Insect Science最新文献

Desiccant dusts have been shown to be effective materials in the management of bed bugs (Cimex spp.). Past research primarily focused on exploring the direct lethal effect of dusts against bed bugs, whereas information on their sublethal effects on bed bugs are limited. In this study, we evaluated the lethal effect of 3 dust products (Johnson's^® Baby powder, Vazor DE powder^™, and CimeXa™; abbreviated as Baby powder, DE, and CimeXa) against the tropical bed bug, Cimex hemipterus (F.), under laboratory conditions. Results showed that the 3 dust products caused 97%-100% mortality to tropical bed bugs within 14 d, both in no-choice and choice experiments. However, in a brief exposure experiment (crossing a 2.5-cm-wide band), Baby powder exposure caused a significantly lower mortality (23%) than DE (88%) and CimeXa (100%). The more effective dusts (DE and CimeXa) were selected for further evaluation of their sublethal effects on C. hemipterus. DE and CimeXa caused significantly higher mortality (48%-58%) through horizontal transfer than that of control (6%). Brief exposure to DE and CimeXa dusts did not affect tropical bed bug activity and their response to CO₂. However, CimeXa-exposed tropical bed bugs exhibited reduced feeding and lowered survival rate after feeding. Moreover, both DE and CimeXa dust bands showed strong barrier effects on the crawling of tropical bed bugs. Our results indicate that both DE and CimeXa have great potential for preventing C. hemipterus from reaching protected areas and for controlling C. hemipterus.

Our previous study shows that Coptotermes formosanus (Blattodea: Rhinotermitidae) preferred to stay on filter paper treated with ethyl 2,4-dioxovalerate, a metabolite in the soil fungus Trichoderma virens. Here, we hypothesized that adding ethyl 2,4-dioxovalerate in sand could trigger aggregation and tunneling preferences of C. formosanus and improve the effectiveness of liquid termiticide. In aggregation-choice tests, significantly more termites were found on/in sand blocks containing ethyl 2,4-dioxovalerate (250 µg/g) than untreated blocks throughout the 24-h experiments. In the tunneling-choice tests, termites also excavated significantly more tunnels in the sand treated with ethyl 2,4-dioxovalerate (2.5, 25, or 250 µg/g) than untreated sand. However, in no-choice tests, ethyl 2,4-dioxovalerate (2.5, 25, or 250 µg/g) did not significantly affect tunneling activities, termite survival, wood consumption, or activities of detoxification enzymes (peroxidase, superoxide dismutase, and catalase) compared to controls. Interestingly, in aggregation- and tunneling-choice tests, termites preferred to stay and made more tunnels in sand treated with both ethyl 2,4-dioxovalerate (250 µg/g) and fipronil (1 µg/g) than untreated sand. In addition, in choice tests, sand treated with the combination of ethyl 2,4-dioxovalerate (250 µg/g) and fipronil (1 µg/g) caused significantly higher termite mortality than the sand treated with only fipronil (1 µg/g). Our study showed that ethyl 2,4-dioxovalerate may enhance the effectiveness of fipronil (1 µg/g in sand) by triggering aggregation and tunneling preferences of termites, thereby increasing the contact between termites and fipronil.

Olfactory plays an important role in insect behaviors. Pheromone binding proteins (PBPs) are thought to play a certain role in the transport of pheromone molecules in the olfactory recognition process for courtship and mating. Mythimna separata is one of the most serious cereal pests in Asia. The sexual pheromone components of M. separata were clarified; however, to date, little evidence in vivo or in vitro has disclosed the binding properties of PBPs toward the pheromone components of M. separata. To address this research gap, the functional characterization of PBPs in M. separata, spectroscopic investigations were conducted by using recombinant MsepPBPs. Subsequently, MsepPBP1 and MsepPBP3 were selected for RNA interference to assess changes in behavioral responses of male mutants toward normal females. Fluorescence displacement binding assays, combined with fluorescence quenching assays, revealed that MsepPBP3, among the 3 MsepPBPs, exhibited the strongest affinity for Z11-16:Ald, the primary component of sex pheromone in M. separata. Static quenching was observed only between MsepPBP1 and Z9-16:Ald, as well as between MsepPBP3 and Z11-16:Ald or Z9-16:Ald. Transcript levels of MsepPBP1 or MsepPBP3 of male adults were significantly reduced compared to the control when injected with dsMsepPBPs. Both dsPBP1- and dsPBP3-treated males displayed a notable decrease in successful calling behaviors, with this reduction being more pronounced in dsMsepPBP3 injected groups than in dsMsepPBP1 injected groups. These experiments indicated the specificity of MsepPBP1 and MsepPBP3, with both contributing to the sensitivity of female detection. MsepPBP3 appeared to be a key protein for recognizing the sex pheromones of M. separata.

Distinct lineages of the grasshopper Chorthippus parallelus (Orthoptera: Acrididae) form well-known hybrid zones (HZs) both in the Pyrenees and the Alps mountain ranges in South Europe. These HZs represent unique experimental systems to identify "key genes" that maintain genetic boundaries between emerging species. The Iberian endemism C. p. erythropus (Cpe) and the subspecies C. p. parallelus (Cpp), widely distributed throughout the rest of Europe, overlap and form the Pyrenean HZ. Both subspecies differ morphologically, as well as in behavioral, mitochondrial, nuclear, and chromosomal traits, and in the strains of the maternally transmitted bacterial endosymbiont Wolbachia infecting them. This results in either unidirectional and bidirectional cytoplasmic incompatibility between both grasshopper subspecies, pointing out that Wolbachia clearly affects gene expression in the infected individuals. Here we explore how Wolbachia may modify the expression of some major genes involved in relevant pathways in Cpp in the Pyrenean HZ. We have analyzed, through molecular biomarkers, the physiological responses in C. parallelus individuals infected by Wolbachia, with particular attention to the energy metabolism, the immune system response, and the reproduction. qPCR was used to evaluate the expression of selected genes in the gonads of infected and uninfected adults of both sexes, since this tissue constitutes the main target of Wolbachia infection. Transcriptional analyses also showed differential sex-dependent responses in most of the analyzed biomarkers in infected and noninfected individuals. We identified for the first time new sensitive biomarkers that might be involved in the reproductive barrier induced by Wolbachia in the hybrid zone.

The western flower thrips (Frankliniella occidentalis) is a significant agricultural pest, causing severe global yield losses due to extensive feeding damage and the transmission of plant pathogenic viruses. Despite recent advancements in RNA interference (RNAi) in thrips species, its application has been mostly limited to the adult stage. Given the crucial role of first instar larval thrips in acquiring and transmitting orthotospoviruses, achieving gene silencing in these larvae is critical for studying virus entry and acquisition. While thoracic and abdominal injections have proven effective in adult thrips, the low post-injection survival rate hinders their use in larval thrips. This study addresses this challenge by presenting a microinjection methodology to deliver dsRNA into the hemolymph of first instar larval thrips through the coxa, the first proximal segment of the foreleg. This method significantly improved larval survival rate by preventing detrimental damage to the internal tissues. Significant knockdown of V-ATPase-B, cytochrome P450 (CYP3653A2), and apolipophorin-II/I (ApoLp-II/I) transcripts was confirmed after 48 and/or 72 h post injection (hpi), corresponding to the first and second instar larval stages, respectively. Silencing CYP3653A2 or ApoLp-II/I significantly increased larval mortality. These findings demonstrate proof-of-principle of gene silencing and associated silencing phenotype (mortality) for first instar larval thrips and highlight the essential role of CYP3653A2 and ApoLp-II/I in larval vitality. Our RNAi-based tool offers an opportunity to investigate the molecular mechanisms of thrips-orthotospovirus interactions, as the virus must be acquired by young larval thrips for successful transmission to plants, thus presenting potential targets for thrips pest management.

Insecticide contamination and climate change are key factors driving the global decline in insect populations. However, how these factors interact to impact insect survival remains uncertain. In this study, we examined the effects of sex and genotype on the response to long-term low insecticide exposure at two temperatures, 18 °C and 28 °C, using the Drosophila melanogaster model. We focused on a polymorphic gene, Cyp6g1, known for conferring broad insecticide resistance. We found that while temperature and insecticide have a synergistic effect on mortality of susceptible flies (Cyp6g1-M allele), they act additively on resistant flies (Cyp6g1-BA allele). And whereas the mortality of BA flies exposed to insecticides is strongly dependent on sex at 18 °C, no sex bias is found at 28 °C. Under no insecticide exposure, BA females showed shorter median lifespan than males regardless of temperature, possibly reflecting a cost associated with the resistant allele. Surprisingly, across all genotypes, females showed lower Cyp6g1 gene expression levels than males, which contrasts with their higher insecticide tolerance. Temperature and insecticide exposure had small effects on Cyp6g1 expression levels, suggesting the presence of additional mechanisms of resistance. Our results indicate that the effect of high insecticide doses on insect mortality cannot be used to predict how insects will respond to low contaminating doses, especially when considering the strong interactions between sex, temperature, and genotype. The combined effects of temperature and long-term low insecticide exposure are complex and can have major impacts on insect population dynamics and survival.

Carbon dioxide (CO₂) plays a crucial role in the host search/localization process of bed bugs, Cimex lectularius L., and Cimex hemipterus (F.). Current research on the CO₂ perception by bed bugs mainly focuses on their behavioral responses, and the molecular mechanisms are still unclear. In addition, existing research has mainly been conducted on C. lectularius with very little research on C. hemipterus. In this study, we investigated the behavioral response of C. hemipterus to CO₂ and analyzed the role of antennae in the CO₂ sensing process. Then, potential CO₂ receptor genes were screened through antennal RNA sequencing and tissue-specific expression profiling analysis. Finally, the function of CO₂ receptors was further validated using RNA interference. Results indicated that increasing the CO₂ concentration in the air not only stimulated the activity of C. hemipterus, but also presented a directional attraction effect on them. CO₂, with a concentration of 0.06%-1.8%, had a significant attraction effect on C. hemipterus. Removal of the antennae led to the loss of bed bugs' preference for CO₂. Four candidate CO₂ receptor genes (ChGR1, ChGR2, ChGR3, and ChGR4) were identified through transcriptomic analysis of the bed bug antennae, and 3 of them (ChGR2, ChGR3, and ChGR4) were highly expressed in the antennae. Silencing ChGR2 or ChGR4 individually led to a significant reduction or even loss of CO₂ sensing ability in C. hemipterus. In conclusion, CO₂ can induce the host searching behavior of C. hemipterus; moreover, ChGR2 and ChGR4 are crucial for detecting CO₂ in C. hemipterus.

Harmonia axyridis was originally considered and used as a biocontrol agent throughout the world. But its effectiveness has turned into a serious detriment to ecosystems, as it has become an invasive and harmful species, gradually displacing native coccinellid populations. Its invasive success mostly relies on its voracity, aggressiveness, and dominance in intraguild predation (IGP) interactions. Aggressiveness is a major behavioral characteristic known to influence IGP occurrence and outcome. So, what if H. axyridis were confronted with more aggressive competitors? To understand the vulnerability of H. axyridis to aggressive competitors, we confronted it with an IGP interaction involving two artificially selected lines of the generalist predator Nabis americoferus (one aggressive and one docile) in the presence of extraguild prey (Myzus persicae). Two hypotheses were formulated: (1) the IGP intensity toward H. axyridis is positively correlated with the intraguild predator's aggressiveness, and (2) the IGP intensity decreases in the presence of extraguild prey for both the aggressive and docile lines. Results showed that, as expected, the aggressive line displayed a higher IGP rate on H. axyridis than the docile line, supporting the first hypothesis. The second hypothesis was also supported, since extraguild prey availability led to a decrease in IGP for both lines. Apart from providing insights into the relationship between aggressiveness and IGP occurrence, the discussion focuses on the consequences for H. axyridis in the field as an invasive species and as a biological control agent.

Pests are a major cause of agricultural and economic losses. Their high reproduction rate remains a considerable challenge for pest control. Insects with impaired border cell migration during oogenesis are unable to reproduce, offering a potential method to reduce their population growth. To fully understand the effects of the deubiquitinating enzyme (DUB) family on border cell migration, we generated 38 transgenic fly lines overexpressing distinct DUBs, using Gal4/UAS technology to drive their expression in border cells. Overexpression of usp10 led to reductions in ovary size, egg production, and egg hatchability. Interestingly, knockdown of usp10 also resulted in the same defects, indicating the importance of maintaining proper Usp10 levels for oogenesis. In addition, the immunofluorescence and confocal microscopy analysis revealed that either overexpression or knockdown of usp10 disrupts adherens junctions and actin filament distribution, ultimately leading to delayed border cell migration. Taken together, this study highlights the critical role of Usp10 in Drosophila fertility, and suggests Usp10 as a potential target for pest management.