwinia genera, consistent with their putative role as obligate nutritional symbionts. In contrast, Pyrrhocoridae, Coreidae, and Lygaeidae harbored more diverse bacterial communities, including Sphingobium, Hungatella, and Gordonibacter. Serratia was frequently detected and often highly prevalent across species and sites, suggesting it may be a widespread facultative symbiont in Pentatomomorpha in Western Europe. Host taxonomy was a major determinant of microbiota diversity and composition, with a significant signal of phylosymbiosis, indicating that evolutionary history shapes microbiome assembly, while ecological factors such as diet, physiology, and environmental exposure further influence community structure. Network analyses revealed interspecific differences in bacterial community organization, with several low-abundance taxa occupying central positions within microbial interaction networks. By contrast, transovarially inherited endosymbionts, such as Wolbachia and Spiroplasma, were rare accross sample species. This study establishes a baseline for Pentatomomorpha microbiota, highlights the joint influence of host evolution and ecology on microbial communities, and provides a foundation for microbiome-based approaches to sustainable pest management.
Rice planthoppers are economically important pests of rice in Asia. Among the rice planthopper species, Nilaparvata lugens (Stål) and Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) are unable to overwinter successfully in temperate areas of East Asia, including Japan, but re-colonize these areas annually following long-distance migration from southern overwintering areas. Because the invasion of N. lugens and S. furcifera into paddy fields is greatly influenced by the timing and magnitude of their migrations, which vary from year to year, it is important to efficiently monitor their invasion in each paddy field for effective management. In this study, we evaluated the suitability of the yellow sticky trap method, which can be used for monitoring flying insect pests in the field, to monitor N. lugens and S. furcifera, in paddy fields in Japan. We found that the yellow sticky trap method detected the invasion of N. lugens and S. furcifera in paddy fields earlier than the standard sticky board method, one of the most common and effective monitoring methods for them in paddy fields. Our results indicate that the yellow sticky trap method is suitable for detecting N. lugens and S. furcifera at the beginning of invasion in paddy fields in temperate areas of East Asia. In addition, our study indicates that the yellow sticky trap method is likely unsuitable for accurately monitoring the seasonal occurrence of N. lugens and S. furcifera in paddy fields, at least in its current form.
Predatory cecidomyiids of the genus Diadiplosis Felt, 1911 (Diptera: Cecidomyiidae) are widely distributed throughout the Neotropical Region. Of the 34 species currently known in the genus, 14 have been recorded from Central and South America, making it, thus far, the genus of predatory cecidomyiids with the highest number of species recorded in this region. This study consolidates recent findings on the diversity of this genus in Brazil and provides detailed morphological information on its immature forms. We describe and illustrate the larva, pupa, male, and female of two new predatory cecidomyiid species, Diadiplosis duriganae sp. nov. and D. carmonetoi sp. nov., associated with mealybugs (Hemiptera: Pseudococcidae) collected from agricultural systems and the Cerrado biome (Brazilian savanna) in São Paulo State, Brazil. The new species are compared with their congeners, and an updated identification key for Neotropical male species is provided, along with diagnoses of the genus and each new species.
Occurrences of secondary parasitoids on five primary aphid parasitoids were surveyed using traps with parasitised aphids on potted plants in two field experiments to clarify their risk to banker-plant systems. In Field Experiment 1, from 2010 to 2012, three primary parasitoids, Aphidius gifuensis Ashmead, Diaeretiella rapae (M’Intosh), and Ephedrus nacheri Quilis (Hymenoptera: Braconidae: Aphidiinae), were prepared on Myzus persicae (Sulzer) (Hemiptera: Aphididae) on potted komatsuna plants or Rhopalosiphum maidis (Fitch) on potted barley or sorghum plants and exposed to the field for 7 days every 2 weeks from spring to autumn. In Field Experiment 2, in 2013, Aphidius colemani Viereck (Hymenoptera: Braconidae: Aphidiinae), E. nacheri, and Aphelinus varipes (Förster) (Hymenoptera: Aphelinidae) were prepared on M. persicae on potted komatsuna plants and exposed in the same manner. Mummified aphids were collected and emerged adults were identified. The following secondary parasitoids were identified: three species of Figitidae: Phaenoglyphis villosa (Hartig), Alloxysta victrix (Westwood), Alloxysta brevis (Thomson) group, one species of Encyrtidae: Syrphophagus tachikawai (Hoffer), two species of Megaspilidae: Dendrocerus laticeps (Hedicke) and Dendrocerus carpenteri (Curtis) and two species of Pteromalidae: Asaphes suspensus (Nees), and Pachyneuron aphidis (Bouché). Alloxysta victrix occurred on A. gifuensis and A. colemani, but was not detected on D. rapae, E. nacheri or A. varipes. Syrphophagus tachikawai occurred on A. gifuensis, A. colemani, D. rapae, and A. varipes in summer and autumn, but seldom appeared on E. nacheri. Pachyneuron aphidis primarily occurred in summer. This information will be useful for constructing banker-plant systems to avoid the risk from secondary parasitoids.
For this study, phytoseiid mite species composition was examined using quantitative sequencing (QS) at six Japanese pear orchards with different pesticide practices in 2024 and 2025. Results indicate Amblyseius eharai Amitai et Swirski (Acari: Phytoseiidae) as the most dominant species at study sites where commercialized Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) were introduced or where reduced use of chemical pesticides and fertilizers was conducted. By contrast, phytoseiid mites were rarely found or N. californicus was temporarily dominant at study sites for which conventional pesticide practices were applied. The proportion of sodium channel mutation (M918L) involved in pyrethroid resistance was also examined for phytoseiid mites using another QS. Results demonstrated that the resistant amino acid (L) was distributed in A. eharai and indigenous N. californicus. The spider mite survey, based on morphological characteristics, revealed Tetranychus urticae Koch (Acari: Tetranychidae) as present at study sites using conventional pesticide practices. At the other sites, Tetranychus kanzawai Kishida (Acari: Tetranychidae) infestation was observed in addition to that of T. urticae. Collectively, these results suggest that while pesticide practices are associated with the dominant species of phytoseiid mite and spider mite species in Japanese pear orchards, M918L is widespread among major indigenous phytoseiid mites, irrespective of pesticide practices.
Subterranean termite workers forage for and exploit decaying wood for new food resources while forming high-density groups. Recently, Mitaka et al. (2020) reported that a worker aggregation pheromone of the subterranean termite Reticulitermes speratus (Kolbe) (Isoptera: Heterotermitidae) consisted of six compounds, including 2-phenylundecane, n-pentacosane, n-heptacosane, palmitic acid, trans-vaccenic acid, and cholesterol. However, the previous study only used some colonies collected around Kyoto, Japan, leaving it unclear whether the pheromonal composition remains consistent across colonies in other regions of Japan. Also, it was unclear whether the components remain unchanged even when the workers eat different diets and which body part secretes the pheromone. In this study, using the R. speratus workers removed from colonies collected from various locations in the Tokai and Kinki regions, Japan, I compared the pheromone components among their workers fed on different diets. Gas chromatography-mass spectrometry (GC-MS) analysis and bioassays demonstrated that not all colonies have workers producing 2-phenylundecane and that workers can be attracted even by a blend of artificial aggregation pheromone without 2-phenylundecane. Furthermore, GC-MS analysis of extracts of workers’ footprint substances and various body parts revealed that n-pentacosane and n-heptacosane were present in both body surface and footprint substances and that palmitic acid, trans-vaccenic acid, and cholesterol were predicted to be secreted from the midgut or hindgut. These results suggest that the production of 2-phenylundecane depends on the colony backgrounds. This study provides insights into the relationship between food and pheromone production in termites.
Daphnephila gall midges (Diptera: Cecidomyiidae) inhabiting subtropical evergreen forests in Taiwan exhibit complex temporal diversification in their life histories. We conducted a 7-year field study (2004–2011) tracking four leaf-galling Daphnephila species on 105 Machilus thunbergii trees in northern Taiwan, integrating host phenology, gall development, adult emergence, and parasitism. The host tree displays bimodal bud flushing, producing winter and spring leaf cohorts that provide extended oviposition windows. Correspondingly, Daphnephila populations exhibit quadrimodal adult emergence generated by two forms of polymodality. Within a single generation, individuals display intraseasonal polymodality (Type A sensu Waldbauer 1978), emerging in both winter and spring. In addition, a proportion of larvae undergo extended diapause exceeding 1 year, corresponding to interannual polymodality (Type C). Offspring from the same female frequently diverged into univoltine and semivoltine pathways, demonstrating flexible life-history expression. Parasitism rates were significantly lower in winter-emergent individuals and in semivoltine cohorts, supporting enemy avoidance as a major driver of temporal diversification. This study represents the first explicit documentation of Type A polymodality in Cecidomyiidae and reveals a multi-layered bet-hedging strategy operating across seasonal and interannual scales in a subtropical gall-inducing insect system.
To improve the understanding of the taxonomy and host associations in the genus Gastrancistrus, we describe three new species, provide a key to Japanese species, and discuss previously undescribed morphological characters. In this research, Gastrancistrus aerugo Inoue Matsuo, sp. n., G. aquilus Inoue Matsuo sp. n., and G. yukawai Inoue Matsuo sp. n. (Hymenoptera: Pirenidae) are newly described from Japan. Gastrancistrus aerugo sp. n. is a parasitoid of an unidentified species of Cecidomyiidae (Diptera), which induces bud galls on Lonicera morrowii (Caprifoliaceae). Gastrancistrus aquilus sp. n. is a parasitoid of Peracecis yukawai (Diptera: Cecidomyiidae), which induces leaf galls on Celtis sinensis (Cannabaceae). Gastrancistrus yukawai sp. n. is a larval solitary endoparasitoid of Pseudasphondylia neolitseae (Diptera: Cecidomyiidae), which induces leaf galls on Neolitsea sericea (Lauraceae). Among these species, G. yukawai is morphologically similar to G. coxalis, which is redescribed in this paper because of the lack of morphological information. A key to Japanese Gastrancistrus species including two more Japanese species: G. fuscicornis and G. sugitama is provided. We also discuss the utility of using the previously undescribed variation in the depth and shape of the transpimeral sulcus and patterning of the lower mesepimeron in species identification.
Adults of tortoise beetles (Coleoptera: Chrysomelidae: Cassidinae) possess peculiar morphologies, such as explanate margins surrounding their body, tarsal pad for adhesion to the substrate, and long male genitalia that might be evolved via natural and sexual selection. Therefore, tortoise beetles are ideal materials for investigating the developmental mechanisms and evolution of many adaptive traits. This study attempts to evaluate the effectiveness of the RNA interference (RNAi) method for analyzing functions of genes related to the formation of adult morphologies using tortoise beetle species Thlaspida biramosa (Boheman) (Coleoptera: Chrysomelidae: Cassidinae). We inject dsRNA of the well-known appendage patterning gene, dachshund (dac), into the last-instar larvae of T. biramosa. dacRNAi adults exhibited a reduction in number of subsegments of antennae and legs as well as the formation of abnormal grooves on legs. Reduction of appendages has also been known in the previous studies using Drosophila and Tribolium when dac expression was suppressed, suggesting that the RNAi-based dac knockdown was likely to work successfully in T. biramosa. Additionally, this study reveals that the degree of abnormal phenotypes is the same between treatments with 0.1 and 1 µg of dac dsRNA, suggesting high RNAi potential in T. biramosa. Furthermore, there appears to be a specific dsRNA injection timing that maximized RNAi efficiency. Therefore, this study provides the first evidence of the potential for the RNAi-based gene silencing in tortoise beetles. Future studies will be able to analyze genes that cause the unique morphology of tortoise beetles by applying our larval RNAi method.
We studied long-term population dynamics of gall aphids and their host plants, manzanita shrubs (Ericaceae), at a field site along the Sierra–Cascade axis of northern California over a 20-year interval between wildfires. We sampled galls annually from a population of Arctostaphylos viscida (n = 133) and Arctostaphylos manzanita (n = 339) and dissected sample galls under a microscope to record the number of gall inducers (Tamalia coweni (Cockerell, 1905)) (Hemiptera: Aphididae) as well as inquilines (Tamalia inquilinus Miller, 2000) (Hemiptera: Aphididae) present in galls. We used a generalized linear mixed model to analyze insect counts per gall. Across the study period, the number of T. coweni apterous females per gall remained relatively constant. In contrast, apterous T. inquilinus females were more abundant (in galls containing both species) and exhibited pronounced temporal variability. These findings have potential implications for the rate and mode of evolutionary diversification in these two gall-dwelling aphid species.
Maternally inherited Wolbachia endosymbionts are known to manipulate arthropod reproduction. In the lepidopteran insect Eurema mandarina (de l’Orza 1869) (Lepidoptera: Pieridae), individuals doubly infected with a Wolbachia strain that induces cytoplasmic incompatibility, wCI, and a strain that induces feminization, wFem, have been reported from Tanegashima Island for at least 20 years. Feminization biases host population sex ratios toward females, potentially leading to extreme female-biased populations and the absence of males. However, how wFem and wFem-infected lineages are maintained over the long term remains an unresolved problem. Exploring an unstudied population with a sex ratio skewed by wFem can provide insights into the persistence mechanisms of wFem and its host. The present study aimed to elucidate the sex ratio and Wolbachia infection status of E. mandarina populations on Yakushima Island, located near Tanegashima Island in the southern part of Japan. Most individuals observed in the field were female, and PCR analyses based on the wsp gene showed that all females examined were doubly infected with wCI and wFem. A complete female bias was observed in offspring derived from these females, indicating that wFem induced feminization in butterflies. Mitochondrial DNA analyses revealed that E. mandarina populations from Yakushima and Tanegashima Islands shared the same mtDNA haplotypes, suggesting that the wFem-infected lineages on the two islands have a common maternal origin. Dissections of female individuals showed that females suffered a scarcity of males on Yakushima Island. The extreme sex ratio bias observed was considered especially severe in the E. mandarina population on Yakushima Island.
High level of host specificity is a strength in considering gall-inducing insects in weed biological-management campaigns. The effects of gall-inducing insects on plants are subtle and discreet and are rarely quantified to establish their value in biological management. The Tephritidae (Diptera), Curculionidae (Coleoptera), and some Lepidoptera are effective in regulating populations of herbaceous weeds, mainly because of their specialized level of host relations and the irreversible damage they inflict upon host plants by interrupting water and nutrient transport. By injuring the plant and by draining the nutrients, these insects inflict minor to moderate levels of stress in the tissues and organs they infest, in addition to strongly impacting plant-resource availability and allocation. The more-widely used Cecidomyiidae (Diptera) are relatively less efficient in inflicting plant damage, leading to plant death. Gall-inducing insects are parasitic organisms that utilise host tissues for nutrition and habitat; they rarely cause direct and widespread mortality in weeds. Rather, because of their strength as monophagous-plant feeders, they can be used as primary plant stressors to downgrade plant immunity levels and deplete resources that contribute to either maintaining or enhancing fitness. Target weeds most likely require additional stressors, such as plant–plant competition or introduction of a necrotrophic or a phytotoxin-producing fungus to deliver whole-plant death. We propose a novel framework, establishing the specific impacts of gall-inducing insects on plant-resource allocation, to permit future research to be more explicit about how gall-inducing insects can contribute to effective biological-management outcomes.
Brazil is among the world’s leading avocado producers, with cultivation increasingly threatened by gall-inducing midges that damage blossoms and impair fruit development. During surveys in commercial Hass avocado orchards in Minas Gerais, Brazil, a previously unknown species of Bruggmanniella Tavares, 1909 (Diptera: Cecidomyiidae) was discovered infesting young fruits. Here, we describe Bruggmanniella abacate sp. nov. Garcia and Urso, based on larvae, pupae, males, and females reared from malformed fruit galls. Larvae develop within the ovarian tissue, inducing elongated galls that lead to fruit abortion. This is the first record of a Bruggmanniella species associated with Persea americana Mill. cv. ‘Hass’ in Brazil. Our findings reveal previously undocumented diversity of avocado-infesting gall midges and underscore the need for further studies to evaluate their distribution, biology, and potential economic impact on the expanding Brazilian avocado production.
The Old World cecidomyiid genus Daphnephila is primarily associated with Machilus (Lauraceae) plants and exhibits exceptionally high gall diversity in Taiwan. At present, six described species correspond to only seven of 40 known Daphnephila gall morphospecies on the island. In this study, we clarified the species identities of Taiwanese Daphnephila inducing long ovoid-galls and ovoid-galls on the leaves of five Machilus plants, and explored their diversification using molecular evidence. Accordingly, two species, D. yukawai sp. n. and D. taiwanensis, were recognized based on morphological characteristics and species delimitation method (Assemble Species by Automatic Partitioning). The former species utilizes only the endemic M. mushaensis, primarily inducing ovoid-galls along the major leaf vein, whereas the latter species associates with five Machilus species and induces two gall types on various leaf parts. Notably, when sympatric with D. yukawai sp. n., D. taiwanensis exhibits character displacement of galling habit, forming long ovoid-galls along the minor leaf veins. Furthermore, the COI-based IQ tree supported: (1) a single origin of East Asian ovoid-gall Daphnephila species, (2) the sister-group relationship between the Taiwanese lineage and a Chinese species, and (3) the role of M. mushaensis as the probable ancestral host of the Taiwanese lineage, including D. taiwanensis. These results suggest that D. taiwanensis colonized additional Machilus hosts after diverging from D. yukawai sp. n. Taken together, our findings indicate that novel plant associations and shifts in galling sites may have facilitated diversification in Daphnephila cecidomyiids, contributing to the remarkable richness of Daphnephila galls in Taiwan.
The Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae), is a globally invasive species that forms dense supercolonies and remains difficult to control, especially in complex environments, such as riverbanks and urban facilities. Hydrogel baits have emerged as cost-effective resources for managing invasive ants; however, most formulations depend on synthetic polymers. This study assessed the field efficacy of a biodegradable hydrogel bait composed of cellulose nanofiber (microfibrillated cellulose) with pyriprole as the active ingredient. Field trials were conducted at riverbank habitats and around urban facilities in Japan. At riverbank sites, area-wide application of hydrogel bait at 15 g/m2 reduced mean trap catches to < 1
Cucurbits are monoecious plants that rely on pollinators for successful fertilization. In Hokkaido, a major area for squash and pumpkin production, the naturalized bumblebee Bombus terrestris (L.) (Hymenoptera: Apidae) (Bt) has become widespread and now coexists with native species such as B. hypocrita sapporensis Cockerell (Hymenoptera: Apidae) (Bhs), a close relative of Bt. Although Bt has recently become the dominant pollinator in pumpkin fields, its pollination efficiency has not been compared with that of native bumblebees, even in these fields. In this study, we examined the pollination behavior of Bt and Bhs in Cucurbita pepo L. cv. Stripe pepo fields in a semi-rural area of Obihiro, Hokkaido, focusing on flower visitation, pollen loads, pollen deposition on stigmas, and subsequent fruit and seed production. Our results showed that the native bumblebee Bhs, whose numbers have already declined in the semi-rural area, exhibits pollination efficiency similar to, or possibly higher than, that of the naturalized Bt, and pollination patterns may differ between the two species. Because Bt could have a pollination ability comparable to that of Bhs, replacement of Bhs by Bt might not necessarily harm cucurbit production in eastern Hokkaido. However, managing Bt population density is increasingly important for conserving native ecosystems.
This study examined whether eggs within a single pod of Locusta migratoria Linnaeus (Orthoptera: Acrididae) develop at different rates under natural conditions and how synchronized hatching is achieved despite such variation. Laboratory observations indicated that females laid eggs 3–7 cm below the sand surface. When post-diapause eggs were buried in soil for 10 days in spring and then incubated at 30 °C, those that had been deposited at 3 cm hatched approximately 20 h earlier than those at 7 cm, although the mean soil temperatures did not differ significantly between depths. The greater thermal amplitude in the shallower layer is therefore likely to have accelerated development, suggesting that temperature fluctuations, rather than mean temperature alone, contribute to developmental differences among eggs in the field. Laboratory experiments confirmed that development under fluctuating-temperature regimes (20/25–35 °C) proceeded significantly faster than predicted by a linear degree-day model based on a threshold of 16.4 °C. This conclusion was further supported by another experiment in which daily degree-days were identical but the amplitude of temperature fluctuation differed. In addition, hatching synchrony markedly increased when eggs from 3 and 7 cm soil depths were kept in contact, providing direct evidence that embryo–embryo communication can synchronize hatching within a pod. These findings demonstrate that locust eggs experience distinct microthermal environments within their pods, respond developmentally to temperature fluctuations, and nevertheless achieve synchronous hatching through interembryonic signaling. Incorporating the effects of temperature fluctuations on development will improve the accuracy of developmental models under natural temperature variation.
A new gall-inducing species of Tanaostigmodes Ashmead, 1896 (Hymenoptera: Chalcidoidea: Tanaostigmatidae) is described from Handroanthus pulcherrimus (Bignoniaceae) in Buenos Aires Province, Argentina. The new species, Tanaostigmodes lapachosus sp. n., belongs to the emarginatus species group. Specimens were collected from galls on the midrib and petiolules of leaflets of H. pulcherrimus, a native tree widely distributed in northeastern Argentina, Paraguay, and Brazil, and commonly known as “lapacho amarillo misionero”. A survey conducted at the Arturo E. Ragonese Botanical Garden (INTA) revealed galls in 85
